Parking Lot Resurfacing Soweto

For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Parking Lot Resurfacing in Soweto except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

Commercial Paving Cost Estimate

Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

Asphalt Paving Cost Estimate

The primary use (70%) of asphalt Asphalt Driveway Sealing Cost is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

Driveway

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Parking Lot Resurfacing Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

Asphalt Driveway Repair Price

The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Asphalt Millings Driveway the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

Asphalt Repair Cost Estimate

The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Sidewalk

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

Driveway Paving Cost Estimate

In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

Asphalt Paving Cost Estimate

Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

Asphalt Driveway Price

The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

Paving Specialists Price

Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

Concrete

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

Paving Specialists Price

Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

Residential Paving Companies Quotes

Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

Asphalt Repair Price

The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

Paving Companies Quotes

The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

Asphalt Driveway Costs

In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

Residential Paving Cost Estimate

In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

Driveway

Asphalt Driveway Paving Price

An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

Paving Contractors Costs

But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

Asphalt Paving Cost Estimate

The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

Macadam

Asphalt Driveway Paving Price

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

Parking Lot Resurfacing in Soweto ?

Asphalt Surfacing Company Cost Estimate For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)mən, bˈt(j)mən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.[3] The word is derived from the Ancient Greek ἄσφαλτος ásphaltos.[4]

The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.[5]

The terms "asphalt" and "bitumen" are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" (or "asphalt cement") is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called "bitumen", and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.

Naturally occurring asphalt is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.[8]

The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch",[9] which perhaps derives from ἀ-, "without" and σφάλλω (sfallō), "make fall".[10] The first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads.

The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", and jatu-krit, meaning "pitch creating" or "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.[12]

In British English, "bitumen" is used instead of "asphalt". The word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called "tarmac" in common parlance). Bitumen mixed with clay was usually called "asphaltum",[13] but the term is less commonly used today.[citation needed]

In Australian English, "bitumen" is often used as the generic term for road surfaces.

In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is also commonly used as a shortened form of "asphalt concrete" (therefore equivalent to the British "asphalt" or "tarmac").

In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while "asphalt" is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", and syncrude blended with bitumen is called "synbit".[15]

"Bitumen" is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

Neither of the terms "asphalt" or "bitumen" should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.[5]

The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] "It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".[17]

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word "tarmac", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US. The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.[8]

The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.[21]

Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.[19]

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.[22]

Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.[21]

The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.[26]

The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.[27]

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians' primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.[31]

In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.[21]

In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.[33]

An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".[34]

But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.[36]

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon's Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.[38]

The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.[36]

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge.[35][44][45][46] Claridge's Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France",[47]—"laid one of the first asphalt pavements in Whitehall".[48] Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,[47][49] "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park".[49] "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry".[45] "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production",[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".[51]

In 1838, there was a flurry of entrepreneurial activity involving asphalt, which had uses beyond paving. For example, asphalt could also be used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, both of which were also proliferating in the 19th century.[3][35][52] On the London stockmarket, there were various claims as to the exclusivity of asphalt quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s".[50]

In 1914, Claridge's Company entered into a joint venture to produce tar-bound macadam,[53] with materials manufactured through a subsidiary company called Clarmac Roads Ltd.[54] Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridge's Patent Asphalte Co., although Clarmac was more widely used.[55][note 1] However, the First World War ruined the Clarmac Company, which entered into liquidation in 1915.[57][58] The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up,[59] ceasing operations in 1917,[60][61] having invested a substantial amount of funds into the new venture, both at the outset[59] and in a subsequent attempt to save the Clarmac Company.[57]

The first use of bitumen in the New World was by indigenous peoples. On the west coast, as early as the 13th century, the Tongva, Luiseño and Chumash peoples collected the naturally occurring bitumen that seeped to the surface above underlying petroleum deposits. All three groups used the substance as an adhesive. It is found on many different artifacts of tools and ceremonial items. For example, it was used on rattles to adhere gourds or turtle shells to rattle handles. It was also used in decorations. Small round shell beads were often set in asphaltum to provide decorations. It was used as a sealant on baskets to make them watertight for carrying water, possibly poisoning those who drank the water.[62] Asphalt was used also to seal the planks on ocean-going canoes.

Asphalt was first used to pave streets in the 1870s. At first naturally occurring "bituminous rock" was used, such as at Ritchie Mines in Macfarlan in Ritchie County, West Virginia from 1852 to 1873. In 1876, asphalt-based paving was used to pave Pennsylvania Avenue in Washington DC, in time for the celebration of the national centennial.[63] In the horse-drawn era, streets were unpaved and covered with dirt or gravel. However, that produced uneven wear, opened new hazards for pedestrians and made for dangerous potholes for bicycles and for motor vehicles. Manhattan alone had 130,000 horses in 1900, pulling streetcars, wagons, and carriages, and leaving their waste behind. They were not fast, and pedestrians could dodge and scramble their way across the crowded streets. Small towns continued to rely on dirt and gravel, but larger cities wanted much better streets. They looked to wood or granite blocks by the 1850s.[64] In 1890, a third of Chicago's 2000 miles of streets were paved, chiefly with wooden blocks, which gave better traction than mud. Brick surfacing was a good compromise, but even better was asphalt paving, which was easy to install and to cut through to get at sewers. With London and Paris serving as models, Washington laid 400,000 square yards of asphalt paving by 1882; it became the model for Buffalo, Philadelphia and elsewhere. By the end of the century, American cities boasted 30 million square yards of asphalt paving, well ahead of brick.[65] The streets became faster and more dangerous so electric traffic lights were installed. Electric trolleys (at 12 miles per hour) became the main transportation service for middle class shoppers and office workers until they bought automobiles after 1945 and commuted from more distant suburbs in privacy and comfort on asphalt highways.[66]

See also: Bitumount and History of the petroleum industry in Canada (oil sands and heavy oil)

Canada has the world's largest deposit of natural bitumen in the Athabasca oil sands, and Canadian First Nations along the Athabasca River had long used it to waterproof their canoes. In 1719, a Cree named Wa-Pa-Su brought a sample for trade to Henry Kelsey of the Hudson’s Bay Company, who was the first recorded European to see it. However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."[21]

The value of the deposit was obvious from the start, but the means of extracting the bitumen was not. The nearest town, Fort McMurray, Alberta, was a small fur trading post, other markets were far away, and transportation costs were too high to ship the raw bituminous sand for paving. In 1915, Sidney Ells of the Federal Mines Branch experimented with separation techniques and used the product to pave 600 feet of road in Edmonton, Alberta. Other roads in Alberta were paved with material extracted from oil sands, but it was generally not economic. During the 1920s Dr. Karl A. Clark of the Alberta Research Council patented a hot water oil separation process and entrepreneur Robert C. Fitzsimmons[67] built the Bitumount oil separation plant, which between 1925 and 1958 produced up to 300 barrels (50 m3) per day of bitumen using Dr. Clark's method. Most of the bitumen was used for waterproofing roofs, but other uses included fuels, lubrication oils, printers ink, medicines, rust- and acid-proof paints, fireproof roofing, street paving, patent leather, and fence post preservatives.[21] Eventually Fitzsimmons ran out of money and the plant was taken over by the Alberta government. Today the Bitumount plant is a Provincial Historic Site.[68]

Bitumen was used in early photographic technology. In 1826 or 1827, it was used by French scientist Joseph Nicéphore Niépce to make the oldest surviving photograph from nature. The bitumen was thinly coated onto a pewter plate which was then exposed in a camera. Exposure to light hardened the bitumen and made it insoluble, so that when it was subsequently rinsed with a solvent only the sufficiently light-struck areas remained. Many hours of exposure in the camera were required, making bitumen impractical for ordinary photography, but from the 1850s to the 1920s it was in common use as a photoresist in the production of printing plates for various photomechanical printing processes.[69][70]

Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle.[71]

The vast majority of refined asphalt is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use, asphalt is produced to specification. This is achieved either by refining or blending. It is estimated that the current world use of asphalt is approximately 102 million tonnes per year. Approximately 85% of all the asphalt produced is used as the binder in asphalt concrete for roads. It is also used in other paved areas such as airport runways, car parks and footways. Typically, the production of asphalt concrete involves mixing fine and coarse aggregates such as sand, gravel and crushed rock with asphalt, which acts as the binding agent. Other materials, such as recycled polymers (e.g., rubber tyres), may be added to the asphalt to modify its properties according to the application for which the asphalt is ultimately intended.

A further 10% of global asphalt production is used in roofing applications, where its waterproofing qualities are invaluable. The remaining 5% of asphalt is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet tile backing and paint. Asphalt is applied in the construction and maintenance of many structures, systems, and components, such as the following:

Main article: Asphalt concrete

The largest use of asphalt is for making asphalt concrete for road surfaces; this accounts for approximately 85% of the asphalt consumed in the United States. Asphalt concrete pavement mixes are typically composed of 5% asphalt cement and 95% aggregates (stone, sand, and gravel). Due to its highly viscous nature, asphalt cement must be heated so it can be mixed with the aggregates at the asphalt mixing facility. The temperature required varies depending upon characteristics of the asphalt and the aggregates, but warm-mix asphalt technologies allow producers to reduce the temperature required. There are about 4,000 asphalt concrete mixing plants in the US, and a similar number in Europe.[72]

When maintenance is performed on asphalt pavements, such as milling to remove a worn or damaged surface, the removed material can be returned to a facility for processing into new pavement mixtures. The asphalt in the removed material can be reactivated and put back to use in new pavement mixes.[73] With some 95% of paved roads being constructed of or surfaced with asphalt,[74] a substantial amount of asphalt pavement material is reclaimed each year. According to industry surveys conducted annually by the Federal Highway Administration and the National Asphalt Pavement Association, more than 99% of the asphalt removed each year from road surfaces during widening and resurfacing projects is reused as part of new pavements, roadbeds, shoulders and embankments.[75]

Asphalt concrete paving is widely used in airports around the world. Due to the sturdiness and ability to be repaired quickly, it is widely used for runways.

Further information: Fibre mastic asphalt

Mastic asphalt is a type of asphalt that differs from dense graded asphalt (asphalt concrete) in that it has a higher asphalt (binder) content, usually around 7–10% of the whole aggregate mix, as opposed to rolled asphalt concrete, which has only around 5% asphalt. This thermoplastic substance is widely used in the building industry for waterproofing flat roofs and tanking underground. Mastic asphalt is heated to a temperature of 210 °C (410 °F) and is spread in layers to form an impervious barrier about 20 millimeters (0.8 inches) thick.

A number of technologies allow asphalt to be mixed at much lower temperatures. These involve mixing with petroleum solvents to form "cutbacks" with reduced melting point or mixing with water to turn the asphalt into an emulsion. Asphalt emulsions contain up to 70% asphalt and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock, gravel or crushed slag. Slurry seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on the surface of a road. Cold-mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth, and asphalt emulsions are also blended into recycled hot-mix asphalt to create low-cost pavements.

Main article: Synthetic crude oil See also: Petroleum production in Canada

Synthetic crude oil, also known as syncrude, is the output from a bitumen upgrader facility used in connection with oil sand production in Canada. Bituminous sands are mined using enormous (100 ton capacity) power shovels and loaded into even larger (400 ton capacity) dump trucks for movement to an upgrading facility. The process used to extract the bitumen from the sand is a hot water process originally developed by Dr. Karl Clark of the University of Alberta during the 1920s. After extraction from the sand, the bitumen is fed into a bitumen upgrader which converts it into a light crude oil equivalent. This synthetic substance is fluid enough to be transferred through conventional oil pipelines and can be fed into conventional oil refineries without any further treatment. By 2015 Canadian bitumen upgraders were producing over 1 million barrels (160×10^3 m3) per day of synthetic crude oil, of which 75% was exported to oil refineries in the United States.[76]

In Alberta, five bitumen upgraders produce synthetic crude oil and a variety of other products: The Suncor Energy upgrader near Fort McMurray, Alberta produces synthetic crude oil plus diesel fuel; the Syncrude Canada, Canadian Natural Resources, and Nexen upgraders near Fort McMurray produce synthetic crude oil; and the Shell Scotford Upgrader near Edmonton produces synthetic crude oil plus an intermediate feedstock for the nearby Shell Oil Refinery.[77] A sixth upgrader, under construction in 2015 near Redwater, Alberta, will upgrade half of its crude bitumen directly to diesel fuel, with the remainder of the output being sold as feedstock to nearby oil refineries and petrochemical plants.[78]

See also: Western Canadian Select

Canadian bitumen does not differ substantially from oils such as Venezuelan extra-heavy and Mexican heavy oil in chemical composition, and the real difficulty is moving the extremely viscous bitumen through oil pipelines to the refinery. Many modern oil refineries are extremely sophisticated and can process non-upgraded bitumen directly into products such as gasoline, diesel fuel, and refined asphalt without any preprocessing. This is particularly common in areas such as the US Gulf coast, where refineries were designed to process Venezuelan and Mexican oil, and in areas such as the US Midwest where refineries were rebuilt to process heavy oil as domestic light oil production declined. Given the choice, such heavy oil refineries usually prefer to buy bitumen rather than synthetic oil because the cost is lower, and in some cases because they prefer to produce more diesel fuel and less gasoline.[77] By 2015 Canadian production and exports of non-upgraded bitumen exceeded that of synthetic crude oil at over 1.3 million barrels (210×10^3 m3) per day, of which about 65% was exported to the United States.[76]

Because of the difficulty of moving crude bitumen through pipelines, non-upgraded bitumen is usually diluted with natural-gas condensate in a form called dilbit or with synthetic crude oil, called synbit. However, to meet international competition, much non-upgraded bitumen is now sold as a blend of multiple grades of bitumen, conventional crude oil, synthetic crude oil, and condensate in a standardized benchmark product such as Western Canadian Select. This sour, heavy crude oil blend is designed to have uniform refining characteristics to compete with internationally marketed heavy oils such as Mexican Mayan or Arabian Dubai Crude.[77]

Asphalt was used starting in the 1960s as an hydrophobic matrix aiming to encapsulate radioactive waste such as medium-activity salts (mainly soluble sodium nitrate and sodium sulfate) produced by the reprocessing of spent nuclear fuels or radioactive sludges from sedimentation ponds.[79][80] Bituminised radioactive waste containing highly radiotoxic alpha-emitting transuranic elements from nuclear reprocessing plants have been produced at industrial scale in France, Belgium and Japan, but this type of waste conditioning has been abandoned because operational safety issues (risks of fire, as occurred in a bituminisation plant at Tokai Works in Japan)[81][82] and long-term stability problems related to their geological disposal in deep rock formations. One of the main problem is the swelling of asphalt exposed to radiation and to water. Asphalt swelling is first induced by radiation because of the presence of hydrogen gas bubbles generated by alpha and gamma radiolysis.[83][84] A second mechanism is the matrix swelling when the encapsulated hygroscopic salts exposed to water or moisture start to rehydrate and to dissolve. The high concentration of salt in the pore solution inside the bituminised matrix is then responsible for osmotic effects inside the bituminised matrix. The water moves in the direction of the concentrated salts, the asphalt acting as a semi-permeable membrane. This also causes the matrix to swell. The swelling pressure due to osmotic effect under constant volume can be as high as 200 bar. If not properly managed, this high pressure can cause fractures in the near field of a disposal gallery of bituminised medium-level waste. When the bituminised matrix has been altered by swelling, encapsulated radionuclides are easily leached by the contact of ground water and released in the geosphere. The high ionic strength of the concentrated saline solution also favours the migration of radionuclides in clay host rocks. The presence of chemically reactive nitrate can also affect the redox conditions prevailing in the host rock by establishing oxidizing conditions, preventing the reduction of redox-sensitive radionuclides. Under their higher valences, radionuclides of elements such as selenium, technetium, uranium, neptunium and plutonium have a higher solubility and are also often present in water as non-retarded anions. This makes the disposal of medium-level bituminised waste very challenging.

Different type of asphalt have been used: blown bitumen (partly oxidized with air oxygen at high temperature after distillation, and harder) and direct distillation bitumen (softer). Blown bitumens like Mexphalte, with a high content of saturated hydrocarbons, are more easily biodegraded by microorganisms than direct distillation bitumen, with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons.[85]

Concrete encapsulation of radwaste is presently considered a safer alternative by the nuclear industry and the waste management organisations.

Roofing shingles account for most of the remaining asphalt consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Asphalt is used to make Japan black, a lacquer known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker.[86] Asphalt is also used to seal some alkaline batteries during the manufacturing process.

Typical asphalt plant for making asphalt

About 40,000,000 tons were produced in 1984.[needs update] It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as naphtha, gasoline and diesel). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude asphalt is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This step makes the product harder and more viscous.[5]

Asphalt is typically stored and transported at temperatures around 150 °C (302 °F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.

Main article: Oil sands

Naturally occurring crude bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from "oil sands", currently under development in Alberta, Canada. Canada has most of the world's supply of natural bitumen, covering 140,000 square kilometres[14] (an area larger than England), giving it the second-largest proven oil reserves in the world. The Athabasca oil sands are the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods. Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020.[15] The total amount of crude bitumen in Alberta that could be extracted is estimated to be about 310 billion barrels (50×10^9 m3),[8] which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.

Main articles: Peak oil, Global warming, and Bioasphalt

Although uncompetitive economically, asphalt can be made from nonpetroleum-based renewable resources such as sugar, molasses and rice, corn and potato starches. Asphalt can also be made from waste material by fractional distillation of used motor oil, which is sometimes otherwise disposed of by burning or dumping into landfills. Use of motor oil may cause premature cracking in colder climates, resulting in roads that need to be repaved more frequently.[87]

Nonpetroleum-based asphalt binders can be made light-colored. Lighter-colored roads absorb less heat from solar radiation, reducing their contribution to the urban heat island effect.[88] Parking lots that use asphalt alternatives are called green parking lots.

Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania, the only European asphalt mine still in use. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring and ball) around 120 °C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.

Albanian bitumen extraction has a long history and was practiced in an organized way by the Romans. After centuries of silence, the first mentions of Albanian bitumen appeared only in 1868, when the Frenchman Coquand published the first geological description of the deposits of Albanian bitumen. In 1875, the exploitation rights were granted to the Ottoman government and in 1912, they were transferred to the Italian company Simsa. Since 1945, the mine was exploited by the Albanian government and from 2001 to date, the management passed to a French company, which organized the mining process for the manufacture of the natural bitumen on an industrial scale.[89]

Today the mine is predominantly exploited in an open pit quarry but several of the many underground mines (deep and extending over several km) still remain viable. Selenizza is produced primarily in granular form, after melting the bitumen pieces selected in the mine.

Selenizza[90] is mainly used as an additive in the road construction sector. It is mixed with traditional asphalt to improve both the viscoelastic properties and the resistance to ageing. It may be blended with the hot asphalt in tanks, but its granular form allows it to be fed in the mixer or in the recycling ring of normal asphalt plants. Other typical applications include the production of mastic asphalts for sidewalks, bridges, car-parks and urban roads as well as drilling fluid additives for the oil and gas industry. Selenizza is available in powder or in granular material of various particle sizes and is packaged in sacks or in thermal fusible polyethylene bags.

A life-cycle assessment study of the natural selenizza compared with petroleum asphalt has shown that the environmental impact of the selenizza is about half the impact of the road asphalt produced in oil refineries in terms of carbon dioxide emission.[91]

People can be exposed to asphalt in the workplace by breathing in fumes or skin absorption. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit of 5 mg/m3 over a 15-minute period.[92]

Asphalt is basically an inert material that must be heated or diluted to a point where it becomes workable for the production of materials for paving, roofing, and other applications. In examining the potential health hazards associated with asphalt, the International Agency for Research on Cancer (IARC) determined that it is the application parameters, predominantly temperature, that affect occupational exposure and the potential bioavailable carcinogenic hazard/risk of the asphalt emissions.[93] In particular, temperatures greater than 199 °C (390 °F), were shown to produce a greater exposure risk than when asphalt was heated to lower temperatures, such as those typically used in asphalt pavement mix production and placement.[94] IARC has classified asphalt as a Class 2B possible carcinogen.

An asphalt mixing plant for hot aggregate
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  38. ^ Salmon, William (1685), Polygraphice; Or, The Arts of Drawing, Engraving, Etching, Limning, Painting, Washing, Varnishing, Gilding, Colouring, Dying, Beautifying and Perfuming (5th ed.), London: R. Jones, pp. 76–77, retrieved 18 August 2010  Text at Internet Archive
  39. ^ "Specification of the Patent granted to Richard Tappin Claridge, of the County of Middlesex, for a Mastic Cement, or Composition applicable to Paving and Road making, covering Buildings and various purposes". Journal of the Franklin Institute of the State of Pennsylvania and Mechanics' Register. Vol. 22. London: Pergamon Press. July 1838. pp. 414–418. Retrieved 18 November 2009. 
  40. ^ "Comments on asphalt patents of R.T. Claridge, Esq". Notes and Queries: A medium of intercommunication for Literary Men, General Readers, etc. Ninth series. Volume XII, July–December, 1903 (9th S. XII, 4 July 1903). London: John C. Francis. 20 January 1904. pp. 18–19.  Writer is replying to note or query from previous publication, cited as 9th S. xi. 30
  41. ^ "Obituary of Frederick Walter Simms". Monthly Notices of the Royal Astronomical Society. London: Strangeways & Walden. XXVI: 120–121. November 1865 – June 1866. Retrieved 12 November 2009. 
  42. ^ Broome, D.C. (1963). "The development of the modern asphalt road". The Surveyor and municipal and county engineer. London. 122 (3278 & 3279): 1437–1440 & 1472–1475Snippet view: Simms & Claridge p.1439 
  43. ^ Phipson, Dr T. Lamb (1902). Confessions of a Violinist: Realities and Romance. London: Chatto & Windus. p. 11. Retrieved 26 November 2009.  Full text at Internet Archive (archive.org)
  44. ^ "Claridge's UK Patents in 1837 & 1838". The London Gazette. 25 February 1851. p. 489. 
  45. ^ a b Hobhouse, Hermione (General Editor) (1994). "British History Online". 'Northern Millwall: Tooke Town', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs. pp. 423–433 (see text at refs 169 & 170). Retrieved 8 November 2009. 
  46. ^ "Claridge's Scottish and Irish Patents in 1838". The Mechanic's magazine, museum, register, journal and gazette. 29. London: W.A. Robertson. 7 April – 29 September 1838. pp. vii, viii, 64, 128. 
  47. ^ a b "Joint Stock Companies (description of asphalte use by Claridge's company)". The Civil Engineer and Architects Journal. Vol. 1. London. October 1837 – December 1838. p. 199. Retrieved 16 November 2009.  Full text at Internet Archive (archive.org). Alternative viewing at: https://books.google.com/books?id=sQ5AAAAAYAAJ&pg
  48. ^ Miles, Lewis (2000), pp.10.06.1–2
  49. ^ a b Comments on asphalt patents of R.T. Claridge, Esq (1904), p.18
  50. ^ a b Miles, Lewis (2000), p.10.06.2
  51. ^ "1838 bitumen UK uses by Robinson's and Claridge's companies, & the Bastenne company". The Mechanic's magazine, museum, register, journal and gazette. 29. London: W.A. Robertson. 22 September 1838. p. 448. 
  52. ^ Gerhard, W.M. Paul (1908). Modern Baths and Bath Houses (1st ed.). New York: John Wiley and Sons.  (Enter "asphalt" into the search field for list of pages discussing the subject)
  53. ^ "Claridge's Patent Asphalte Co. ventures into tarred slag macadam", Concrete and Constructional Engineering, London, IX (1): 760, January 1914, retrieved 15 June 2010 
  54. ^ "Registration of Clarmac Roads", The Law Reports: Chancery Division, Vol. 1: 544–547, 1921, retrieved 17 June 2010 
  55. ^ "Clarmac and Clarphalte", The Building News and Engineering Journal, Vol. 109: July to December 1915 (No. 3157): 2–4 (n13–15 in electronic page field), 7 July 1915, retrieved 18 June 2010 
  56. ^ Roads laid with Clarmac The Building News and Engineering Journal, 1915 109 (3157), p.3 (n14 in electronic field).
  57. ^ a b Clarmac financial difficults due to WW1 Debentures deposited The Law Reports: Chancery Division, (1921) Vol. 1 p.545. Retrieved 17 June 2010.
  58. ^ "Notice of the Winding up of Clarmac Roads", The London Gazette (29340): 10568, 26 October 1915, retrieved 15 June 2010 
  59. ^ a b Claridge's Patent Asphalte Co. compulsorily wound up Funds invested in new company The Law Times Reports (1921) Vol.125, p.256. Retrieved 15 June 2010.
  60. ^ "Claridge's Patent Asphalte Co. winds up 10 November 1917". The London Gazette. 16 November 1917. p. 11863. 
  61. ^ Hobhouse, Hermione (General Editor) (1994). "British History Online". 'Cubitt Town: Riverside area: from Newcastle Drawdock to Cubitt Town Pier', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs. pp. 528–532 (see text at refs 507 & 510). Retrieved 8 November 2009. 
  62. ^ Stockton, Nick (23 June 2017). "Plastic Water Bottles Might Have Poisoned Ancient Californians". Wired. Retrieved 26 June 2017. 
  63. ^ McNichol, Dan (2005). Paving the Way: Asphalt in America. Lanham, MD: National Asphalt Pavement Association. ISBN 0-914313-04-5. Archived from the original on 2006-08-29. 
  64. ^ David O. Whitten, "A Century of Parquet Pavements: Wood as a Paving Material In The United States And Abroad, 1840-1940." Essays in Economic and Business History 15 (1997): 209-26.
  65. ^ Arthur Maier Schlesinger, The Rise of the City: 1878-1898 (1933) p 88-93.
  66. ^ John D. Fairfield, "Rapid Transit: Automobility and Settlement in Urban America" Reviews in American History 23#1 (1995), pp. 80-85 online.
  67. ^ "Robert C. Fitzsimmons (1881–1971)". Canadian Petroleum Hall of Fame. 2010. Retrieved 2016-01-20. 
  68. ^ "Bitumount". Government of Alberta. 2016. Retrieved 2016-01-20. 
  69. ^ Niépce Museum history pages. Retrieved 27 October 2012. Archived 3 August 2007 at the Wayback Machine.
  70. ^ The First Photograph (Harry Ransom Center, University of Texas at Austin). Retrieved 27 October 2012.
  71. ^ Spiegelman, Willard (2009-08-21). "Revolutionary Romanticism: 'The Raft of the Medusa' brought energy to French art". The Wall Street Journal. New York City. Retrieved 2016-01-27. 
  72. ^ The Asphalt Paving Industry: A Global Perspective, 2nd Edition (PDF). Lanham, Maryland, and Brussels: National Asphalt Pavement Association and European Asphalt Pavement Association. February 2011. ISBN 0-914313-06-1. Retrieved 27 September 2012. 
  73. ^ "How Should We Express RAP and RAS Contents?". Asphalt Technology E-News. 26 (2). 2014. Archived from the original on 9 June 2015. Retrieved 2015-08-13. 
  74. ^ "Highway Statistics Series: Public Road Length Miles by Type of Surface and Ownership". Federal Highway Administration. 2013-10-01. Retrieved 2015-08-13. 
  75. ^ "Asphalt Pavement Recycling". Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2009–2013. National Asphalt Pavement Association. Retrieved 13 August 2015. 
  76. ^ a b "Crude Oil and Petroleum Products". National Energy Board of Canada. Retrieved January 21, 2016. 
  77. ^ a b c "2015 CAPP Crude Oil Forecast, Markets & Transportation". Canadian Association of Petroleum Producers. Archived from the original on 20 January 2016. Retrieved January 21, 2016. 
  78. ^ "The Project". North West Redwater Partnership. Retrieved January 21, 2016. 
  79. ^ Rodier, J., Scheidhauer, J., & Malabre, M. (1961). The conditioning of radioactive waste by bitumen (No. CEA-R—1992). CEA Marcoule.
  80. ^ Lefillatre, G., Rodier, J., Hullo, R., Cudel, Y., & Rodi, L. (1969). Use of a thin-film evaporator for bitumen coating of radioactive concentrates (No. CEA-R—3742). CEA Marcoule.
  81. ^ Sato, Y., Miura, A., Kato, Y., Suzuki, H., Shigetome, Y., Koyama, T., ... & Yamanouchi, T. (2000). Study on the cause of the fire and explosion incident at Bituminization Demonstration Facility of PNC Tokai Works. In Nuclear waste: from research to industrial maturity. International conference (pp. 179–190).
  82. ^ Okada, K., Nur, R. M., & Fujii, Y. (1999). The formation of explosive compounds in bitumen/nitrate mixtures. Journal of hazardous materials, 69(3), 245–256.
  83. ^ Johnson, D.I., Hitchon, J.W., & Phillips, D.C. (1986). Further observations of the swelling of bitumens and simulated bitumen wasteforms during γ-irradiation (No. AERE-R—12292). UKAEA Harwell Lab. Materials Development Division.
  84. ^ Phillips, D. C., Hitchon, J. W., Johnson, D. I., & Matthews, J. R. (1984). The radiation swelling of bitumens and bitumenised wastes. Journal of nuclear materials, 125(2), 202–218.
  85. ^ Ait-Langomazino, N., Sellier, R., Jouquet, G., & Trescinski, M. (1991). Microbial degradation of bitumen. Experientia, 47(6), 533–539.
  86. ^ Mohd, Meraj Jafri; Singh, D. K. (march 2013). "Cashew Nutshell Liquid Resin" (PDF). IJRREST: International Journal of Research Review in Engineering Science and Technology. 2: 60–65.  Check date values in: |date= (help)
  87. ^ Hesp, Simon A.M.; Herbert F. Shurvell (2010). "X-ray fluorescence detection of waste engine oil residue in asphalt and its effect on cracking in service". International Journal of Pavement Engineering. 11 (6): 541–553. doi:10.1080/10298436.2010.488729. ISSN 1029-8436. Retrieved 2014-03-24. 
  88. ^ Heat Island Effect. From the website of the US Environmental Protection Agency.
  89. ^ Giavarini, Carlo (March 2013). Six Thousand Years of Asphalt. SITEB. pp. 71–78. ISBN 978-88-908408-3-8. 
  90. ^ [3], Selenice Bitumi for more information about Selenizza
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  94. ^ Cavallari, J. M.; Zwack, L. M.; Lange, C. R.; Herrick, R. F.; Mcclean, M. D. (2012). "Temperature-Dependent Emission Concentrations of Polycyclic Aromatic Hydrocarbons in Paving and Built-Up Roofing Asphalts". Annals of Occupational Hygiene. 56 (2): 148–160. doi:10.1093/annhyg/mer107 . ISSN 0003-4878. 
  95. ^ "Contacto – Eco Roofing". epdmecoroofing.com. 
  96. ^ "Follow the evolution of the road from path to pavement". 


Michigan left

Paving Specialists Near Me For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)mən, bˈt(j)mən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.[3] The word is derived from the Ancient Greek ἄσφαλτος ásphaltos.[4]

The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.[5]

The terms "asphalt" and "bitumen" are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" (or "asphalt cement") is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called "bitumen", and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.

Naturally occurring asphalt is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.[8]

The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch",[9] which perhaps derives from ἀ-, "without" and σφάλλω (sfallō), "make fall".[10] The first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads.

The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", and jatu-krit, meaning "pitch creating" or "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.[12]

In British English, "bitumen" is used instead of "asphalt". The word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called "tarmac" in common parlance). Bitumen mixed with clay was usually called "asphaltum",[13] but the term is less commonly used today.[citation needed]

In Australian English, "bitumen" is often used as the generic term for road surfaces.

In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is also commonly used as a shortened form of "asphalt concrete" (therefore equivalent to the British "asphalt" or "tarmac").

In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while "asphalt" is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", and syncrude blended with bitumen is called "synbit".[15]

"Bitumen" is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

Neither of the terms "asphalt" or "bitumen" should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.[5]

The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] "It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".[17]

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word "tarmac", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US. The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.[8]

The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.[21]

Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.[19]

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.[22]

Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.[21]

The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.[26]

The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.[27]

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians' primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.[31]

In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.[21]

In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.[33]

An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".[34]

But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.[36]

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon's Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.[38]

The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.[36]

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge.[35][44][45][46] Claridge's Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France",[47]—"laid one of the first asphalt pavements in Whitehall".[48] Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,[47][49] "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park".[49] "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry".[45] "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production",[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".[51]

In 1838, there was a flurry of entrepreneurial activity involving asphalt, which had uses beyond paving. For example, asphalt could also be used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, both of which were also proliferating in the 19th century.[3][35][52] On the London stockmarket, there were various claims as to the exclusivity of asphalt quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s".[50]

In 1914, Claridge's Company entered into a joint venture to produce tar-bound macadam,[53] with materials manufactured through a subsidiary company called Clarmac Roads Ltd.[54] Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridge's Patent Asphalte Co., although Clarmac was more widely used.[55][note 1] However, the First World War ruined the Clarmac Company, which entered into liquidation in 1915.[57][58] The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up,[59] ceasing operations in 1917,[60][61] having invested a substantial amount of funds into the new venture, both at the outset[59] and in a subsequent attempt to save the Clarmac Company.[57]

The first use of bitumen in the New World was by indigenous peoples. On the west coast, as early as the 13th century, the Tongva, Luiseño and Chumash peoples collected the naturally occurring bitumen that seeped to the surface above underlying petroleum deposits. All three groups used the substance as an adhesive. It is found on many different artifacts of tools and ceremonial items. For example, it was used on rattles to adhere gourds or turtle shells to rattle handles. It was also used in decorations. Small round shell beads were often set in asphaltum to provide decorations. It was used as a sealant on baskets to make them watertight for carrying water, possibly poisoning those who drank the water.[62] Asphalt was used also to seal the planks on ocean-going canoes.

Asphalt was first used to pave streets in the 1870s. At first naturally occurring "bituminous rock" was used, such as at Ritchie Mines in Macfarlan in Ritchie County, West Virginia from 1852 to 1873. In 1876, asphalt-based paving was used to pave Pennsylvania Avenue in Washington DC, in time for the celebration of the national centennial.[63] In the horse-drawn era, streets were unpaved and covered with dirt or gravel. However, that produced uneven wear, opened new hazards for pedestrians and made for dangerous potholes for bicycles and for motor vehicles. Manhattan alone had 130,000 horses in 1900, pulling streetcars, wagons, and carriages, and leaving their waste behind. They were not fast, and pedestrians could dodge and scramble their way across the crowded streets. Small towns continued to rely on dirt and gravel, but larger cities wanted much better streets. They looked to wood or granite blocks by the 1850s.[64] In 1890, a third of Chicago's 2000 miles of streets were paved, chiefly with wooden blocks, which gave better traction than mud. Brick surfacing was a good compromise, but even better was asphalt paving, which was easy to install and to cut through to get at sewers. With London and Paris serving as models, Washington laid 400,000 square yards of asphalt paving by 1882; it became the model for Buffalo, Philadelphia and elsewhere. By the end of the century, American cities boasted 30 million square yards of asphalt paving, well ahead of brick.[65] The streets became faster and more dangerous so electric traffic lights were installed. Electric trolleys (at 12 miles per hour) became the main transportation service for middle class shoppers and office workers until they bought automobiles after 1945 and commuted from more distant suburbs in privacy and comfort on asphalt highways.[66]

See also: Bitumount and History of the petroleum industry in Canada (oil sands and heavy oil)

Canada has the world's largest deposit of natural bitumen in the Athabasca oil sands, and Canadian First Nations along the Athabasca River had long used it to waterproof their canoes. In 1719, a Cree named Wa-Pa-Su brought a sample for trade to Henry Kelsey of the Hudson’s Bay Company, who was the first recorded European to see it. However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."[21]

The value of the deposit was obvious from the start, but the means of extracting the bitumen was not. The nearest town, Fort McMurray, Alberta, was a small fur trading post, other markets were far away, and transportation costs were too high to ship the raw bituminous sand for paving. In 1915, Sidney Ells of the Federal Mines Branch experimented with separation techniques and used the product to pave 600 feet of road in Edmonton, Alberta. Other roads in Alberta were paved with material extracted from oil sands, but it was generally not economic. During the 1920s Dr. Karl A. Clark of the Alberta Research Council patented a hot water oil separation process and entrepreneur Robert C. Fitzsimmons[67] built the Bitumount oil separation plant, which between 1925 and 1958 produced up to 300 barrels (50 m3) per day of bitumen using Dr. Clark's method. Most of the bitumen was used for waterproofing roofs, but other uses included fuels, lubrication oils, printers ink, medicines, rust- and acid-proof paints, fireproof roofing, street paving, patent leather, and fence post preservatives.[21] Eventually Fitzsimmons ran out of money and the plant was taken over by the Alberta government. Today the Bitumount plant is a Provincial Historic Site.[68]

Bitumen was used in early photographic technology. In 1826 or 1827, it was used by French scientist Joseph Nicéphore Niépce to make the oldest surviving photograph from nature. The bitumen was thinly coated onto a pewter plate which was then exposed in a camera. Exposure to light hardened the bitumen and made it insoluble, so that when it was subsequently rinsed with a solvent only the sufficiently light-struck areas remained. Many hours of exposure in the camera were required, making bitumen impractical for ordinary photography, but from the 1850s to the 1920s it was in common use as a photoresist in the production of printing plates for various photomechanical printing processes.[69][70]

Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle.[71]

The vast majority of refined asphalt is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use, asphalt is produced to specification. This is achieved either by refining or blending. It is estimated that the current world use of asphalt is approximately 102 million tonnes per year. Approximately 85% of all the asphalt produced is used as the binder in asphalt concrete for roads. It is also used in other paved areas such as airport runways, car parks and footways. Typically, the production of asphalt concrete involves mixing fine and coarse aggregates such as sand, gravel and crushed rock with asphalt, which acts as the binding agent. Other materials, such as recycled polymers (e.g., rubber tyres), may be added to the asphalt to modify its properties according to the application for which the asphalt is ultimately intended.

A further 10% of global asphalt production is used in roofing applications, where its waterproofing qualities are invaluable. The remaining 5% of asphalt is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet tile backing and paint. Asphalt is applied in the construction and maintenance of many structures, systems, and components, such as the following:

Main article: Asphalt concrete

The largest use of asphalt is for making asphalt concrete for road surfaces; this accounts for approximately 85% of the asphalt consumed in the United States. Asphalt concrete pavement mixes are typically composed of 5% asphalt cement and 95% aggregates (stone, sand, and gravel). Due to its highly viscous nature, asphalt cement must be heated so it can be mixed with the aggregates at the asphalt mixing facility. The temperature required varies depending upon characteristics of the asphalt and the aggregates, but warm-mix asphalt technologies allow producers to reduce the temperature required. There are about 4,000 asphalt concrete mixing plants in the US, and a similar number in Europe.[72]

When maintenance is performed on asphalt pavements, such as milling to remove a worn or damaged surface, the removed material can be returned to a facility for processing into new pavement mixtures. The asphalt in the removed material can be reactivated and put back to use in new pavement mixes.[73] With some 95% of paved roads being constructed of or surfaced with asphalt,[74] a substantial amount of asphalt pavement material is reclaimed each year. According to industry surveys conducted annually by the Federal Highway Administration and the National Asphalt Pavement Association, more than 99% of the asphalt removed each year from road surfaces during widening and resurfacing projects is reused as part of new pavements, roadbeds, shoulders and embankments.[75]

Asphalt concrete paving is widely used in airports around the world. Due to the sturdiness and ability to be repaired quickly, it is widely used for runways.

Further information: Fibre mastic asphalt

Mastic asphalt is a type of asphalt that differs from dense graded asphalt (asphalt concrete) in that it has a higher asphalt (binder) content, usually around 7–10% of the whole aggregate mix, as opposed to rolled asphalt concrete, which has only around 5% asphalt. This thermoplastic substance is widely used in the building industry for waterproofing flat roofs and tanking underground. Mastic asphalt is heated to a temperature of 210 °C (410 °F) and is spread in layers to form an impervious barrier about 20 millimeters (0.8 inches) thick.

A number of technologies allow asphalt to be mixed at much lower temperatures. These involve mixing with petroleum solvents to form "cutbacks" with reduced melting point or mixing with water to turn the asphalt into an emulsion. Asphalt emulsions contain up to 70% asphalt and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock, gravel or crushed slag. Slurry seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on the surface of a road. Cold-mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth, and asphalt emulsions are also blended into recycled hot-mix asphalt to create low-cost pavements.

Main article: Synthetic crude oil See also: Petroleum production in Canada

Synthetic crude oil, also known as syncrude, is the output from a bitumen upgrader facility used in connection with oil sand production in Canada. Bituminous sands are mined using enormous (100 ton capacity) power shovels and loaded into even larger (400 ton capacity) dump trucks for movement to an upgrading facility. The process used to extract the bitumen from the sand is a hot water process originally developed by Dr. Karl Clark of the University of Alberta during the 1920s. After extraction from the sand, the bitumen is fed into a bitumen upgrader which converts it into a light crude oil equivalent. This synthetic substance is fluid enough to be transferred through conventional oil pipelines and can be fed into conventional oil refineries without any further treatment. By 2015 Canadian bitumen upgraders were producing over 1 million barrels (160×10^3 m3) per day of synthetic crude oil, of which 75% was exported to oil refineries in the United States.[76]

In Alberta, five bitumen upgraders produce synthetic crude oil and a variety of other products: The Suncor Energy upgrader near Fort McMurray, Alberta produces synthetic crude oil plus diesel fuel; the Syncrude Canada, Canadian Natural Resources, and Nexen upgraders near Fort McMurray produce synthetic crude oil; and the Shell Scotford Upgrader near Edmonton produces synthetic crude oil plus an intermediate feedstock for the nearby Shell Oil Refinery.[77] A sixth upgrader, under construction in 2015 near Redwater, Alberta, will upgrade half of its crude bitumen directly to diesel fuel, with the remainder of the output being sold as feedstock to nearby oil refineries and petrochemical plants.[78]

See also: Western Canadian Select

Canadian bitumen does not differ substantially from oils such as Venezuelan extra-heavy and Mexican heavy oil in chemical composition, and the real difficulty is moving the extremely viscous bitumen through oil pipelines to the refinery. Many modern oil refineries are extremely sophisticated and can process non-upgraded bitumen directly into products such as gasoline, diesel fuel, and refined asphalt without any preprocessing. This is particularly common in areas such as the US Gulf coast, where refineries were designed to process Venezuelan and Mexican oil, and in areas such as the US Midwest where refineries were rebuilt to process heavy oil as domestic light oil production declined. Given the choice, such heavy oil refineries usually prefer to buy bitumen rather than synthetic oil because the cost is lower, and in some cases because they prefer to produce more diesel fuel and less gasoline.[77] By 2015 Canadian production and exports of non-upgraded bitumen exceeded that of synthetic crude oil at over 1.3 million barrels (210×10^3 m3) per day, of which about 65% was exported to the United States.[76]

Because of the difficulty of moving crude bitumen through pipelines, non-upgraded bitumen is usually diluted with natural-gas condensate in a form called dilbit or with synthetic crude oil, called synbit. However, to meet international competition, much non-upgraded bitumen is now sold as a blend of multiple grades of bitumen, conventional crude oil, synthetic crude oil, and condensate in a standardized benchmark product such as Western Canadian Select. This sour, heavy crude oil blend is designed to have uniform refining characteristics to compete with internationally marketed heavy oils such as Mexican Mayan or Arabian Dubai Crude.[77]

Asphalt was used starting in the 1960s as an hydrophobic matrix aiming to encapsulate radioactive waste such as medium-activity salts (mainly soluble sodium nitrate and sodium sulfate) produced by the reprocessing of spent nuclear fuels or radioactive sludges from sedimentation ponds.[79][80] Bituminised radioactive waste containing highly radiotoxic alpha-emitting transuranic elements from nuclear reprocessing plants have been produced at industrial scale in France, Belgium and Japan, but this type of waste conditioning has been abandoned because operational safety issues (risks of fire, as occurred in a bituminisation plant at Tokai Works in Japan)[81][82] and long-term stability problems related to their geological disposal in deep rock formations. One of the main problem is the swelling of asphalt exposed to radiation and to water. Asphalt swelling is first induced by radiation because of the presence of hydrogen gas bubbles generated by alpha and gamma radiolysis.[83][84] A second mechanism is the matrix swelling when the encapsulated hygroscopic salts exposed to water or moisture start to rehydrate and to dissolve. The high concentration of salt in the pore solution inside the bituminised matrix is then responsible for osmotic effects inside the bituminised matrix. The water moves in the direction of the concentrated salts, the asphalt acting as a semi-permeable membrane. This also causes the matrix to swell. The swelling pressure due to osmotic effect under constant volume can be as high as 200 bar. If not properly managed, this high pressure can cause fractures in the near field of a disposal gallery of bituminised medium-level waste. When the bituminised matrix has been altered by swelling, encapsulated radionuclides are easily leached by the contact of ground water and released in the geosphere. The high ionic strength of the concentrated saline solution also favours the migration of radionuclides in clay host rocks. The presence of chemically reactive nitrate can also affect the redox conditions prevailing in the host rock by establishing oxidizing conditions, preventing the reduction of redox-sensitive radionuclides. Under their higher valences, radionuclides of elements such as selenium, technetium, uranium, neptunium and plutonium have a higher solubility and are also often present in water as non-retarded anions. This makes the disposal of medium-level bituminised waste very challenging.

Different type of asphalt have been used: blown bitumen (partly oxidized with air oxygen at high temperature after distillation, and harder) and direct distillation bitumen (softer). Blown bitumens like Mexphalte, with a high content of saturated hydrocarbons, are more easily biodegraded by microorganisms than direct distillation bitumen, with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons.[85]

Concrete encapsulation of radwaste is presently considered a safer alternative by the nuclear industry and the waste management organisations.

Roofing shingles account for most of the remaining asphalt consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Asphalt is used to make Japan black, a lacquer known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker.[86] Asphalt is also used to seal some alkaline batteries during the manufacturing process.

Typical asphalt plant for making asphalt

About 40,000,000 tons were produced in 1984.[needs update] It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as naphtha, gasoline and diesel). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude asphalt is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This step makes the product harder and more viscous.[5]

Asphalt is typically stored and transported at temperatures around 150 °C (302 °F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.

Main article: Oil sands

Naturally occurring crude bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from "oil sands", currently under development in Alberta, Canada. Canada has most of the world's supply of natural bitumen, covering 140,000 square kilometres[14] (an area larger than England), giving it the second-largest proven oil reserves in the world. The Athabasca oil sands are the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods. Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020.[15] The total amount of crude bitumen in Alberta that could be extracted is estimated to be about 310 billion barrels (50×10^9 m3),[8] which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.

Main articles: Peak oil, Global warming, and Bioasphalt

Although uncompetitive economically, asphalt can be made from nonpetroleum-based renewable resources such as sugar, molasses and rice, corn and potato starches. Asphalt can also be made from waste material by fractional distillation of used motor oil, which is sometimes otherwise disposed of by burning or dumping into landfills. Use of motor oil may cause premature cracking in colder climates, resulting in roads that need to be repaved more frequently.[87]

Nonpetroleum-based asphalt binders can be made light-colored. Lighter-colored roads absorb less heat from solar radiation, reducing their contribution to the urban heat island effect.[88] Parking lots that use asphalt alternatives are called green parking lots.

Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania, the only European asphalt mine still in use. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring and ball) around 120 °C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.

Albanian bitumen extraction has a long history and was practiced in an organized way by the Romans. After centuries of silence, the first mentions of Albanian bitumen appeared only in 1868, when the Frenchman Coquand published the first geological description of the deposits of Albanian bitumen. In 1875, the exploitation rights were granted to the Ottoman government and in 1912, they were transferred to the Italian company Simsa. Since 1945, the mine was exploited by the Albanian government and from 2001 to date, the management passed to a French company, which organized the mining process for the manufacture of the natural bitumen on an industrial scale.[89]

Today the mine is predominantly exploited in an open pit quarry but several of the many underground mines (deep and extending over several km) still remain viable. Selenizza is produced primarily in granular form, after melting the bitumen pieces selected in the mine.

Selenizza[90] is mainly used as an additive in the road construction sector. It is mixed with traditional asphalt to improve both the viscoelastic properties and the resistance to ageing. It may be blended with the hot asphalt in tanks, but its granular form allows it to be fed in the mixer or in the recycling ring of normal asphalt plants. Other typical applications include the production of mastic asphalts for sidewalks, bridges, car-parks and urban roads as well as drilling fluid additives for the oil and gas industry. Selenizza is available in powder or in granular material of various particle sizes and is packaged in sacks or in thermal fusible polyethylene bags.

A life-cycle assessment study of the natural selenizza compared with petroleum asphalt has shown that the environmental impact of the selenizza is about half the impact of the road asphalt produced in oil refineries in terms of carbon dioxide emission.[91]

People can be exposed to asphalt in the workplace by breathing in fumes or skin absorption. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit of 5 mg/m3 over a 15-minute period.[92]

Asphalt is basically an inert material that must be heated or diluted to a point where it becomes workable for the production of materials for paving, roofing, and other applications. In examining the potential health hazards associated with asphalt, the International Agency for Research on Cancer (IARC) determined that it is the application parameters, predominantly temperature, that affect occupational exposure and the potential bioavailable carcinogenic hazard/risk of the asphalt emissions.[93] In particular, temperatures greater than 199 °C (390 °F), were shown to produce a greater exposure risk than when asphalt was heated to lower temperatures, such as those typically used in asphalt pavement mix production and placement.[94] IARC has classified asphalt as a Class 2B possible carcinogen.

An asphalt mixing plant for hot aggregate
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  54. ^ "Registration of Clarmac Roads", The Law Reports: Chancery Division, Vol. 1: 544–547, 1921, retrieved 17 June 2010 
  55. ^ "Clarmac and Clarphalte", The Building News and Engineering Journal, Vol. 109: July to December 1915 (No. 3157): 2–4 (n13–15 in electronic page field), 7 July 1915, retrieved 18 June 2010 
  56. ^ Roads laid with Clarmac The Building News and Engineering Journal, 1915 109 (3157), p.3 (n14 in electronic field).
  57. ^ a b Clarmac financial difficults due to WW1 Debentures deposited The Law Reports: Chancery Division, (1921) Vol. 1 p.545. Retrieved 17 June 2010.
  58. ^ "Notice of the Winding up of Clarmac Roads", The London Gazette (29340): 10568, 26 October 1915, retrieved 15 June 2010 
  59. ^ a b Claridge's Patent Asphalte Co. compulsorily wound up Funds invested in new company The Law Times Reports (1921) Vol.125, p.256. Retrieved 15 June 2010.
  60. ^ "Claridge's Patent Asphalte Co. winds up 10 November 1917". The London Gazette. 16 November 1917. p. 11863. 
  61. ^ Hobhouse, Hermione (General Editor) (1994). "British History Online". 'Cubitt Town: Riverside area: from Newcastle Drawdock to Cubitt Town Pier', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs. pp. 528–532 (see text at refs 507 & 510). Retrieved 8 November 2009. 
  62. ^ Stockton, Nick (23 June 2017). "Plastic Water Bottles Might Have Poisoned Ancient Californians". Wired. Retrieved 26 June 2017. 
  63. ^ McNichol, Dan (2005). Paving the Way: Asphalt in America. Lanham, MD: National Asphalt Pavement Association. ISBN 0-914313-04-5. Archived from the original on 2006-08-29. 
  64. ^ David O. Whitten, "A Century of Parquet Pavements: Wood as a Paving Material In The United States And Abroad, 1840-1940." Essays in Economic and Business History 15 (1997): 209-26.
  65. ^ Arthur Maier Schlesinger, The Rise of the City: 1878-1898 (1933) p 88-93.
  66. ^ John D. Fairfield, "Rapid Transit: Automobility and Settlement in Urban America" Reviews in American History 23#1 (1995), pp. 80-85 online.
  67. ^ "Robert C. Fitzsimmons (1881–1971)". Canadian Petroleum Hall of Fame. 2010. Retrieved 2016-01-20. 
  68. ^ "Bitumount". Government of Alberta. 2016. Retrieved 2016-01-20. 
  69. ^ Niépce Museum history pages. Retrieved 27 October 2012. Archived 3 August 2007 at the Wayback Machine.
  70. ^ The First Photograph (Harry Ransom Center, University of Texas at Austin). Retrieved 27 October 2012.
  71. ^ Spiegelman, Willard (2009-08-21). "Revolutionary Romanticism: 'The Raft of the Medusa' brought energy to French art". The Wall Street Journal. New York City. Retrieved 2016-01-27. 
  72. ^ The Asphalt Paving Industry: A Global Perspective, 2nd Edition (PDF). Lanham, Maryland, and Brussels: National Asphalt Pavement Association and European Asphalt Pavement Association. February 2011. ISBN 0-914313-06-1. Retrieved 27 September 2012. 
  73. ^ "How Should We Express RAP and RAS Contents?". Asphalt Technology E-News. 26 (2). 2014. Archived from the original on 9 June 2015. Retrieved 2015-08-13. 
  74. ^ "Highway Statistics Series: Public Road Length Miles by Type of Surface and Ownership". Federal Highway Administration. 2013-10-01. Retrieved 2015-08-13. 
  75. ^ "Asphalt Pavement Recycling". Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2009–2013. National Asphalt Pavement Association. Retrieved 13 August 2015. 
  76. ^ a b "Crude Oil and Petroleum Products". National Energy Board of Canada. Retrieved January 21, 2016. 
  77. ^ a b c "2015 CAPP Crude Oil Forecast, Markets & Transportation". Canadian Association of Petroleum Producers. Archived from the original on 20 January 2016. Retrieved January 21, 2016. 
  78. ^ "The Project". North West Redwater Partnership. Retrieved January 21, 2016. 
  79. ^ Rodier, J., Scheidhauer, J., & Malabre, M. (1961). The conditioning of radioactive waste by bitumen (No. CEA-R—1992). CEA Marcoule.
  80. ^ Lefillatre, G., Rodier, J., Hullo, R., Cudel, Y., & Rodi, L. (1969). Use of a thin-film evaporator for bitumen coating of radioactive concentrates (No. CEA-R—3742). CEA Marcoule.
  81. ^ Sato, Y., Miura, A., Kato, Y., Suzuki, H., Shigetome, Y., Koyama, T., ... & Yamanouchi, T. (2000). Study on the cause of the fire and explosion incident at Bituminization Demonstration Facility of PNC Tokai Works. In Nuclear waste: from research to industrial maturity. International conference (pp. 179–190).
  82. ^ Okada, K., Nur, R. M., & Fujii, Y. (1999). The formation of explosive compounds in bitumen/nitrate mixtures. Journal of hazardous materials, 69(3), 245–256.
  83. ^ Johnson, D.I., Hitchon, J.W., & Phillips, D.C. (1986). Further observations of the swelling of bitumens and simulated bitumen wasteforms during γ-irradiation (No. AERE-R—12292). UKAEA Harwell Lab. Materials Development Division.
  84. ^ Phillips, D. C., Hitchon, J. W., Johnson, D. I., & Matthews, J. R. (1984). The radiation swelling of bitumens and bitumenised wastes. Journal of nuclear materials, 125(2), 202–218.
  85. ^ Ait-Langomazino, N., Sellier, R., Jouquet, G., & Trescinski, M. (1991). Microbial degradation of bitumen. Experientia, 47(6), 533–539.
  86. ^ Mohd, Meraj Jafri; Singh, D. K. (march 2013). "Cashew Nutshell Liquid Resin" (PDF). IJRREST: International Journal of Research Review in Engineering Science and Technology. 2: 60–65.  Check date values in: |date= (help)
  87. ^ Hesp, Simon A.M.; Herbert F. Shurvell (2010). "X-ray fluorescence detection of waste engine oil residue in asphalt and its effect on cracking in service". International Journal of Pavement Engineering. 11 (6): 541–553. doi:10.1080/10298436.2010.488729. ISSN 1029-8436. Retrieved 2014-03-24. 
  88. ^ Heat Island Effect. From the website of the US Environmental Protection Agency.
  89. ^ Giavarini, Carlo (March 2013). Six Thousand Years of Asphalt. SITEB. pp. 71–78. ISBN 978-88-908408-3-8. 
  90. ^ [3], Selenice Bitumi for more information about Selenizza
  91. ^ Giavarini, C.; Pellegrini, A. "Life cycle assessment of Selenice asphalt compared with petroleum bitumen". The 1st Albanian Congress on Roads: 234–237. 
  92. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Asphalt fumes". www.cdc.gov. Retrieved 2015-11-27. 
  93. ^ IARC (2013). Bitumens and Bitumen Emissions, and Some N- and S-Heterocyclic Polycyclic Aromatic Hydrocarbons. 103. Lyon, France: International Agency for Research on Cancer. ISBN 978-92-832-1326-0. Retrieved 2015-12-07. 
  94. ^ Cavallari, J. M.; Zwack, L. M.; Lange, C. R.; Herrick, R. F.; Mcclean, M. D. (2012). "Temperature-Dependent Emission Concentrations of Polycyclic Aromatic Hydrocarbons in Paving and Built-Up Roofing Asphalts". Annals of Occupational Hygiene. 56 (2): 148–160. doi:10.1093/annhyg/mer107 . ISSN 0003-4878. 
  95. ^ "Contacto – Eco Roofing". epdmecoroofing.com. 
  96. ^ "Follow the evolution of the road from path to pavement". 


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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Asphalt Parking Lot in Parkhurst except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Asphalt Cost For Driveway is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Asphalt Parking Lot Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Asphalt Driveway Paving Near Me the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Asphalt

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

Asphalt concrete

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

Michigan left

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

Macadam

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Paver Repair Quotes Raised sidewalks beside a 2000-year-old paved road, Pompeii, Italy

A sidewalk (American English) or pavement (British English), also known as a footpath or footway, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade (height) and is normally separated from the vehicular section by a curb. There may also be a median strip or road verge (a strip of vegetation, grass or bushes or trees or a combination of these) either between the sidewalk and the roadway or between the sidewalk and the boundary.

In some places, the same term may also be used for a paved path, trail or footpath that is not next to a road, for example, a path through a park.

The term "sidewalk" is usually preferred in most of North America, along with many other countries worldwide that are not members of the Commonwealth of Nations. The term "pavement" is more common in the United Kingdom,[1] as well as parts of the Mid-Atlantic United States such as Philadelphia and New Jersey.[2][3] Many Commonwealth countries use the term "footpath". The professional, civil engineering and legal term for this in North America is "sidewalk" while in the United Kingdom it is "footway".[4]

In the United States, the term sidewalk is used for the pedestrian path beside a road. "Shared use paths" or "multi-use paths" are available for use by both pedestrians and bicyclists.[5] "Walkway" is a more comprehensive term that includes stairs, ramps, passageways, and related structures that facilitate the use of a path as well as the sidewalk.[6]

In the UK, the term "footpath" is mostly used for paths that do not abut a roadway.[7] The term "shared-use path" is used where cyclists are also able to use the same section of path as pedestrians.[8]

East India House, Leadenhall Street, London, 1766. The sidewalk is separated from the main street by six bollards in front of the building.

There is evidence that sidewalks were built in ancient times. It was claimed that the Greek city of Corinth was paved by the 4th-century, and the Romans were particularly prolific sidewalk builders – they called them semitas.[9]

However, by the Middle Ages, narrow roads had reverted to being simultaneously used by pedestrians and wagons without any formal separation between the two categories. Early attempts at ensuring the adequate maintenance of foot-ways or sidewalks were often made, such as the 1623 Act for Colchester, although they were generally not very effective.[10]

Following the Great Fire of London in 1666, attempts were slowly made to bring some order to the sprawling city. In 1671, 'Certain Orders, Rules and Directions Touching the Paving and Cleansing The Streets, Lanes and Common Passages within the City of London' were formulated, calling for all streets to be adequately paved for pedestrians with cobblestones. Purbeck stone was widely used as a durable paving material. Bollards were also installed to protect pedestrians from the traffic in the middle of the road.

A series of Paving Acts from the House of Commons during the 18th century, especially the 1766 Paving & Lighting Act, authorized the City of London Corporation to create foot-ways throughout all the streets of London, to pave them with Purbeck stone (the thoroughfare in the middle was generally cobblestone) and to raise them above the street level with curbs forming the separation.[11] The Corporation was also made responsible for the regular upkeep of the roads, including their cleaning and repair, for which they charged a tax from 1766.[12] By the late 19th-century large and spacious sidewalks were routinely constructed in European capitals, and were associated with urban sophistication.

In the United States, adjoining property owners must in most situations finance all or part of the cost of sidewalk construction. In a legal case in 1917 involving E. L. Stewart, a former member of the Louisiana House of Representatives and a lawyer in Minden in Webster Parish, the Louisiana Supreme Court ruled that owners must pay whether they wish for the sidewalk to be constructed or not.[13]

Pedestrians walking on the pavement (sidewalk) in London.

Sidewalks play an important role in transportation, as they provide a safe path for people to walk along that is separated from the motorized traffic. They aid road safety by minimizing interaction between pedestrians and motorized traffic. Sidewalks are normally in pairs, one on each side of the road, with the center section of the road for motorized vehicles.

In rural roads, sidewalks may not be present as the amount of traffic (pedestrian or motorized) may not be enough to justify separating the two. In suburban and urban areas, sidewalks are more common. In town and city centers (known as downtown in North America) the amount of pedestrian traffic can exceed motorized traffic, and in this case the sidewalks can occupy more than half of the width of the road, or the whole road can be reserved for pedestrians, see Pedestrian zone.

Sidewalks may have a small effect on reducing vehicle miles traveled and carbon dioxide emissions. A study of sidewalk and transit investments in Seattle neighborhoods found vehicle travel reductions of 6 to 8% and CO2 emission reductions of 1.3 to 2.2% [14]

Sidewalk with bike path See also: Road traffic safety

Research commissioned for the Florida Department of Transportation, published in 2005, found that, in Florida, the Crash Reduction Factor (used to estimate the expected reduction of crashes during a given period) resulting from the installation of sidewalks averaged 74%.[15] Research at the University of North Carolina for the U.S. Department of Transportation found that the presence or absence of a sidewalk and the speed limit are significant factors in the likelihood of a vehicle/pedestrian crash. Sidewalk presence had a risk ratio of 0.118, which means that the likelihood of a crash on a road with a paved sidewalk was 88.2 percent lower than one without a sidewalk. “This should not be interpreted to mean that installing sidewalks would necessarily reduce the likelihood of pedestrian/motor vehicle crashes by 88.2 percent in all situations. However, the presence of a sidewalk clearly has a strong beneficial effect of reducing the risk of a ‘walking along roadway’ pedestrian/motor vehicle crash.” The study does not count crashes that happen when walking across a roadway. The speed limit risk ratio was 1.116, which means that a 16.1-km/h (10-mi/h) increase in the limit yields a factor of (1.116)10 or 3.[16]

The presence or absence of sidewalks was one of three factors that were found to encourage drivers to choose lower, safer speeds.[17]

On the other hand, the implementation of schemes which involve the removal of sidewalks, such as shared space schemes, are reported to deliver a dramatic drop in crashes and congestion too, which indicates that a number of other factors, such as the local speed environment, also play an important role in whether sidewalks are necessarily the best local solution for pedestrian safety.[18]

In cold weather, black ice is a common problem with unsalted sidewalks. The ice forms a thin transparent surface film which is almost impossible to see, and so results in many slips by pedestrians.

Riding bicycles on sidewalks is discouraged since some research shows it to be more dangerous than riding in the street.[19] Some jurisdictions prohibit sidewalk riding except for children. In addition to the risk of cyclist/pedestrian collisions, cyclists face increase risks from collisions with motor vehicles at street crossings and driveways. Riding in the direction opposite to traffic in the adjacent lane is especially risky.[20]

Since residents of neighborhoods with sidewalks are more likely to walk, they tend to have lower rates of cardiovascular disease, obesity, and other health issues related to sedentary lifestyles.[21] Also, children who walk to school have been shown to have better concentration.[22]

Native Americans busking at Orchard Road, Singapore

Some sidewalks may be used as social spaces with sidewalk cafes, markets, or busking musicians, as well as for parking for a variety of vehicles including cars, motorbikes and bicycles.

Contemporary sidewalks are most often made of concrete in the United States and Canada, while tarmac, asphalt, brick, stone, slab and (increasingly) rubber are more common in Europe.[23] Different materials are more or less friendly environmentally: pumice-based trass, for example, when used as an extender is less energy-intensive than Portland cement concrete or petroleum-based materials such as asphalt or tar-penetration macadam). Multi-use paths alongside roads are sometimes made of materials that are softer than concrete, such as asphalt.

In the 19th century and early 20th century, sidewalks of wood were common in some North American locations. They may still be found at historic beach locations and in conservation areas to protect the land beneath and around, called boardwalks.

Brick sidewalks are found in some urban areas, usually for aesthetic purposes. Brick sidewalk construction usually involves the usage of a mechanical vibrator to lock the bricks in place after they have been laid (and/or to prepare the soil before laying). Although this might also be done by other tools (as regular hammers and heavy rolls), a vibrator is often used to speed up the process.

Stone slabs called flagstones or flags are sometimes used where an attractive appearance is required, as in historic town centers. In other places, pre-cast concrete slabs (called paving slabs or, less correctly, paving stones) are used. These may be colored or textured to resemble stone.

Freshly laid concrete sidewalk, with horizontal strain-relief grooves faintly visible

In the United States and Canada, the most common type of sidewalk consists of a poured concrete ribbon, examples of which from as early as the 1860s can be found in good repair in San Francisco, and stamped with the name of the contractor and date of installation.[citation needed] When quantities of Portland cement were first imported to the United States in the 1880s, its principal use was in the construction of sidewalks.[24]

Today, most sidewalk ribbons are constructed with cross-lying strain-relief grooves placed or sawn at regular intervals typically 5 feet (1.5 m) apart. This partitioning, an improvement over the continuous slab, was patented in 1924 by Arthur Wesley Hall and William Alexander McVay, who wished to minimize damage to the concrete from the effects of tectonic and temperature fluctuations, both of which can crack longer segments.[25] The technique is not perfect, as freeze-thaw cycles (in cold-weather regions) and tree root growth can eventually result in damage which requires repair.

In highly variable climates which undergo multiple freeze-thaw cycles, the concrete blocks will be separated by expansion joints to allow for thermal expansion without breakage. The use of expansion joints in sidewalks may not be necessary, as the concrete will shrink while setting.[26]

In the United Kingdom, Australia and France suburban sidewalks are most commonly constructed of tarmac. In urban or inner-city areas sidewalks are most commonly constructed of slabs, stone, or brick depending upon the surrounding street architecture and furniture.

Road surface

Asphalt Surfacing Company Price Asphalt batch mix plant A machine laying asphalt concrete, fed from a dump truck

Asphalt concrete (commonly called asphalt,[1] blacktop, or pavement in North America, and tarmac or bitumen macadam or rolled asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, as well as the core of embankment dams.[2] It consists of mineral aggregate bound together with asphalt, laid in layers, and compacted. The process was refined and enhanced by Belgian inventor and U.S. immigrant Edward de Smedt.[3]

The terms asphalt (or asphaltic) concrete, bituminous asphalt concrete, and bituminous mixture are typically used only in engineering and construction documents, which define concrete as any composite material composed of mineral aggregate adhered with a binder. The abbreviation, AC, is sometimes used for asphalt concrete but can also denote asphalt content or asphalt cement, referring to the liquid asphalt portion of the composite material.

As shown in this cross-section, many older roadways are smoothed by applying a thin layer of asphalt concrete to the existing portland cement concrete, creating a composite pavement.

Mixing of asphalt and aggregate is accomplished in one of several ways:[4]

Hot-mix asphalt concrete (commonly abbreviated as HMA) This is produced by heating the asphalt binder to decrease its viscosity, and drying the aggregate to remove moisture from it prior to mixing. Mixing is generally performed with the aggregate at about 300 °F (roughly 150 °C) for virgin asphalt and 330 °F (166 °C) for polymer modified asphalt, and the asphalt cement at 200 °F (95 °C). Paving and compaction must be performed while the asphalt is sufficiently hot. In many countries paving is restricted to summer months because in winter the compacted base will cool the asphalt too much before it is able to be packed to the required density. HMA is the form of asphalt concrete most commonly used on high traffic pavements such as those on major highways, racetracks and airfields. It is also used as an environmental liner for landfills, reservoirs, and fish hatchery ponds.[5] Asphaltic concrete laying machine in operation in Laredo, Texas Warm-mix asphalt concrete (commonly abbreviated as WMA) This is produced by adding either zeolites, waxes, asphalt emulsions, or sometimes even water to the asphalt binder prior to mixing. This allows significantly lower mixing and laying temperatures and results in lower consumption of fossil fuels, thus releasing less carbon dioxide, aerosols and vapors. Not only are working conditions improved, but the lower laying-temperature also leads to more rapid availability of the surface for use, which is important for construction sites with critical time schedules. The usage of these additives in hot mixed asphalt (above) may afford easier compaction and allow cold weather paving or longer hauls. Use of warm mix is rapidly expanding. A survey of US asphalt producers found that nearly 25% of asphalt produced in 2012 was warm mix, a 416% increase since 2009.[6] Cold-mix asphalt concrete This is produced by emulsifying the asphalt in water with (essentially) soap prior to mixing with the aggregate. While in its emulsified state the asphalt is less viscous and the mixture is easy to work and compact. The emulsion will break after enough water evaporates and the cold mix will, ideally, take on the properties of an HMA pavement. Cold mix is commonly used as a patching material and on lesser trafficked service roads. Cut-back asphalt concrete Is a form of cold mix asphalt produced by dissolving the binder in kerosene or another lighter fraction of petroleum prior to mixing with the aggregate. While in its dissolved state the asphalt is less viscous and the mix is easy to work and compact. After the mix is laid down the lighter fraction evaporates. Because of concerns with pollution from the volatile organic compounds in the lighter fraction, cut-back asphalt has been largely replaced by asphalt emulsion.[7] Mastic asphalt concrete, or sheet asphalt This is produced by heating hard grade blown bitumen (i.e., partly oxidised) in a green cooker (mixer) until it has become a viscous liquid after which the aggregate mix is then added. The bitumen aggregate mixture is cooked (matured) for around 6–8 hours and once it is ready the mastic asphalt mixer is transported to the work site where experienced layers empty the mixer and either machine or hand lay the mastic asphalt contents on to the road. Mastic asphalt concrete is generally laid to a thickness of around ​3⁄4–1 ​3⁄16 inches (20–30 mm) for footpath and road applications and around ​3⁄8 of an inch (10 mm) for flooring or roof applications. High-modulus asphalt concrete, sometimes referred to by the French-language acronym EMÉ (enrobé à module élevé) This uses a very hard bituminous (penetration 10/20), sometimes modified, in proportions close to 6% on the weight of the aggregates, and a proportion of mineral powder also high, between 8–10%, to create an asphalt concrete layer with a high modulus of elasticity, of the order of 13000 MPa, as well as very high fatigue strengths.[8] High-modulus asphalt layers are used both in reinforcement operations and in the construction of new reinforcements for medium and heavy traffic. In base layers, they tend to exhibit a greater capacity of absorbing tensions and, in general, better fatigue resistance.[9]

In addition to the asphalt and aggregate, additives, such as polymers, and antistripping agents may be added to improve the properties of the final product.

Asphalt concrete pavements—especially those at airfields—are sometimes called tarmac for historical reasons, although they do not contain tar and are not constructed using the macadam process.

A variety of specialty asphalt concrete mixtures have been developed to meet specific needs, such as stone-matrix asphalt, which is designed to ensure a very strong wearing surface, or porous asphalt pavements, which are permeable and allow water to drain through the pavement for controlling stormwater.

An airport taxiway, one of the uses of asphalt concrete

Different types of asphalt concrete have different performance characteristics in terms of surface durability, tire wear, braking efficiency and roadway noise. In principle, the determination of appropriate asphalt performance characteristics must take into account the volume of traffic in each vehicle category, and the performance requirements of the friction course. Asphalt concrete generates less roadway noise than a Portland cement concrete surface, and is typically less noisy than chip seal surfaces.[10][11]

Because tire noise is generated through the conversion of kinetic energy to sound waves, more noise is produced as the speed of a vehicle increases. The notion that highway design might take into account acoustical engineering considerations, including the selection of the type of surface paving, arose in the early 1970s.[12][13] With regard to structural performance, the asphalt behaviour depends on a variety of factors including the material, loading and environmental condition. Furthermore, the performance of pavement varies over time. Therefore, the long-term behaviour of asphalt pavement is different from its short-term performance. The LTPP is a research program by the FHWA, which is specifically focusing on long-term pavement behaviour.[14][15]

Asphalt damaged by frost heaves

Asphalt deterioration can include crocodile cracking, potholes, upheaval, raveling, bleeding, rutting, shoving, stripping, and grade depressions. In cold climates, frost heaves can crack asphalt even in one winter. Filling the cracks with bitumen is a temporary fix, but only proper compaction and drainage can slow this process.

Factors that cause asphalt concrete to deteriorate over time mostly fall into one of three categories: construction quality, environmental considerations, and traffic loads. Often, damage results from combinations of factors in all three categories.

Construction quality is critical to pavement performance. This includes the construction of utility trenches and appurtenances that are placed in the pavement after construction. Lack of compaction in the surface of the asphalt, especially on the longitudinal joint can reduce the life of a pavement by 30 to 40%. Service trenches in pavements after construction have been said to reduce the life of the pavement by 50%, mainly due to the lack of compaction in the trench, and also because of water intrusion through improperly sealed joints.

Environmental factors include heat and cold, the presence of water in the subbase or subgrade soil underlying the pavement, and frost heaves.

High temperatures soften the asphalt binder, allowing heavy tire loads to deform the pavement into ruts. Paradoxically, high heat and strong sunlight also cause the asphalt to oxidize, becoming stiffer and less resilient, leading to crack formation. Cold temperatures can cause cracks as the asphalt contracts. Cold asphalt is also less resilient and more vulnerable to cracking.

Water trapped under the pavement softens the subbase and subgrade, making the road more vulnerable to traffic loads. Water under the road freezes and expands in cold weather, causing and enlarging cracks. In spring thaw, the ground thaws from the top down, so water is trapped between the pavement above and the still-frozen soil underneath. This layer of saturated soil provides little support for the road above, leading to the formation of potholes. This is more of a problem for silty or clay soils than sandy or gravelly soils. Some jurisdictions pass frost laws to reduce the allowable weight of trucks during the spring thaw season and protect their roads.

The damage a vehicle causes is proportional to the axle load raised to the fourth power,[16] so doubling the weight an axle carries actually causes 16 times as much damage. Wheels cause the road to flex slightly, resulting in fatigue cracking, which often leads to crocodile cracking. Vehicle speed also plays a role. Slowly moving vehicles stress the road over a longer period of time, increasing ruts, cracking, and corrugations in the asphalt pavement.

Other causes of damage include heat damage from vehicle fires, or solvent action from chemical spills.

The life of a road can be prolonged through good design, construction and maintenance practices. During design, engineers measure the traffic on a road, paying special attention to the number and types of trucks. They also evaluate the subsoil to see how much load it can withstand. The pavement and subbase thicknesses are designed to withstand the wheel loads. Sometimes, geogrids are used to reinforce the subbase and further strengthen the roads. Drainage, including ditches, storm drains and underdrains are used to remove water from the roadbed, preventing it from weakening the subbase and subsoil.

Good maintenance practices center on keeping water out of the pavement, subbase and subsoil. Maintaining and cleaning ditches and storm drains will extend the life of the road at low cost. Sealing small cracks with bituminous crack sealer prevents water from enlarging cracks through frost weathering, or percolating down to the subbase and softening it.

For somewhat more distressed roads, a chip seal or similar surface treatment may be applied. As the number, width and length of cracks increases, more intensive repairs are needed. In order of generally increasing expense, these include thin asphalt overlays, multicourse overlays, grinding off the top course and overlaying, in-place recycling, or full-depth reconstruction of the roadway.

It is far less expensive to keep a road in good condition than it is to repair it once it has deteriorated. This is why some agencies place the priority on preventive maintenance of roads in good condition, rather than reconstructing roads in poor condition. Poor roads are upgraded as resources and budget allow. In terms of lifetime cost and long term pavement conditions, this will result in better system performance. Agencies that concentrate on restoring their bad roads often find that by the time they've repaired them all, the roads that were in good condition have deteriorated.[17]

Some agencies use a pavement management system to help prioritize maintenance and repairs.

A small-scale asphalt recycler

Asphalt concrete is 100% recyclable and is the most widely reused construction material in the world. Very little asphalt concrete — less than 1 percent, according to a 2011 survey by the Federal Highway Administration and the National Asphalt Pavement Association — is actually disposed of in landfills.[18]

There is asphalt recycling on a large scale (known as in-place asphalt recycling or asphalt recycling performed at a hot mix plant) and asphalt recycling on a smaller scale. For small scale asphalt recycling, the user separates asphalt material into three different categories:

Blacktop cookies Chunks of virgin uncompacted hot mix asphalt which can be used for pothole repair. The use of blacktop cookies has been investigated as a less expensive, less labor-intensive, more durable alternative to repairing potholes with cold patch. In a program in Pittsfield, Massachusetts, workers purchased new hot mix asphalt and spread it liberally on the ground to produce approximately 25 lb. wafers. Once cooled, the wafers could be stored until reheated in a hotbox to make minor road repairs. Blacktop cookies may also be produced from leftover material from paving jobs.[19] Reclaimed asphalt pavement (RAP) Chunks of asphalt that have been removed from a road, parking lot or driveway are considered RAP. These chunks of asphalt typically are ripped up when making a routine asphalt repair, man hole repair, catch basin repair or sewer main repair. Because the asphalt has been compacted, RAP is a denser asphalt material and typically takes longer to recycle than blacktop cookies. Asphalt millings Small pieces of asphalt produced by mechanically grinding asphalt surfaces are referred to as asphalt millings. Large millings that have a rich, black tint indicating a high asphalt cement content are best for asphalt recycling purposes. Surface millings are recommended over full depth millings when choosing asphalt millings to recycle. Full depth millings usually contain sub-base contaminants such as gravel, mud and sand. These sub base contaminants will leach oil away from original asphalt and dry out the material in the recycling process. Asphalt milled from asphalt is better than asphalt milled from concrete. When milling asphalt from concrete the dust that is created is not compatible with asphalt products because it is not asphalt.[20]

Small scale asphalt recycling will usually involve high speed on-site asphalt recycling equipment or overnight soft heat asphalt recycling.

Small scale asphalt recycling is used when wanting to make smaller road repairs vs. large scale asphalt recycling which is done for making new asphalt or for tearing up old asphalt and simultaneously recycling / replacing existing asphalt. Recycled asphalt is very effective for pothole and utility cut repairs. The recycled asphalt will generally last as long or longer than the road around it as new asphalt cement has been added back to the material.[21]

For larger scale asphalt recycling, several in-place recycling techniques have been developed to rejuvenate oxidized binders and remove cracking, although the recycled material is generally not very water-tight or smooth and should be overlaid with a new layer of asphalt concrete. Cold in-place recycling mills off the top layers of asphalt concrete and mixes the resulting loose millings with asphalt emulsion. The mixture is then placed back down on the roadway and compacted. The water in the emulsion is allowed to evaporate for a week or so, and new hot-mix asphalt is laid on top.

Asphalt concrete that is removed from a pavement is usually stockpiled for later use as aggregate for new hot mix asphalt at an asphalt plant. This reclaimed material, or RAP, is crushed to a consistent gradation and added to the HMA mixing process. Sometimes waste materials, such as asphalt roofing shingles, crushed glass, or rubber from old tires, are added to asphalt concrete as is the case with rubberized asphalt, but there is a concern that the hybrid material may not be recyclable.

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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Parking Lot Contractors in JHB except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Asphalt Companies In My Area is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Parking Lot Contractors Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Asphalt Driveway Sealing Services the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Crocodile cracking

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Paver Repair Quotes Raised sidewalks beside a 2000-year-old paved road, Pompeii, Italy

A sidewalk (American English) or pavement (British English), also known as a footpath or footway, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade (height) and is normally separated from the vehicular section by a curb. There may also be a median strip or road verge (a strip of vegetation, grass or bushes or trees or a combination of these) either between the sidewalk and the roadway or between the sidewalk and the boundary.

In some places, the same term may also be used for a paved path, trail or footpath that is not next to a road, for example, a path through a park.

The term "sidewalk" is usually preferred in most of North America, along with many other countries worldwide that are not members of the Commonwealth of Nations. The term "pavement" is more common in the United Kingdom,[1] as well as parts of the Mid-Atlantic United States such as Philadelphia and New Jersey.[2][3] Many Commonwealth countries use the term "footpath". The professional, civil engineering and legal term for this in North America is "sidewalk" while in the United Kingdom it is "footway".[4]

In the United States, the term sidewalk is used for the pedestrian path beside a road. "Shared use paths" or "multi-use paths" are available for use by both pedestrians and bicyclists.[5] "Walkway" is a more comprehensive term that includes stairs, ramps, passageways, and related structures that facilitate the use of a path as well as the sidewalk.[6]

In the UK, the term "footpath" is mostly used for paths that do not abut a roadway.[7] The term "shared-use path" is used where cyclists are also able to use the same section of path as pedestrians.[8]

East India House, Leadenhall Street, London, 1766. The sidewalk is separated from the main street by six bollards in front of the building.

There is evidence that sidewalks were built in ancient times. It was claimed that the Greek city of Corinth was paved by the 4th-century, and the Romans were particularly prolific sidewalk builders – they called them semitas.[9]

However, by the Middle Ages, narrow roads had reverted to being simultaneously used by pedestrians and wagons without any formal separation between the two categories. Early attempts at ensuring the adequate maintenance of foot-ways or sidewalks were often made, such as the 1623 Act for Colchester, although they were generally not very effective.[10]

Following the Great Fire of London in 1666, attempts were slowly made to bring some order to the sprawling city. In 1671, 'Certain Orders, Rules and Directions Touching the Paving and Cleansing The Streets, Lanes and Common Passages within the City of London' were formulated, calling for all streets to be adequately paved for pedestrians with cobblestones. Purbeck stone was widely used as a durable paving material. Bollards were also installed to protect pedestrians from the traffic in the middle of the road.

A series of Paving Acts from the House of Commons during the 18th century, especially the 1766 Paving & Lighting Act, authorized the City of London Corporation to create foot-ways throughout all the streets of London, to pave them with Purbeck stone (the thoroughfare in the middle was generally cobblestone) and to raise them above the street level with curbs forming the separation.[11] The Corporation was also made responsible for the regular upkeep of the roads, including their cleaning and repair, for which they charged a tax from 1766.[12] By the late 19th-century large and spacious sidewalks were routinely constructed in European capitals, and were associated with urban sophistication.

In the United States, adjoining property owners must in most situations finance all or part of the cost of sidewalk construction. In a legal case in 1917 involving E. L. Stewart, a former member of the Louisiana House of Representatives and a lawyer in Minden in Webster Parish, the Louisiana Supreme Court ruled that owners must pay whether they wish for the sidewalk to be constructed or not.[13]

Pedestrians walking on the pavement (sidewalk) in London.

Sidewalks play an important role in transportation, as they provide a safe path for people to walk along that is separated from the motorized traffic. They aid road safety by minimizing interaction between pedestrians and motorized traffic. Sidewalks are normally in pairs, one on each side of the road, with the center section of the road for motorized vehicles.

In rural roads, sidewalks may not be present as the amount of traffic (pedestrian or motorized) may not be enough to justify separating the two. In suburban and urban areas, sidewalks are more common. In town and city centers (known as downtown in North America) the amount of pedestrian traffic can exceed motorized traffic, and in this case the sidewalks can occupy more than half of the width of the road, or the whole road can be reserved for pedestrians, see Pedestrian zone.

Sidewalks may have a small effect on reducing vehicle miles traveled and carbon dioxide emissions. A study of sidewalk and transit investments in Seattle neighborhoods found vehicle travel reductions of 6 to 8% and CO2 emission reductions of 1.3 to 2.2% [14]

Sidewalk with bike path See also: Road traffic safety

Research commissioned for the Florida Department of Transportation, published in 2005, found that, in Florida, the Crash Reduction Factor (used to estimate the expected reduction of crashes during a given period) resulting from the installation of sidewalks averaged 74%.[15] Research at the University of North Carolina for the U.S. Department of Transportation found that the presence or absence of a sidewalk and the speed limit are significant factors in the likelihood of a vehicle/pedestrian crash. Sidewalk presence had a risk ratio of 0.118, which means that the likelihood of a crash on a road with a paved sidewalk was 88.2 percent lower than one without a sidewalk. “This should not be interpreted to mean that installing sidewalks would necessarily reduce the likelihood of pedestrian/motor vehicle crashes by 88.2 percent in all situations. However, the presence of a sidewalk clearly has a strong beneficial effect of reducing the risk of a ‘walking along roadway’ pedestrian/motor vehicle crash.” The study does not count crashes that happen when walking across a roadway. The speed limit risk ratio was 1.116, which means that a 16.1-km/h (10-mi/h) increase in the limit yields a factor of (1.116)10 or 3.[16]

The presence or absence of sidewalks was one of three factors that were found to encourage drivers to choose lower, safer speeds.[17]

On the other hand, the implementation of schemes which involve the removal of sidewalks, such as shared space schemes, are reported to deliver a dramatic drop in crashes and congestion too, which indicates that a number of other factors, such as the local speed environment, also play an important role in whether sidewalks are necessarily the best local solution for pedestrian safety.[18]

In cold weather, black ice is a common problem with unsalted sidewalks. The ice forms a thin transparent surface film which is almost impossible to see, and so results in many slips by pedestrians.

Riding bicycles on sidewalks is discouraged since some research shows it to be more dangerous than riding in the street.[19] Some jurisdictions prohibit sidewalk riding except for children. In addition to the risk of cyclist/pedestrian collisions, cyclists face increase risks from collisions with motor vehicles at street crossings and driveways. Riding in the direction opposite to traffic in the adjacent lane is especially risky.[20]

Since residents of neighborhoods with sidewalks are more likely to walk, they tend to have lower rates of cardiovascular disease, obesity, and other health issues related to sedentary lifestyles.[21] Also, children who walk to school have been shown to have better concentration.[22]

Native Americans busking at Orchard Road, Singapore

Some sidewalks may be used as social spaces with sidewalk cafes, markets, or busking musicians, as well as for parking for a variety of vehicles including cars, motorbikes and bicycles.

Contemporary sidewalks are most often made of concrete in the United States and Canada, while tarmac, asphalt, brick, stone, slab and (increasingly) rubber are more common in Europe.[23] Different materials are more or less friendly environmentally: pumice-based trass, for example, when used as an extender is less energy-intensive than Portland cement concrete or petroleum-based materials such as asphalt or tar-penetration macadam). Multi-use paths alongside roads are sometimes made of materials that are softer than concrete, such as asphalt.

In the 19th century and early 20th century, sidewalks of wood were common in some North American locations. They may still be found at historic beach locations and in conservation areas to protect the land beneath and around, called boardwalks.

Brick sidewalks are found in some urban areas, usually for aesthetic purposes. Brick sidewalk construction usually involves the usage of a mechanical vibrator to lock the bricks in place after they have been laid (and/or to prepare the soil before laying). Although this might also be done by other tools (as regular hammers and heavy rolls), a vibrator is often used to speed up the process.

Stone slabs called flagstones or flags are sometimes used where an attractive appearance is required, as in historic town centers. In other places, pre-cast concrete slabs (called paving slabs or, less correctly, paving stones) are used. These may be colored or textured to resemble stone.

Freshly laid concrete sidewalk, with horizontal strain-relief grooves faintly visible

In the United States and Canada, the most common type of sidewalk consists of a poured concrete ribbon, examples of which from as early as the 1860s can be found in good repair in San Francisco, and stamped with the name of the contractor and date of installation.[citation needed] When quantities of Portland cement were first imported to the United States in the 1880s, its principal use was in the construction of sidewalks.[24]

Today, most sidewalk ribbons are constructed with cross-lying strain-relief grooves placed or sawn at regular intervals typically 5 feet (1.5 m) apart. This partitioning, an improvement over the continuous slab, was patented in 1924 by Arthur Wesley Hall and William Alexander McVay, who wished to minimize damage to the concrete from the effects of tectonic and temperature fluctuations, both of which can crack longer segments.[25] The technique is not perfect, as freeze-thaw cycles (in cold-weather regions) and tree root growth can eventually result in damage which requires repair.

In highly variable climates which undergo multiple freeze-thaw cycles, the concrete blocks will be separated by expansion joints to allow for thermal expansion without breakage. The use of expansion joints in sidewalks may not be necessary, as the concrete will shrink while setting.[26]

In the United Kingdom, Australia and France suburban sidewalks are most commonly constructed of tarmac. In urban or inner-city areas sidewalks are most commonly constructed of slabs, stone, or brick depending upon the surrounding street architecture and furniture.

Brick

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Bleeding or flushing is shiny, black surface film of asphalt on the road surface caused by upward movement of asphalt in the pavement surface.[1][2] Common causes of bleeding are too much asphalt in asphalt concrete, hot weather, low space air void content and quality of asphalt.[3]

Bleeding is a safety concern since it results in a very smooth surface, without the texture required to prevent hydroplaning.

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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Parking Lot Maintenance in Westcliff except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Asphalt Driveway Sealing Contractors is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Parking Lot Maintenance Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Best Way To Clean Driveway Pavers the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Diverging diamond interchange

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Asphalt Contractors Near Me For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)mən, bˈt(j)mən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.[3] The word is derived from the Ancient Greek ἄσφαλτος ásphaltos.[4]

The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.[5]

The terms "asphalt" and "bitumen" are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" (or "asphalt cement") is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called "bitumen", and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.

Naturally occurring asphalt is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.[8]

The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch",[9] which perhaps derives from ἀ-, "without" and σφάλλω (sfallō), "make fall".[10] The first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads.

The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", and jatu-krit, meaning "pitch creating" or "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.[12]

In British English, "bitumen" is used instead of "asphalt". The word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called "tarmac" in common parlance). Bitumen mixed with clay was usually called "asphaltum",[13] but the term is less commonly used today.[citation needed]

In Australian English, "bitumen" is often used as the generic term for road surfaces.

In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is also commonly used as a shortened form of "asphalt concrete" (therefore equivalent to the British "asphalt" or "tarmac").

In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while "asphalt" is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", and syncrude blended with bitumen is called "synbit".[15]

"Bitumen" is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

Neither of the terms "asphalt" or "bitumen" should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.[5]

The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] "It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".[17]

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word "tarmac", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US. The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.[8]

The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.[21]

Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.[19]

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.[22]

Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.[21]

The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.[26]

The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.[27]

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians' primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.[31]

In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.[21]

In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.[33]

An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".[34]

But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.[36]

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon's Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.[38]

The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.[36]

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge.[35][44][45][46] Claridge's Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France",[47]—"laid one of the first asphalt pavements in Whitehall".[48] Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,[47][49] "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park".[49] "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry".[45] "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production",[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".[51]

In 1838, there was a flurry of entrepreneurial activity involving asphalt, which had uses beyond paving. For example, asphalt could also be used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, both of which were also proliferating in the 19th century.[3][35][52] On the London stockmarket, there were various claims as to the exclusivity of asphalt quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s".[50]

In 1914, Claridge's Company entered into a joint venture to produce tar-bound macadam,[53] with materials manufactured through a subsidiary company called Clarmac Roads Ltd.[54] Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridge's Patent Asphalte Co., although Clarmac was more widely used.[55][note 1] However, the First World War ruined the Clarmac Company, which entered into liquidation in 1915.[57][58] The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up,[59] ceasing operations in 1917,[60][61] having invested a substantial amount of funds into the new venture, both at the outset[59] and in a subsequent attempt to save the Clarmac Company.[57]

The first use of bitumen in the New World was by indigenous peoples. On the west coast, as early as the 13th century, the Tongva, Luiseño and Chumash peoples collected the naturally occurring bitumen that seeped to the surface above underlying petroleum deposits. All three groups used the substance as an adhesive. It is found on many different artifacts of tools and ceremonial items. For example, it was used on rattles to adhere gourds or turtle shells to rattle handles. It was also used in decorations. Small round shell beads were often set in asphaltum to provide decorations. It was used as a sealant on baskets to make them watertight for carrying water, possibly poisoning those who drank the water.[62] Asphalt was used also to seal the planks on ocean-going canoes.

Asphalt was first used to pave streets in the 1870s. At first naturally occurring "bituminous rock" was used, such as at Ritchie Mines in Macfarlan in Ritchie County, West Virginia from 1852 to 1873. In 1876, asphalt-based paving was used to pave Pennsylvania Avenue in Washington DC, in time for the celebration of the national centennial.[63] In the horse-drawn era, streets were unpaved and covered with dirt or gravel. However, that produced uneven wear, opened new hazards for pedestrians and made for dangerous potholes for bicycles and for motor vehicles. Manhattan alone had 130,000 horses in 1900, pulling streetcars, wagons, and carriages, and leaving their waste behind. They were not fast, and pedestrians could dodge and scramble their way across the crowded streets. Small towns continued to rely on dirt and gravel, but larger cities wanted much better streets. They looked to wood or granite blocks by the 1850s.[64] In 1890, a third of Chicago's 2000 miles of streets were paved, chiefly with wooden blocks, which gave better traction than mud. Brick surfacing was a good compromise, but even better was asphalt paving, which was easy to install and to cut through to get at sewers. With London and Paris serving as models, Washington laid 400,000 square yards of asphalt paving by 1882; it became the model for Buffalo, Philadelphia and elsewhere. By the end of the century, American cities boasted 30 million square yards of asphalt paving, well ahead of brick.[65] The streets became faster and more dangerous so electric traffic lights were installed. Electric trolleys (at 12 miles per hour) became the main transportation service for middle class shoppers and office workers until they bought automobiles after 1945 and commuted from more distant suburbs in privacy and comfort on asphalt highways.[66]

See also: Bitumount and History of the petroleum industry in Canada (oil sands and heavy oil)

Canada has the world's largest deposit of natural bitumen in the Athabasca oil sands, and Canadian First Nations along the Athabasca River had long used it to waterproof their canoes. In 1719, a Cree named Wa-Pa-Su brought a sample for trade to Henry Kelsey of the Hudson’s Bay Company, who was the first recorded European to see it. However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."[21]

The value of the deposit was obvious from the start, but the means of extracting the bitumen was not. The nearest town, Fort McMurray, Alberta, was a small fur trading post, other markets were far away, and transportation costs were too high to ship the raw bituminous sand for paving. In 1915, Sidney Ells of the Federal Mines Branch experimented with separation techniques and used the product to pave 600 feet of road in Edmonton, Alberta. Other roads in Alberta were paved with material extracted from oil sands, but it was generally not economic. During the 1920s Dr. Karl A. Clark of the Alberta Research Council patented a hot water oil separation process and entrepreneur Robert C. Fitzsimmons[67] built the Bitumount oil separation plant, which between 1925 and 1958 produced up to 300 barrels (50 m3) per day of bitumen using Dr. Clark's method. Most of the bitumen was used for waterproofing roofs, but other uses included fuels, lubrication oils, printers ink, medicines, rust- and acid-proof paints, fireproof roofing, street paving, patent leather, and fence post preservatives.[21] Eventually Fitzsimmons ran out of money and the plant was taken over by the Alberta government. Today the Bitumount plant is a Provincial Historic Site.[68]

Bitumen was used in early photographic technology. In 1826 or 1827, it was used by French scientist Joseph Nicéphore Niépce to make the oldest surviving photograph from nature. The bitumen was thinly coated onto a pewter plate which was then exposed in a camera. Exposure to light hardened the bitumen and made it insoluble, so that when it was subsequently rinsed with a solvent only the sufficiently light-struck areas remained. Many hours of exposure in the camera were required, making bitumen impractical for ordinary photography, but from the 1850s to the 1920s it was in common use as a photoresist in the production of printing plates for various photomechanical printing processes.[69][70]

Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle.[71]

The vast majority of refined asphalt is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use, asphalt is produced to specification. This is achieved either by refining or blending. It is estimated that the current world use of asphalt is approximately 102 million tonnes per year. Approximately 85% of all the asphalt produced is used as the binder in asphalt concrete for roads. It is also used in other paved areas such as airport runways, car parks and footways. Typically, the production of asphalt concrete involves mixing fine and coarse aggregates such as sand, gravel and crushed rock with asphalt, which acts as the binding agent. Other materials, such as recycled polymers (e.g., rubber tyres), may be added to the asphalt to modify its properties according to the application for which the asphalt is ultimately intended.

A further 10% of global asphalt production is used in roofing applications, where its waterproofing qualities are invaluable. The remaining 5% of asphalt is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet tile backing and paint. Asphalt is applied in the construction and maintenance of many structures, systems, and components, such as the following:

Main article: Asphalt concrete

The largest use of asphalt is for making asphalt concrete for road surfaces; this accounts for approximately 85% of the asphalt consumed in the United States. Asphalt concrete pavement mixes are typically composed of 5% asphalt cement and 95% aggregates (stone, sand, and gravel). Due to its highly viscous nature, asphalt cement must be heated so it can be mixed with the aggregates at the asphalt mixing facility. The temperature required varies depending upon characteristics of the asphalt and the aggregates, but warm-mix asphalt technologies allow producers to reduce the temperature required. There are about 4,000 asphalt concrete mixing plants in the US, and a similar number in Europe.[72]

When maintenance is performed on asphalt pavements, such as milling to remove a worn or damaged surface, the removed material can be returned to a facility for processing into new pavement mixtures. The asphalt in the removed material can be reactivated and put back to use in new pavement mixes.[73] With some 95% of paved roads being constructed of or surfaced with asphalt,[74] a substantial amount of asphalt pavement material is reclaimed each year. According to industry surveys conducted annually by the Federal Highway Administration and the National Asphalt Pavement Association, more than 99% of the asphalt removed each year from road surfaces during widening and resurfacing projects is reused as part of new pavements, roadbeds, shoulders and embankments.[75]

Asphalt concrete paving is widely used in airports around the world. Due to the sturdiness and ability to be repaired quickly, it is widely used for runways.

Further information: Fibre mastic asphalt

Mastic asphalt is a type of asphalt that differs from dense graded asphalt (asphalt concrete) in that it has a higher asphalt (binder) content, usually around 7–10% of the whole aggregate mix, as opposed to rolled asphalt concrete, which has only around 5% asphalt. This thermoplastic substance is widely used in the building industry for waterproofing flat roofs and tanking underground. Mastic asphalt is heated to a temperature of 210 °C (410 °F) and is spread in layers to form an impervious barrier about 20 millimeters (0.8 inches) thick.

A number of technologies allow asphalt to be mixed at much lower temperatures. These involve mixing with petroleum solvents to form "cutbacks" with reduced melting point or mixing with water to turn the asphalt into an emulsion. Asphalt emulsions contain up to 70% asphalt and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock, gravel or crushed slag. Slurry seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on the surface of a road. Cold-mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth, and asphalt emulsions are also blended into recycled hot-mix asphalt to create low-cost pavements.

Main article: Synthetic crude oil See also: Petroleum production in Canada

Synthetic crude oil, also known as syncrude, is the output from a bitumen upgrader facility used in connection with oil sand production in Canada. Bituminous sands are mined using enormous (100 ton capacity) power shovels and loaded into even larger (400 ton capacity) dump trucks for movement to an upgrading facility. The process used to extract the bitumen from the sand is a hot water process originally developed by Dr. Karl Clark of the University of Alberta during the 1920s. After extraction from the sand, the bitumen is fed into a bitumen upgrader which converts it into a light crude oil equivalent. This synthetic substance is fluid enough to be transferred through conventional oil pipelines and can be fed into conventional oil refineries without any further treatment. By 2015 Canadian bitumen upgraders were producing over 1 million barrels (160×10^3 m3) per day of synthetic crude oil, of which 75% was exported to oil refineries in the United States.[76]

In Alberta, five bitumen upgraders produce synthetic crude oil and a variety of other products: The Suncor Energy upgrader near Fort McMurray, Alberta produces synthetic crude oil plus diesel fuel; the Syncrude Canada, Canadian Natural Resources, and Nexen upgraders near Fort McMurray produce synthetic crude oil; and the Shell Scotford Upgrader near Edmonton produces synthetic crude oil plus an intermediate feedstock for the nearby Shell Oil Refinery.[77] A sixth upgrader, under construction in 2015 near Redwater, Alberta, will upgrade half of its crude bitumen directly to diesel fuel, with the remainder of the output being sold as feedstock to nearby oil refineries and petrochemical plants.[78]

See also: Western Canadian Select

Canadian bitumen does not differ substantially from oils such as Venezuelan extra-heavy and Mexican heavy oil in chemical composition, and the real difficulty is moving the extremely viscous bitumen through oil pipelines to the refinery. Many modern oil refineries are extremely sophisticated and can process non-upgraded bitumen directly into products such as gasoline, diesel fuel, and refined asphalt without any preprocessing. This is particularly common in areas such as the US Gulf coast, where refineries were designed to process Venezuelan and Mexican oil, and in areas such as the US Midwest where refineries were rebuilt to process heavy oil as domestic light oil production declined. Given the choice, such heavy oil refineries usually prefer to buy bitumen rather than synthetic oil because the cost is lower, and in some cases because they prefer to produce more diesel fuel and less gasoline.[77] By 2015 Canadian production and exports of non-upgraded bitumen exceeded that of synthetic crude oil at over 1.3 million barrels (210×10^3 m3) per day, of which about 65% was exported to the United States.[76]

Because of the difficulty of moving crude bitumen through pipelines, non-upgraded bitumen is usually diluted with natural-gas condensate in a form called dilbit or with synthetic crude oil, called synbit. However, to meet international competition, much non-upgraded bitumen is now sold as a blend of multiple grades of bitumen, conventional crude oil, synthetic crude oil, and condensate in a standardized benchmark product such as Western Canadian Select. This sour, heavy crude oil blend is designed to have uniform refining characteristics to compete with internationally marketed heavy oils such as Mexican Mayan or Arabian Dubai Crude.[77]

Asphalt was used starting in the 1960s as an hydrophobic matrix aiming to encapsulate radioactive waste such as medium-activity salts (mainly soluble sodium nitrate and sodium sulfate) produced by the reprocessing of spent nuclear fuels or radioactive sludges from sedimentation ponds.[79][80] Bituminised radioactive waste containing highly radiotoxic alpha-emitting transuranic elements from nuclear reprocessing plants have been produced at industrial scale in France, Belgium and Japan, but this type of waste conditioning has been abandoned because operational safety issues (risks of fire, as occurred in a bituminisation plant at Tokai Works in Japan)[81][82] and long-term stability problems related to their geological disposal in deep rock formations. One of the main problem is the swelling of asphalt exposed to radiation and to water. Asphalt swelling is first induced by radiation because of the presence of hydrogen gas bubbles generated by alpha and gamma radiolysis.[83][84] A second mechanism is the matrix swelling when the encapsulated hygroscopic salts exposed to water or moisture start to rehydrate and to dissolve. The high concentration of salt in the pore solution inside the bituminised matrix is then responsible for osmotic effects inside the bituminised matrix. The water moves in the direction of the concentrated salts, the asphalt acting as a semi-permeable membrane. This also causes the matrix to swell. The swelling pressure due to osmotic effect under constant volume can be as high as 200 bar. If not properly managed, this high pressure can cause fractures in the near field of a disposal gallery of bituminised medium-level waste. When the bituminised matrix has been altered by swelling, encapsulated radionuclides are easily leached by the contact of ground water and released in the geosphere. The high ionic strength of the concentrated saline solution also favours the migration of radionuclides in clay host rocks. The presence of chemically reactive nitrate can also affect the redox conditions prevailing in the host rock by establishing oxidizing conditions, preventing the reduction of redox-sensitive radionuclides. Under their higher valences, radionuclides of elements such as selenium, technetium, uranium, neptunium and plutonium have a higher solubility and are also often present in water as non-retarded anions. This makes the disposal of medium-level bituminised waste very challenging.

Different type of asphalt have been used: blown bitumen (partly oxidized with air oxygen at high temperature after distillation, and harder) and direct distillation bitumen (softer). Blown bitumens like Mexphalte, with a high content of saturated hydrocarbons, are more easily biodegraded by microorganisms than direct distillation bitumen, with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons.[85]

Concrete encapsulation of radwaste is presently considered a safer alternative by the nuclear industry and the waste management organisations.

Roofing shingles account for most of the remaining asphalt consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Asphalt is used to make Japan black, a lacquer known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker.[86] Asphalt is also used to seal some alkaline batteries during the manufacturing process.

Typical asphalt plant for making asphalt

About 40,000,000 tons were produced in 1984.[needs update] It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as naphtha, gasoline and diesel). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude asphalt is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This step makes the product harder and more viscous.[5]

Asphalt is typically stored and transported at temperatures around 150 °C (302 °F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.

Main article: Oil sands

Naturally occurring crude bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from "oil sands", currently under development in Alberta, Canada. Canada has most of the world's supply of natural bitumen, covering 140,000 square kilometres[14] (an area larger than England), giving it the second-largest proven oil reserves in the world. The Athabasca oil sands are the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods. Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020.[15] The total amount of crude bitumen in Alberta that could be extracted is estimated to be about 310 billion barrels (50×10^9 m3),[8] which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.

Main articles: Peak oil, Global warming, and Bioasphalt

Although uncompetitive economically, asphalt can be made from nonpetroleum-based renewable resources such as sugar, molasses and rice, corn and potato starches. Asphalt can also be made from waste material by fractional distillation of used motor oil, which is sometimes otherwise disposed of by burning or dumping into landfills. Use of motor oil may cause premature cracking in colder climates, resulting in roads that need to be repaved more frequently.[87]

Nonpetroleum-based asphalt binders can be made light-colored. Lighter-colored roads absorb less heat from solar radiation, reducing their contribution to the urban heat island effect.[88] Parking lots that use asphalt alternatives are called green parking lots.

Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania, the only European asphalt mine still in use. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring and ball) around 120 °C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.

Albanian bitumen extraction has a long history and was practiced in an organized way by the Romans. After centuries of silence, the first mentions of Albanian bitumen appeared only in 1868, when the Frenchman Coquand published the first geological description of the deposits of Albanian bitumen. In 1875, the exploitation rights were granted to the Ottoman government and in 1912, they were transferred to the Italian company Simsa. Since 1945, the mine was exploited by the Albanian government and from 2001 to date, the management passed to a French company, which organized the mining process for the manufacture of the natural bitumen on an industrial scale.[89]

Today the mine is predominantly exploited in an open pit quarry but several of the many underground mines (deep and extending over several km) still remain viable. Selenizza is produced primarily in granular form, after melting the bitumen pieces selected in the mine.

Selenizza[90] is mainly used as an additive in the road construction sector. It is mixed with traditional asphalt to improve both the viscoelastic properties and the resistance to ageing. It may be blended with the hot asphalt in tanks, but its granular form allows it to be fed in the mixer or in the recycling ring of normal asphalt plants. Other typical applications include the production of mastic asphalts for sidewalks, bridges, car-parks and urban roads as well as drilling fluid additives for the oil and gas industry. Selenizza is available in powder or in granular material of various particle sizes and is packaged in sacks or in thermal fusible polyethylene bags.

A life-cycle assessment study of the natural selenizza compared with petroleum asphalt has shown that the environmental impact of the selenizza is about half the impact of the road asphalt produced in oil refineries in terms of carbon dioxide emission.[91]

People can be exposed to asphalt in the workplace by breathing in fumes or skin absorption. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit of 5 mg/m3 over a 15-minute period.[92]

Asphalt is basically an inert material that must be heated or diluted to a point where it becomes workable for the production of materials for paving, roofing, and other applications. In examining the potential health hazards associated with asphalt, the International Agency for Research on Cancer (IARC) determined that it is the application parameters, predominantly temperature, that affect occupational exposure and the potential bioavailable carcinogenic hazard/risk of the asphalt emissions.[93] In particular, temperatures greater than 199 °C (390 °F), were shown to produce a greater exposure risk than when asphalt was heated to lower temperatures, such as those typically used in asphalt pavement mix production and placement.[94] IARC has classified asphalt as a Class 2B possible carcinogen.

An asphalt mixing plant for hot aggregate
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  56. ^ Roads laid with Clarmac The Building News and Engineering Journal, 1915 109 (3157), p.3 (n14 in electronic field).
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Road surface

Asphalt Road Price Not to be confused with cement or mortar (masonry). Exterior of the Roman Pantheon, finished 128 AD, the largest unreinforced concrete dome in the world.[1] Interior of the Pantheon dome, seen from beneath. The concrete for the coffered dome was laid on moulds, probably mounted on temporary scaffolding. Opus caementicium exposed in a characteristic Roman arch. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone.

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time. Most concretes used are lime-based concretes such as Portland cement concrete or concretes made with other hydraulic cements, such as calcium aluminate cements. However, asphalt concrete, which is frequently used for road surfaces, is also a type of concrete, where the cement material is bitumen, and polymer concretes are sometimes used where the cementing material is a polymer.

When aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses.[2] Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.

Famous concrete structures include the Hoover Dam, the Panama Canal, and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, and concrete was widely used in the Roman Empire. The Colosseum in Rome was built largely of concrete, and the concrete dome of the Pantheon is the world's largest unreinforced concrete dome.[3] Today, large concrete structures (for example, dams and multi-storey car parks) are usually made with reinforced concrete.

After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Today, concrete is the most widely used human-made material (measured by tonnage).[citation needed]

The word concrete comes from the Latin word "concretus" (meaning compact or condensed),[4] the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Small-scale usage of concrete has been documented to be thousands of years old. Concrete-like materials were used since 6500 BC by the Nabataea traders or Bedouins, who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan. They discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. They kept the cisterns secret as these enabled the Nabataea to thrive in the desert.[5] Some of these structures survive to this day.[5]

In the Ancient Egyptian and later Roman eras, builders re-discovered that adding volcanic ash to the mix allowed it to set underwater.

German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400–1200 BC.[6][7] Lime mortars were used in Greece, Crete, and Cyprus in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete.[8] Concrete was used for construction in many ancient structures.[9]

The Romans used concrete extensively from 300 BC to 476 AD, a span of more than seven hundred years.[10] During the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension.[11]

Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.[12]

Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2 [20 MPa; 2,800 psi]).[13] However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, and its mode of application was also different:[14]

Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.[15]

The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby crystallization of strätlingite and the coalescence of calcium–aluminum-silicate–hydrate cementing binder helped give the concrete a greater degree of fracture resistance even in seismically active environments.[16] Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al-tobermorite crystals over time.[17][18]

Smeaton's Tower

The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon.

After the Roman Empire, the use of burned lime and pozzolana was greatly reduced until the technique was all but forgotten between 500 and the 14th century. From the 14th century to the mid-18th century, the use of cement gradually returned. The Canal du Midi was built using concrete in 1670.[19]

Perhaps the greatest driver behind the modern use of concrete was Smeaton's Tower, the third Eddystone Lighthouse in Devon, England. To create this structure, between 1756 and 1759, British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.[20]

Developed in England in the 19th century, a method for producing Portland cement was patented by Joseph Aspdin in 1824.[21] Aspdin named it due to its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England. His son William Aspdin is regarded as the inventor of "modern" Portland cement due to his developments in the 1840s.[22]

Reinforced concrete was invented in 1849 by Joseph Monier.[23] In 1889 the first concrete reinforced bridge was built, and the first large concrete dams were built in 1936, Hoover Dam and Grand Coulee Dam.[24]

Many types of concrete are available, distinguished by the proportions of the main ingredients below. In this way or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application. Strength, density, as well chemical and thermal resistance are variables.

Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand.

Cement, most commonly Portland cement, is associated with the general term "concrete." A range of other materials can be used as the cement in concrete too. One of the most familiar of these alternative cements is asphalt concrete. Other cementitious materials such as fly ash and slag cement, are sometimes added as mineral admixtures (see below) - either pre-blended with the cement or directly as a concrete component - and become a part of the binder for the aggregate.

To produce concrete from most cements (excluding asphalt), water is mixed with the dry powder and aggregate, which produces a semi-liquid slurry that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, creating a robust stone-like material.

Chemical admixtures are added to achieve varied properties. These ingredients may accelerate or slow down the rate at which the concrete hardens, and impart many other useful properties including increased tensile strength, entrainment of air and water resistance.

Reinforcement is often included in concrete. Concrete can be formulated with high compressive strength, but always has lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension, typically steel rebar.

Mineral admixtures have become more popular over recent decades. The use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation, and the discovery that such materials often have complementary and valuable properties. The most conspicuous of these are fly ash, a by-product of coal-fired power plants, ground granulated blast furnace slag, a byproduct of steelmaking, and silica fume, a byproduct of industrial electric arc furnaces. The use of these materials in concrete reduces the amount of resources required, as the mineral admixtures act as a partial cement replacement. This displaces some cement production, an energetically expensive and environmentally problematic process, while reducing the amount of industrial waste that must be disposed of. Mineral admixtures can be pre-blended with the cement during its production for sale and use as a blended cement, or mixed directly with other components when the concrete is produced.

The mix design depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure.

Main article: Cement A few tons of bagged cement. This amount represents about two minutes of output from a 10,000 ton per day cement kiln.

Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar and many plasters. British masonry worker Joseph Aspdin patented Portland cement in 1824. It was named because of the similarity of its colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of calcium silicates (alite, belite), aluminates and ferrites - compounds which combine calcium, silicon, aluminium and iron in forms which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminium and iron) and grinding this product (called clinker) with a source of sulfate (most commonly gypsum).

In modern cement kilns many advanced features are used to lower the fuel consumption per ton of clinker produced. Cement kilns are extremely large, complex, and inherently dusty industrial installations, and have emissions which must be controlled. Of the various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement. Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels.[25]

Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely.[26]

As stated by Abrams' law, a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump.[27] Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.[28]

Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles and other components of the concrete to form a solid mass.[29]

Reaction:[29]

Cement chemist notation: C3S + H → C-S-H + CH Standard notation: Ca3SiO5 + H2O → (CaO)·(SiO2)·(H2O)(gel) + Ca(OH)2 Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2 (approximately; the exact ratios of the CaO, SiO2 and H2O in C-S-H can vary) Crushed stone aggregate Main article: Construction aggregate

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.

The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as pasting the surfaces of the aggregate together, and is typically the most expensive component. Thus variation in sizes of the aggregate reduces the cost of concrete.[30] The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete.

Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients.[31]

Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers.

In addition to being decorative, exposed aggregate may add robustness to a concrete.[32]

Constructing a rebar cage. This cage will be permanently embedded in poured concrete to create a reinforced concrete structure. Main article: Reinforced concrete

Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete adds either steel reinforcing bars, steel fibers, glass fibers, or plastic fibers to carry tensile loads.

Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement and are added to the concrete at the time of batching/mixing.[33] (See the section on Concrete Production, below.)The common types of admixtures[34] are as follows:

Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures),[33] or as a replacement for Portland cement (blended cements).[39] Products which incorporate limestone, fly ash, blast furnace slag, and other useful materials with pozzolanic properties into the mix, are being tested and used. This development is due to cement production being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions,[40] as well as lowering costs, improving concrete properties, and recycling wastes.

Concrete plant facility showing a Concrete mixer being filled from the ingredient silos.

Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant, or often a batch plant.

In general usage, concrete plants come in two main types, ready mix plants and central mix plants. A ready mix plant mixes all the ingredients except water, while a central mix plant mixes all the ingredients including water. A central mix plant offers more accurate control of the concrete quality through better measurements of the amount of water added, but must be placed closer to the work site where the concrete will be used, since hydration begins at the plant.

A concrete plant consists of large storage hoppers for various reactive ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense the mixed concrete, often to a concrete mixer truck.

Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms, which are containers erected in the field to give the concrete its desired shape. Concrete formwork can be prepared in several ways, such as Slip forming and Steel plate construction. Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture Precast concrete products.

A wide variety of equipment is used for processing concrete, from hand tools to heavy industrial machinery. Whichever equipment builders use, however, the objective is to produce the desired building material; ingredients must be properly mixed, placed, shaped, and retained within time constraints. Any interruption in pouring the concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches.[46] Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect the quality and nature of the product.

When initially mixed, Portland cement and water rapidly form a gel of tangled chains of interlocking crystals, and components of the gel continue to react over time. Initially the gel is fluid, which improves workability and aids in placement of the material, but as the concrete sets, the chains of crystals join into a rigid structure, counteracting the fluidity of the gel and fixing the particles of aggregate in place. During curing, the cement continues to react with the residual water in a process of hydration. In properly formulated concrete, once this curing process has terminated the product has the desired physical and chemical properties. Among the qualities typically desired, are mechanical strength, low moisture permeability, and chemical and volumetric stability.

See also: Volumetric concrete mixer and Concrete mixer

Thorough mixing is essential for the production of uniform, high-quality concrete. For this reason equipment and methods should be capable of effectively mixing concrete materials containing the largest specified aggregate to produce uniform mixtures of the lowest slump practical for the work.

Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete.[47] The paste is generally mixed in a high-speed, shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers, pigments, or silica fume. The premixed paste is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment.[48]

Decorative plate made of Nano concrete with High-Energy Mixing (HEM) Pouring and smoothing out concrete at Palisades Park in Washington DC. Main article: Concrete slump test

Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration) and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate blend with an undesirable gradation[49] can result in a very harsh mix design with a very low slump, which cannot readily be made more workable by addition of reasonable amounts of water. An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in a mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish.[50]

Workability can be measured by the concrete slump test, a simple measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively dry sample slumps very little, having a slump value of one or two inches (25 or 50 mm) out of one foot (305 mm). A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the flow table test.

Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio.[51] Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

After mixing, concrete is a fluid and can be pumped to the location where needed.

A concrete slab ponded while curing.

A common misconception is that concrete dries as it sets, but the opposite is true - damp concrete sets better than dry concrete. In other words, "hydraulic cement" needs water to become strong. Too much water is counterproductive, but too little water is deleterious. Curing allows concrete to achieve optimal strength and hardness.[52] Curing is the hydration process that occurs after the concrete has been placed. In chemical terms, curing allows calcium-silicate hydrate (C-S-H) to form. To gain strength and harden fully, concrete curing requires time. In around 4 weeks, typically over 90% of the final strength is reached, although strengthening may continue for decades.[53] The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO2 over several decades further strengthens the concrete and makes it more resistant to damage. This carbonation reaction, however, lowers the pH of the cement pore solution and can corrode the reinforcement bars.

Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.[54] Addition of short-cut polymer fibers can improve (reduce) shrinkage-induced stresses during curing and increase early and ultimate compression strength.[55]

Properly curing concrete leads to increased strength and lower permeability and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing or overheating due to the exothermic setting of cement. Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.

During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds. After the concrete is sufficiently cured, the film is allowed to abrade from the concrete through normal use.[56]

Traditional conditions for curing involve by spraying or ponding the concrete surface with water. The picture to the right shows one of many ways to achieve this, ponding – submerging setting concrete in water and wrapping in plastic to prevent dehydration. Additional common curing methods include wet burlap and plastic sheeting covering the fresh concrete.

For higher-strength applications, accelerated curing techniques may be applied to the concrete. One common technique involves heating the poured concrete with steam, which serves to both keep it damp and raise the temperature, so that the hydration process proceeds more quickly and more thoroughly.

Main article: Pervious concrete

Pervious concrete is a mix of specially graded coarse aggregate, cement, water and little-to-no fine aggregates. This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles. The hardened concrete contains interconnected air voids totalling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath. Air entrainment admixtures are often used in freeze–thaw climates to minimize the possibility of frost damage.

Two-layered pavers, top layer made of pigmented HEM Nanoconcrete.

Nanoconcrete is created by high-energy mixing (HEM) of cement, sand and water. To ensure the mixing is thorough enough to create nano-concrete, the mixer must apply a total mixing power to the mixture of 30 - 600 watts per kilogram of the mix. This mixing must continue long enough to yield a net specific energy expended upon the mix of at least 5000 joules per kilogram of the mix.[57] A plasticizer or a superplasticizer is then added to the activated mixture which can later be mixed with aggregates in a conventional concrete mixer. In the HEM process, the intense mixing of cement and water with sand provides dissipation of energy and increases shear stresses on the surface of cement particles. This intense mixing serves to divide the cement particles into extremely fine nanometer scale sizes, which provides for extremely thorough mixing. This results in the increased volume of water interacting with cement and acceleration of Calcium Silicate Hydrate (C-S-H) colloid creation.

The initial natural process of cement hydration with formation of colloidal globules about 5 nm in diameter[58] spreads into the entire volume of cement – water matrix as the energy expended upon the mix approaches and exceeds 5000 joules per kilogram.

The liquid activated high-energy mixture can be used by itself for casting small architectural details and decorative items, or foamed (expanded) for lightweight concrete. HEM Nanoconcrete hardens in low and subzero temperature conditions and possesses an increased volume of gel, which reduces capillarity in solid and porous materials.

Bacteria such as Bacillus pasteurii, Bacillus pseudofirmus, Bacillus cohnii, Sporosarcina pasteuri, and Arthrobacter crystallopoietes increase the compression strength of concrete through their biomass. Not all bacteria increase the strength of concrete significantly with their biomass.[59]:143 Bacillus sp. CT-5. can reduce corrosion of reinforcement in reinforced concrete by up to four times. Sporosarcina pasteurii reduces water and chloride permeability. B. pasteurii increases resistance to acid.[59]:146 Bacillus pasteurii and B. sphaericuscan induce calcium carbonate precipitation in the surface of cracks, adding compression strength.[59]:147

Main article: Polymer concrete

Polymer concretes are mixtures of aggregate and any of various polymers and may be reinforced. The cement is more costly than lime-based cements, but polymer concretes nevertheless have advantages, they have significant tensile strength even without reinforcement, and they are largely impervious to water. They are frequently used for repair and construction of other applications such as drains.

Concrete, when ground, can result in the creation of hazardous dust. The National Institute for Occupational Safety and Health in the United States recommends attaching local exhaust ventilation shrouds to electric concrete grinders to control the spread of this dust.[60]

Main article: Properties of concrete

Concrete has relatively high compressive strength, but much lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.

Tests can be performed to ensure that the properties of concrete correspond to specifications for the application.

Compression testing of a concrete cylinder

Different mixes of concrete ingredients produce different strengths. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.

Different strengths of concrete are used for different purposes. Very low-strength - 14 MPa (2,000 psi) or less - concrete may be used when the concrete must be lightweight.[61] Lightweight concrete is often achieved by adding air, foams, or lightweight aggregates, with the side effect that the strength is reduced. For most routine uses, 20 MPa (2,900 psi) to 32 MPa (4,600 psi) concrete is often used. 40 MPa (5,800 psi) concrete is readily commercially available as a more durable, although more expensive, option. Higher-strength concrete is often used for larger civil projects.[62] Strengths above 40 MPa (5,800 psi) are often used for specific building elements. For example, the lower floor columns of high-rise concrete buildings may use concrete of 80 MPa (11,600 psi) or more, to keep the size of the columns small. Bridges may use long beams of high-strength concrete to lower the number of spans required.[63][64] Occasionally, other structural needs may require high-strength concrete. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Strengths as high as 130 MPa (18,900 psi) have been used commercially for these reasons.[63]

The Buffalo City Court Building in Buffalo, NY.

Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction and gains strength over time. Structures made of concrete can have a long service life. Concrete is used more than any other human-made material in the world.[65] As of 2006, about 7.5 billion cubic meters of concrete are made each year, more than one cubic meter for every person on Earth.[66]

Main article: Mass concrete Aerial photo of reconstruction at Taum Sauk (Missouri) pumped storage facility in late November, 2009. After the original reservoir failed, the new reservoir was made of roller-compacted concrete.

Due to cement's exothermic chemical reaction while setting up, large concrete structures such as dams, navigation locks, large mat foundations, and large breakwaters generate excessive heat during hydration and associated expansion. To mitigate these effects post-cooling[67] is commonly applied during construction. An early example at Hoover Dam, installed a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating. Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed. Various methods also are used to pre-cool the concrete mix in mass concrete structures.[67]

Another approach to mass concrete structures that minimizes cement's thermal byproduct is the use of roller-compacted concrete, which uses a dry mix which has a much lower cooling requirement than conventional wet placement. It is deposited in thick layers as a semi-dry material then roller compacted into a dense, strong mass.

Main article: Decorative concrete Black basalt polished concrete floor

Raw concrete surfaces tend to be porous, and have a relatively uninteresting appearance. Many different finishes can be applied to improve the appearance and preserve the surface against staining, water penetration, and freezing.

Examples of improved appearance include stamped concrete where the wet concrete has a pattern impressed on the surface, to give a paved, cobbled or brick-like effect, and may be accompanied with coloration. Another popular effect for flooring and table tops is polished concrete where the concrete is polished optically flat with diamond abrasives and sealed with polymers or other sealants.

Other finishes can be achieved with chiselling, or more conventional techniques such as painting or covering it with other materials.

The proper treatment of the surface of concrete, and therefore its characteristics, is an important stage in the construction and renovation of architectural structures.[68]

40-foot cacti decorate a sound/retaining wall in Scottsdale, Arizona Main article: Prestressed concrete

Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those experienced in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. For example, a horizontal beam tends to sag. Prestressed reinforcement along the bottom of the beam counteracts this. In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.

More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days. See Brutalism.

Extreme weather conditions (extreme heat or cold; windy condition, and humidity variations) can significantly alter the quality of concrete. In cold weather concreting, many precautions are observed.[69] Low temperatures significantly slow the chemical reactions involved in hydration of cement, thus affecting the strength development. Preventing freezing is the most important precaution, as formation of ice crystals can cause damage to the crystalline structure of the hydrated cement paste. If the surface of the concrete pour is insulated from the outside temperatures, the heat of hydration will prevent freezing.

The American Concrete Institute (ACI) definition of cold weather concreting, ACI 306,[70] is:

In Canada, where temperatures tend to be much lower during the cold season, the following criteria is used by CSA A23.1:

The minimum strength before exposing concrete to extreme cold is 500 psi (3.5 MPa). CSA A 23.1 specified a compressive strength of 7.0 MPa to be considered safe for exposure to freezing.

Concrete roads are more fuel efficient to drive on,[71] more reflective and last significantly longer than other paving surfaces, yet have a much smaller market share than other paving solutions. Modern-paving methods and design practices have changed the economics of concrete paving, so that a well-designed and placed concrete pavement will be less expensive on initial costs and significantly less expensive over the life cycle. Another major benefit is that pervious concrete can be used, which eliminates the need to place storm drains near the road, and reducing the need for slightly sloped roadway to help rainwater to run off. No longer requiring discarding rainwater through use of drains also means that less electricity is needed (more pumping is otherwise needed in the water-distribution system), and no rainwater gets polluted as it no longer mixes with polluted water. Rather, it is immediately absorbed by the ground.

Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Similarly, relatively little energy is used in producing and combining the raw materials (although large amounts of CO2 are produced by the chemical reactions in cement manufacture).[72] The overall embodied energy of concrete at roughly 1 to 1.5 megajoules per kilogram is therefore lower than for most structural and construction materials.[73]

Once in place, concrete offers great energy efficiency over the lifetime of a building.[74] Concrete walls leak air far less than those made of wood frames.[75] Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs.[76] While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. Insulating concrete forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

A modern building: Boston City Hall (completed 1968) is constructed largely of concrete, both precast and poured in place. Of Brutalist architecture, it was voted "The World's Ugliest Building" in 2008.

Concrete buildings are more resistant to fire than those constructed using steel frames, since concrete has lower heat conductivity than steel and can thus last longer under the same fire conditions. Concrete is sometimes used as a fire protection for steel frames, for the same effect as above. Concrete as a fire shield, for example Fondu fyre, can also be used in extreme environments like a missile launch pad.

Options for non-combustible construction include floors, ceilings and roofs made of cast-in-place and hollow-core precast concrete. For walls, concrete masonry technology and Insulating Concrete Forms (ICFs) are additional options. ICFs are hollow blocks or panels made of fireproof insulating foam that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

Concrete also provides good resistance against externally applied forces such as high winds, hurricanes, and tornadoes owing to its lateral stiffness, which results in minimal horizontal movement. However this stiffness can work against certain types of concrete structures, particularly where a relatively higher flexing structure is required to resist more extreme forces.

As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcement, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally.[77] These risks can be reduced through seismic retrofitting of at-risk buildings, (e.g. school buildings in Istanbul, Turkey[78]).

Concrete spalling caused by the corrosion of rebar Main article: Concrete degradation

Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonatation, chlorides, sulfates and distillate water).[citation needed] The micro fungi Aspergillus Alternaria and Cladosporium were able to grow on samples of concrete used as a radioactive waste barrier in the Chernobyl reactor; leaching aluminium, iron, calcium and silicon.[79]

The Tunkhannock Viaduct began service in 1912 and is still in regular use more than 100 years later.

Concrete can be viewed as a form of artificial sedimentary rock. As a type of mineral, the compounds of which it is composed are extremely stable.[80] Many concrete structures are built with an expected lifetime of approximately 100 years,[81] but researchers have suggested that adding silica fume could extend the useful life of bridges and other concrete uses to as long as 16,000 years.[82] Coatings are also available to protect concrete from damage, and extend the useful life. Epoxy coatings may be applied only to interior surfaces, though, as they would otherwise trap moisture in the concrete.[83]

A self-healing concrete has been developed that can also last longer than conventional concrete.[84] Another option is to use hydrophobic concrete.

Concrete mixing plant in Birmingham, Alabama in 1936

Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, highways, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Concrete is used in large quantities almost everywhere mankind has a need for infrastructure. Concrete is one of the most frequently used building materials in animal houses and for manure and silage storage structures in agriculture.[85]

The amount of concrete used worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Concrete's use in the modern world is exceeded only by that of naturally occurring water.[86]

Concrete is also the basis of a large commercial industry. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $100 billion in revenue by 2015.[87] In the United States alone, concrete production is a $30-billion-per-year industry, considering only the value of the ready-mixed concrete sold each year.[88] Given the size of the concrete industry, and the fundamental way concrete is used to shape the infrastructure of the modern world, it is difficult to overstate the role this material plays today.

Main article: Environmental impact of concrete

The manufacture and use of concrete produce a wide range of environmental and social consequences. Some are harmful, some welcome, and some both, depending on circumstances.

A major component of concrete is cement, which similarly exerts environmental and social effects.[59]:142 The cement industry is one of the three primary producers of carbon dioxide, a major greenhouse gas (the other two being the energy production and transportation industries). As of 2001, the production of Portland cement contributed 7% to global anthropogenic CO2 emissions, largely due to the sintering of limestone and clay at 1,500 °C (2,730 °F).[89]

Concrete is used to create hard surfaces that contribute to surface runoff, which can cause heavy soil erosion, water pollution, and flooding, but conversely can be used to divert, dam, and control flooding.

Concrete is a contributor to the urban heat island effect, though less so than asphalt.[90]

Workers who cut, grind or polish concrete are at risk of inhaling airborne silica, which can lead to silicosis.[91] Concrete dust released by building demolition and natural disasters can be a major source of dangerous air pollution.

The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns due to toxicity and radioactivity. Fresh concrete (before curing is complete) is highly alkaline and must be handled with proper protective equipment.

Recycled crushed concrete, to be reused as granular fill, is loaded into a semi-dump truck. Main article: Concrete recycling

Concrete recycling is an increasingly common method for disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws and economic benefits.

Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks and rocks.

Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On 3 March 1983, a government-funded research team (the VIRL research.codep) estimated that almost 17% of worldwide landfill was by-products of concrete based waste.[citation needed]

The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years. The previous record was 12.3 million cubic meters held by Itaipu hydropower station in Brazil.[92][93][93][94]

The world record for concrete pumping was set on 7 August 2009 during the construction of the Parbati Hydroelectric Project, near the village of Suind, Himachal Pradesh, India, when the concrete mix was pumped through a vertical height of 715 m (2,346 ft).[95][96]

The world record for the largest continuously poured concrete raft was achieved in August 2007 in Abu Dhabi by contracting firm Al Habtoor-CCC Joint Venture and the concrete supplier is Unibeton Ready Mix.[97][98] The pour (a part of the foundation for the Abu Dhabi's Landmark Tower) was 16,000 cubic meters of concrete poured within a two-day period.[99] The previous record, 13,200 cubic meters poured in 54 hours despite a severe tropical storm requiring the site to be covered with tarpaulins to allow work to continue, was achieved in 1992 by joint Japanese and South Korean consortiums Hazama Corporation and the Samsung C&T Corporation for the construction of the Petronas Towers in Kuala Lumpur, Malaysia.[100]

The world record for largest continuously poured concrete floor was completed 8 November 1997, in Louisville, Kentucky by design-build firm EXXCEL Project Management. The monolithic placement consisted of 225,000 square feet (20,900 m2) of concrete placed within a 30-hour period, finished to a flatness tolerance of FF 54.60 and a levelness tolerance of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.[101][102]

The record for the largest continuously placed underwater concrete pour was completed 18 October 2010, in New Orleans, Louisiana by contractor C. J. Mahan Construction Company, LLC of Grove City, Ohio. The placement consisted of 10,251 cubic yards of concrete placed in a 58.5 hour period using two concrete pumps and two dedicated concrete batch plants. Upon curing, this placement allows the 50,180-square-foot (4,662 m2) cofferdam to be dewatered approximately 26 feet (7.9 m) below sea level to allow the construction of the Inner Harbor Navigation Canal Sill & Monolith Project to be completed in the dry.[103]

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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Parking Lot Sealer in Woodmead  except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Driveway Pavers Contractors is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Parking Lot Sealer Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  How To Pave A Driveway With Asphalt the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Bleeding or flushing is shiny, black surface film of asphalt on the road surface caused by upward movement of asphalt in the pavement surface.[1][2] Common causes of bleeding are too much asphalt in asphalt concrete, hot weather, low space air void content and quality of asphalt.[3]

Bleeding is a safety concern since it results in a very smooth surface, without the texture required to prevent hydroplaning.

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Crocodile cracking, also called alligator cracking and perhaps misleadingly fatigue cracking, is a common type of distress in asphalt pavement. The following is more closely related to fatigue cracking which is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile.[1] Cell sizes can vary in size up to 11.80 inches (300 mm) across, but are typically less than 5.90 inches (150 mm) across. Fatigue cracking is generally a loading failure,[1] but numerous factors can contribute to it. It is often a sign of sub-base failure, poor drainage, or repeated over-loadings. It is important to prevent fatigue cracking, and repair as soon as possible, as advanced cases can be very costly to repair and can lead to formation of potholes or premature pavement failure.

It is usually studied under the transportation section of civil engineering.

Fatigue cracking is an asphalt pavement distress most often instigated by failure of the surface due to traffic loading. However, fatigue cracking can be greatly influenced by environmental and other effects while traffic loading remains the direct cause. Frequently, overloading happens because the base or subbase inadequately support the surface layer and subsequently cannot handle loads that it would normally endure.[2] There are many ways that the subbase or base can be weakened.

Poor drainage in the road bed is a frequent cause of this degradation of the base or subgrade.[1] A heavy spring thaw, similarly to poor drainage, can weaken the base course, leading to fatigue cracking.[1]

Stripping or raveling is another possible cause of fatigue cracking. Stripping occurs when poor adhesion between asphalt and aggregate allows the aggregate at the surface to dislodge. If left uncorrected, this reduces the thickness of the pavement, reducing the affected portion's ability to carry its designed loading.[1] This can cause fatigue cracking to develop rapidly, as overloading will happen with loads of less magnitude or frequency.

Edge cracking is the formation of crescent-shaped cracks near the edge of a road.[3] It is caused by lack of support of the road edge, sometimes due to poorly drained or weak shoulders. If left untreated, additional cracks will form until it resembles fatigue cracking.[3] Like wheel-path fatigue cracking, poor drainage is a main cause of edge cracking, as it weakens the base, which hastens the deterioration of the pavement.[4] Water ponding (a buildup of water which can also be called puddling) happens more frequently near the edge than in the center of the road path, as roads are usually sloped to prevent in-lane ponding. This leads to excess moisture in the shoulders and subbase at the road edge. Edge cracking differs from fatigue cracking in that the cracks form from the top down, where fatigue cracks usually start at the bottom and propagate to the surface.

Fatigue cracking manifests itself initially as longitudinal cracking (cracks along the direction of the flow of traffic) in the top layer of the asphalt.[5] These cracks are initially thin and sparsely distributed. If further deterioration is allowed, these longitudinal cracks are connected by transverse cracks to form sharp sided, prismatic pieces. This interlaced cracking pattern resembles the scales on the back of a crocodile or alligator, hence the nickname, crocodile cracking.

More severe cases involve pumping of fines, spalling, and loose pieces of pavement. The most severe cases of fatigue cracking often occur with other pavement distresses, but are exemplified by: potholes,[1] large cracks(3/8" or larger), and severely spalled edges.[4]

There are many different ways to measure fatigue cracking, but in general a pavement distress manual or index will be used. For example, the Pavement Condition Index is widely used to quantify the overall level of distress and condition of a section of road. Measurement of fatigue cracking specifically (and pavement distress in general) is necessary to determine the overall condition of a road, and for determination of a time-line for rehabilitation and/or repair. There are many other rating systems, and many rating systems currently in use are based on the AASHO Road Test.

There are two important criteria to take into account when measuring fatigue cracking. The first is the extent of the cracking. This is the amount of road surface area which is affected by this pavement distress. The second criterion is the severity of the cracking.[6] Severity, which has been discussed above, refers to how far the cracking has progressed, and is often directly a function of crack width.[6] Severity may be rated numerically, or given a rating from "low" to "severe". The rating may be entered into a pavement management system, which will suggest a priority and method for the repair.

Systems have been developed that detect fatigue cracking and other types of pavement distress automatically.[7] They measure the severity and frequency of alligator cracking on the road-path. One such machine is the road surface profilometer, which is mounted on a vehicle and measures the profile of the road surface while it is moving down the roadway.

Preventing fatigue cracking can be as simple as preventing the common causes. For example, reducing overloading on an asphalt pavement or improving drainage[2] can prevent fatigue cracking in many cases. Prevention primarily depends on designing and constructing the pavement and subbase to support the expected traffic loads, and providing good drainage to keep water out of the subbase.

A good strategy to prevent overloading, which is a main cause of fatigue cracking, is to increase the depth of the asphalt layer. According to certain researchers, pavements that exceed a certain minimum strength or thickness can hypothetically handle infinitely many loads without showing structural defects, including fatigue cracking.[1] These pavements are called perpetual pavements or long-term performance pavements (LTPP).

When repairing pavement affected by fatigue cracking, the main cause of the distress should be determined. However, often the specific cause is fairly difficult to determine, and prevention is therefore correspondingly difficult. Any investigation should involve digging a pit or coring the pavement and subbase to determine the pavement's structural makeup as well as determining whether or not subsurface moisture is a contributing factor.[1] The repair needed also differs based on the severity and extent of the cracking.

In the early stages, sealing cracks with crack sealant limits further deterioration of the subgrade due to moisture penetration. Small areas may be repaired by removal of the affected area, and replacement with new base and asphalt surface.[2] Once the damage has progressed or the affected area is large and extensive, a structural asphalt overlay or complete reconstruction is necessary to ensure structural integrity. Proper repair may include first sealing cracks with crack sealant, installing paving fabric over a tack coat, or milling the damaged asphalt. An overlay of hot mix asphalt is then placed over the completed repair. [2]

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Driveway to a farm Driveway apron and sloped curb to a public street, all under construction

A driveway (also called drive in UK English) Driveway Sealing Companies  in Germiston is a type of private road for local access to one or a small group of structures, and is owned and maintained by an individual or group.

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Driveways rarely have traffic lights, but some that bear heavy traffic, especially those leading to commercial businesses and parks, do.

Driveways may be decorative in ways that public roads cannot, because of their lighter traffic and the willingness of owners to invest in their construction. Driveways are not resurfaced, snow blown or otherwise maintained by governments. They are generally designed to conform to the architecture of connected houses or other buildings.

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Some of the materials that can be used for driveways include concrete, decorative brick, cobblestone, block paving, asphalt, gravel, decomposed granite, and surrounded with grass or other ground-cover plants.

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Driveways are commonly used as paths to private garages, carports, or houses. On large estates, a driveway may be the road that leads to the house from the public road, possibly with a gate in between. Some driveways divide to serve different homeowners. A driveway may also refer to a small apron of pavement in front of a garage with a curb cut in the sidewalk, sometimes too short to accommodate a car.

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Often, either by choice or to conform with local regulations, cars are parked in driveways in order to leave streets clear for traffic. Moreover, some jurisdictions prohibit parking or leaving standing any motor vehicle upon any residential lawn area (defined as the property from the front of a residential house, condominium, or cooperative to the street line other than a driveway, walkway, concrete or blacktopped surface parking space).[2] Other examples include the city of Berkeley, California that forbids “any person to park or leave standing, or cause to be parked or left standing any vehicle upon any public street in the City for seventy-two or more consecutive hours.”[3] Other areas may prohibit leaving vehicles on residential streets during certain times (for instance, to accommodate regular street cleaning), necessitating the use of driveways.

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Residential driveways are also used for such things as garage sales, automobile washing and repair, and recreation, notably (in North America) for basketball practice.

Another form of driveway is a ‘Run-Up’, or short piece of land used usually at the front of the property to park a vehicle on.[citation needed]

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Residential Paving Cost Estimate Raised sidewalks beside a 2000-year-old paved road, Pompeii, Italy

A sidewalk (American English) or pavement (British English), also known as a footpath or footway, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade (height) and is normally separated from the vehicular section by a curb. There may also be a median strip or road verge (a strip of vegetation, grass or bushes or trees or a combination of these) either between the sidewalk and the roadway or between the sidewalk and the boundary.

In some places, the same term may also be used for a paved path, trail or footpath that is not next to a road, for example, a path through a park.

The term "sidewalk" is usually preferred in most of North America, along with many other countries worldwide that are not members of the Commonwealth of Nations. The term "pavement" is more common in the United Kingdom,[1] as well as parts of the Mid-Atlantic United States such as Philadelphia and New Jersey.[2][3] Many Commonwealth countries use the term "footpath". The professional, civil engineering and legal term for this in North America is "sidewalk" while in the United Kingdom it is "footway".[4]

In the United States, the term sidewalk is used for the pedestrian path beside a road. "Shared use paths" or "multi-use paths" are available for use by both pedestrians and bicyclists.[5] "Walkway" is a more comprehensive term that includes stairs, ramps, passageways, and related structures that facilitate the use of a path as well as the sidewalk.[6]

In the UK, the term "footpath" is mostly used for paths that do not abut a roadway.[7] The term "shared-use path" is used where cyclists are also able to use the same section of path as pedestrians.[8]

East India House, Leadenhall Street, London, 1766. The sidewalk is separated from the main street by six bollards in front of the building.

There is evidence that sidewalks were built in ancient times. It was claimed that the Greek city of Corinth was paved by the 4th-century, and the Romans were particularly prolific sidewalk builders – they called them semitas.[9]

However, by the Middle Ages, narrow roads had reverted to being simultaneously used by pedestrians and wagons without any formal separation between the two categories. Early attempts at ensuring the adequate maintenance of foot-ways or sidewalks were often made, such as the 1623 Act for Colchester, although they were generally not very effective.[10]

Following the Great Fire of London in 1666, attempts were slowly made to bring some order to the sprawling city. In 1671, 'Certain Orders, Rules and Directions Touching the Paving and Cleansing The Streets, Lanes and Common Passages within the City of London' were formulated, calling for all streets to be adequately paved for pedestrians with cobblestones. Purbeck stone was widely used as a durable paving material. Bollards were also installed to protect pedestrians from the traffic in the middle of the road.

A series of Paving Acts from the House of Commons during the 18th century, especially the 1766 Paving & Lighting Act, authorized the City of London Corporation to create foot-ways throughout all the streets of London, to pave them with Purbeck stone (the thoroughfare in the middle was generally cobblestone) and to raise them above the street level with curbs forming the separation.[11] The Corporation was also made responsible for the regular upkeep of the roads, including their cleaning and repair, for which they charged a tax from 1766.[12] By the late 19th-century large and spacious sidewalks were routinely constructed in European capitals, and were associated with urban sophistication.

In the United States, adjoining property owners must in most situations finance all or part of the cost of sidewalk construction. In a legal case in 1917 involving E. L. Stewart, a former member of the Louisiana House of Representatives and a lawyer in Minden in Webster Parish, the Louisiana Supreme Court ruled that owners must pay whether they wish for the sidewalk to be constructed or not.[13]

Pedestrians walking on the pavement (sidewalk) in London.

Sidewalks play an important role in transportation, as they provide a safe path for people to walk along that is separated from the motorized traffic. They aid road safety by minimizing interaction between pedestrians and motorized traffic. Sidewalks are normally in pairs, one on each side of the road, with the center section of the road for motorized vehicles.

In rural roads, sidewalks may not be present as the amount of traffic (pedestrian or motorized) may not be enough to justify separating the two. In suburban and urban areas, sidewalks are more common. In town and city centers (known as downtown in North America) the amount of pedestrian traffic can exceed motorized traffic, and in this case the sidewalks can occupy more than half of the width of the road, or the whole road can be reserved for pedestrians, see Pedestrian zone.

Sidewalks may have a small effect on reducing vehicle miles traveled and carbon dioxide emissions. A study of sidewalk and transit investments in Seattle neighborhoods found vehicle travel reductions of 6 to 8% and CO2 emission reductions of 1.3 to 2.2% [14]

Sidewalk with bike path See also: Road traffic safety

Research commissioned for the Florida Department of Transportation, published in 2005, found that, in Florida, the Crash Reduction Factor (used to estimate the expected reduction of crashes during a given period) resulting from the installation of sidewalks averaged 74%.[15] Research at the University of North Carolina for the U.S. Department of Transportation found that the presence or absence of a sidewalk and the speed limit are significant factors in the likelihood of a vehicle/pedestrian crash. Sidewalk presence had a risk ratio of 0.118, which means that the likelihood of a crash on a road with a paved sidewalk was 88.2 percent lower than one without a sidewalk. “This should not be interpreted to mean that installing sidewalks would necessarily reduce the likelihood of pedestrian/motor vehicle crashes by 88.2 percent in all situations. However, the presence of a sidewalk clearly has a strong beneficial effect of reducing the risk of a ‘walking along roadway’ pedestrian/motor vehicle crash.” The study does not count crashes that happen when walking across a roadway. The speed limit risk ratio was 1.116, which means that a 16.1-km/h (10-mi/h) increase in the limit yields a factor of (1.116)10 or 3.[16]

The presence or absence of sidewalks was one of three factors that were found to encourage drivers to choose lower, safer speeds.[17]

On the other hand, the implementation of schemes which involve the removal of sidewalks, such as shared space schemes, are reported to deliver a dramatic drop in crashes and congestion too, which indicates that a number of other factors, such as the local speed environment, also play an important role in whether sidewalks are necessarily the best local solution for pedestrian safety.[18]

In cold weather, black ice is a common problem with unsalted sidewalks. The ice forms a thin transparent surface film which is almost impossible to see, and so results in many slips by pedestrians.

Riding bicycles on sidewalks is discouraged since some research shows it to be more dangerous than riding in the street.[19] Some jurisdictions prohibit sidewalk riding except for children. In addition to the risk of cyclist/pedestrian collisions, cyclists face increase risks from collisions with motor vehicles at street crossings and driveways. Riding in the direction opposite to traffic in the adjacent lane is especially risky.[20]

Since residents of neighborhoods with sidewalks are more likely to walk, they tend to have lower rates of cardiovascular disease, obesity, and other health issues related to sedentary lifestyles.[21] Also, children who walk to school have been shown to have better concentration.[22]

Native Americans busking at Orchard Road, Singapore

Some sidewalks may be used as social spaces with sidewalk cafes, markets, or busking musicians, as well as for parking for a variety of vehicles including cars, motorbikes and bicycles.

Contemporary sidewalks are most often made of concrete in the United States and Canada, while tarmac, asphalt, brick, stone, slab and (increasingly) rubber are more common in Europe.[23] Different materials are more or less friendly environmentally: pumice-based trass, for example, when used as an extender is less energy-intensive than Portland cement concrete or petroleum-based materials such as asphalt or tar-penetration macadam). Multi-use paths alongside roads are sometimes made of materials that are softer than concrete, such as asphalt.

In the 19th century and early 20th century, sidewalks of wood were common in some North American locations. They may still be found at historic beach locations and in conservation areas to protect the land beneath and around, called boardwalks.

Brick sidewalks are found in some urban areas, usually for aesthetic purposes. Brick sidewalk construction usually involves the usage of a mechanical vibrator to lock the bricks in place after they have been laid (and/or to prepare the soil before laying). Although this might also be done by other tools (as regular hammers and heavy rolls), a vibrator is often used to speed up the process.

Stone slabs called flagstones or flags are sometimes used where an attractive appearance is required, as in historic town centers. In other places, pre-cast concrete slabs (called paving slabs or, less correctly, paving stones) are used. These may be colored or textured to resemble stone.

Freshly laid concrete sidewalk, with horizontal strain-relief grooves faintly visible

In the United States and Canada, the most common type of sidewalk consists of a poured concrete ribbon, examples of which from as early as the 1860s can be found in good repair in San Francisco, and stamped with the name of the contractor and date of installation.[citation needed] When quantities of Portland cement were first imported to the United States in the 1880s, its principal use was in the construction of sidewalks.[24]

Today, most sidewalk ribbons are constructed with cross-lying strain-relief grooves placed or sawn at regular intervals typically 5 feet (1.5 m) apart. This partitioning, an improvement over the continuous slab, was patented in 1924 by Arthur Wesley Hall and William Alexander McVay, who wished to minimize damage to the concrete from the effects of tectonic and temperature fluctuations, both of which can crack longer segments.[25] The technique is not perfect, as freeze-thaw cycles (in cold-weather regions) and tree root growth can eventually result in damage which requires repair.

In highly variable climates which undergo multiple freeze-thaw cycles, the concrete blocks will be separated by expansion joints to allow for thermal expansion without breakage. The use of expansion joints in sidewalks may not be necessary, as the concrete will shrink while setting.[26]

In the United Kingdom, Australia and France suburban sidewalks are most commonly constructed of tarmac. In urban or inner-city areas sidewalks are most commonly constructed of slabs, stone, or brick depending upon the surrounding street architecture and furniture.

Driveway Sealing Companies in Northgate

The Paving Company Near Me Thru lanes indicated by arrows on California CR G4 (Montague Expressway) in Silicon Valley.

In the context of traffic control, a lane is part of a roadway (carriageway) that is designated for use by a single line of vehicles, to control and guide drivers and reduce traffic conflicts.[1] Most public roads (highways) have at least two lanes, one for traffic in each direction, separated by lane markings. On multilane roadways and busier two-lane roads, lanes are designated with road surface markings. Major highways often have two multi-lane roadways separated by a median.

Some roads and bridges that carry very low volumes of traffic are less than 15 feet (4.6 m) wide, and are only a single lane wide. Vehicles travelling in opposite directions must slow or stop to pass each other. In rural areas, these are often called country lanes. In urban areas, alleys are often only one lane wide. Urban and suburban one lane roads are often designated for one-way traffic.

Lane capacity varies widely due to conditions such as neighboring lanes, lane width, elements next to the road, number of driveways, presence of parking, speed limits, number of heavy vehicles and so on – the range can be as low as 1000 passenger cars / hour to as high as 4800 passenger cars /hour but mostly falls between 1500 and 2400 passenger cars / hour.[2]

The Ontario Highway 401 in the Greater Toronto area, with 17 travel lanes in 6 separate carriageways visible in the midground. Turning lane on the Rodovia BR-101 (Brazil) Play media Changing lanes, Gothenburg, Sweden Transfer lanes, connecting surface collector lanes with through lanes between two tunnels A left-turn merging lane in Germany, needing explanation by a crafted sign These usages lead to the phrases life in the slow lane and life in the fast lane, used to describe relaxed or busy lifestyles, respectively and used as the titles of various books and songs.

While in general, wider lanes are associated with a reduction in crashes,[7] in urban settings both narrow (less than 2.8 m) and wide (over 3.1~3.2 m) lanes increase crash risks.[8] Wider lanes (over 3.3~3.4m) are associated with 33% higher impact speeds, as well as higher crash rates. Carrying capacity is also maximal at a width of 3 to 3.1 metres (9.8 to 10.2 ft), both for motor traffic and for bicycles. Pedestrian volume declines as lanes widen, and intersections with narrower lanes provide the highest capacity for bicycles.[9] As lane width decreases, traffic speed diminishes.[10]

Advocates for safety of people walking and people on bikes, and many new urbanists disagree with traditional thinking in traffic engineering, saying that safety and capacity are not adversely impacted by reducing lanes widths to as little as 10 feet (3.0 m).[11] Moreover, wider travel lanes also increase exposure and crossing distance for pedestrians at intersections and midblock crossings.

assumed widths and heights in road design for Europe (in meters)

The widths of vehicle lanes typically vary from 9 to 15 feet (2.7 to 4.6 m). Lane widths are commonly narrower on low volume roads and wider on higher volume roads. The lane width depends on the assumed maximum vehicle width with an additional space to allow for lateral motion of the vehicle.

The maximum truck width had been 96 inches (2.438 m) in the Code of Federal Regulations of 1956 which matches with the width of eight-foot for shipping containers. This had been increased to 102 inches (2.591 m) in 1976 which explicitly states to be read as the slightly larger metric 2.6 metres (102.36 in) width respecting international harmonization.[12] The same applies to standards in Europe which had increased the allowable size of road vehicles with a current maximum of 2.55 metres (100.39 in) for most trucks and allowing 2.6 metres (102.36 in) for refrigerator trucks. The minimum extra space had been 0.20 metres (7.87 in) and it is currently assumed to be at least 0.25 metres (9.84 in) on each side. For roads with a lower amount of traffic it is allowed to build the second or third lane in the same direction to an assumed lower width for cars like 1.75 metres (68.90 in), however this is not recommended as a design principle for new roads as changes in the amount of traffic could make for unnecessarily increased risks in the future.

The Interstate Highway standards for the U.S. Interstate Highway System uses a 12-foot (3.7 m) standard for lane width, while narrower lanes are used on lower classification roads. In Europe, as laws and road width vary by country, the minimum widths of lanes is generally between 2.5 to 3.25 metres (8.2 to 10.7 ft).[13] The federal Bundesstraße interurban network in Germany defines a minimum of 3.5 metres (11 ft 6 in) for each lane for the smallest two lane roads with an additional 0.25 metres (9.84 in) on the outer sides and shoulders being at least 1.5 metres (59.06 in) on each side. A modern Autobahn divided highway will have two lanes per direction which are 3.75 metres (12 ft 4 in) wide with an additional clearance of 0.50 metres (19.69 in) on each side, while three lanes per direction are set at 3.75 metres (12 ft 4 in) for the rightmost lane and 3.5 metres (11 ft 6 in) for the other lanes. Urban access roads and roads in low-density areas may have lanes as small as 2.75 metres (9 ft 0 in) in width per lane with shoulders being at least 1 metre (3 ft 3 in) wide.[14]

Main article: Road surface marking A typical rural American freeway (Interstate 5 in the Central Valley of California). Notice the yellow line on the left, the dashed white line in the middle, and the solid white line on the right. Also note the rumble strip to the left of the yellow line.

Painted lane markings vary widely from country to country. In the United States, Canada, Mexico, Honduras, Puerto Rico, Virgin Islands and Norway, yellow lines separate traffic going opposite directions and white separates lanes of traffic traveling the same direction, but such is not the case in many European countries.

Lane markings are mostly lines painted on the road by a road marking machine, which can adjust the marking widths according to the lane type.[15]

Traffic reports in California often refer to accidents being "in the number X lane." The California Department of Transportation (Caltrans) assigns the numbers from left to right.[16] The far left passing lane is the number 1 lane. The number of the slow lane (closest to freeway onramps/offramps) depends on the total number of lanes, and could be anywhere from 2 to 8.

For much of human history, roads did not need lane markings because most people walked or rode horses at relatively slow speeds. Another reason for not using lane markings is that they are expensive to maintain.

When automobiles, trucks, and buses came into widespread use during the first two decades of the 20th century, head-on collisions became more common.

Without the guidance provided by lane markings, drivers in the early days often erred in favor of keeping closer to the middle of the road, rather than risk going off-road into ditches or trees[citation needed]. This practice often left inadequate room for opposing traffic.

The history of lane markings is connected to the mass automobile construction in Detroit. It resulted in the formation of the first Road Commission of Wayne County, Michigan in 1906 which was trying to make roads safer (Henry Ford served on the board in the first year).[17] The commission would order the construction of the first concrete road in 1909 (the Woodard Avenue in Detroit) and it conceived the centerline for highways in 1911. Hence the chairmen of the Road Commission, Edward N. Hines is widely credited as the inventor of line markings.[18]

The introduction as a common standard is connected to June McCarroll, a physician in Indio, California who started experimenting with painting lines on roads in 1917 after she was run off a highway by a truck driver. In November 1924, after years of lobbying by Dr. McCarroll and her allies, California officially adopted a policy of painting lines on its highways. A portion of Interstate 10 near Indio has been named the Dr. June McCarroll Memorial Freeway in her honor.

black center line on an Autobahn in Germany (late 1930s)

The first lane markings in Europe were painted at an accident hotspot in the small town of Sutton Coldfield near Birmingham, England in 1921. The success of this experiment made its way to other hotspots and later standardization of white paint for line markings in Great Britain.[19]

The first lane markings in Germany were used in Berlin in 1925 using white paint for line markings and road edge markings. When the standard for the new autobahn network was conceived in the 1930s it mandated the usage of black paint for the center line for each carriageway as black was better visible on the bright surface of the concrete roads.

By 1939, lane markings had become so popular that they were officially standardized throughout the United States. The concept of line markings spread throughout the world becoming standard for most roads. Originally the lines were drawn manually with normal paint which would bleach out quickly. After the war, the first machines for line markings were invented[20] and a plastic strip was becoming standard in the 1950s which led to gradually find line markings on all roads.

Main article: Right- and left-hand traffic

Driveway

Asphalt Road Price Permeable paving demonstration Stone paving in Santarém, Portugal

Permeable paving is a method of paving vehicle and pedestrian pathways that allows for infiltration of fluids. In pavement design the base is the top portion of the roadway that pedestrians or vehicles come into contact with. The media used for the base of permeable paving may be porous to allow for fluids to flow through it or nonporous media that are spaced so that fluid may flow in between the crack may be used. In addition to reducing surface runoff, permeable paving can trap suspended solids therefore filtering pollutants from stormwater.[1] Examples include roads, paths, and parking lots that are subject to light vehicular traffic, such as cycle-paths, service or emergency access lanes, road and airport shoulders, and residential sidewalks and driveways.

Although some porous paving materials appear nearly indistinguishable from nonporous materials, their environmental effects are qualitatively different. Whether it is pervious concrete, porous asphalt, paving stones or concrete or plastic-based pavers, all these pervious materials allow stormwater to percolate and infiltrate the surface areas, traditionally impervious to the soil below. The goal is to control stormwater at the source, reduce runoff and improve water quality by filtering pollutants in the substrata layers.

Permeable solutions can be based on: porous asphalt and concrete surfaces, concrete pavers (permeable interlocking concrete paving systems – PICP), or polymer-based grass pavers, grids and geocells. Porous pavements and concrete pavers (actually the voids in-between them) enable stormwater to drain through a stone base layer for on-site infiltration and filtering. Polymer based grass grid or cellular paver systems provide load bearing reinforcement for unpaved surfaces of gravel or turf.

Grass pavers, plastic turf reinforcing grids (PTRG), and geocells (cellular confinement systems) are honeycombed 3D grid-cellular systems, made of thin-walled HDPE plastic or other polymer alloys. These provide grass reinforcement, ground stabilization and gravel retention. The 3D structure reinforces infill and transfers vertical loads from the surface, distributing them over a wider area. Selection of the type of cellular grid depends to an extent on the surface material, traffic and loads. The cellular grids are installed on a prepared base layer of open-graded stone (higher void spacing) or engineered stone (stronger). The surface layer may be compacted gravel or topsoil seeded with grass and fertilizer. In addition to load support, the cellular grid reduces compaction of the soil to maintain permeability, while the roots improve permeability due to their root channels.[2]

In new suburban growth, porous pavements protect watersheds. In existing built-up areas and towns, redevelopment and reconstruction are opportunities to implement stormwater water management practices. Permeable paving is an important component in Low Impact Development (LID), a process for land development in the United States that attempts to minimize impacts on water quality and the similar concept of sustainable drainage systems (SuDS) in the United Kingdom.

The infiltration capacity of the native soil is a key design consideration for determining the depth of base rock for stormwater storage or for whether an underdrain system is needed.

Permeable paving surfaces have been demonstrated as effective in managing runoff from paved surfaces.[3][4] Large volumes of urban runoff causes serious erosion and siltation in surface water bodies. Permeable pavers provide a solid ground surface, strong enough to take heavy loads, like large vehicles, while at the same time they allow water to filter through the surface and reach the underlying soils, mimicking natural ground absorption.[5] They can reduce downstream flooding and stream bank erosion, and maintain base flows in rivers to keep ecosystems self-sustaining. Permeable pavers also combat erosion that occurs when grass is dry or dead, by replacing grassed areas in suburban and residential environments.[6]

Permeable paving surfaces keep the pollutants in place in the soil or other material underlying the roadway, and allow water seepage to groundwater recharge while preventing the stream erosion problems. They capture the heavy metals that fall on them, preventing them from washing downstream and accumulating inadvertently in the environment. In the void spaces, naturally occurring micro-organisms digest car oils, leaving little but carbon dioxide and water. Rainwater infiltration is usually less than that of an impervious pavement with a separate stormwater management facility somewhere downstream.[citation needed].in areas where infiltration is not possible due to unsuitable soil conditions permeable pavements are used in the attenuation mode where water is retained in the pavement and slowly released to surface water systems between storm events.

Permeable pavements may give urban trees the rooting space they need to grow to full size. A "structural-soil" pavement base combines structural aggregate with soil; a porous surface admits vital air and water to the rooting zone. This integrates healthy ecology and thriving cities, with the living tree canopy above, the city's traffic on the ground, and living tree roots below. The benefits of permeables on urban tree growth have not been conclusively demonstrated and many researchers have observed tree growth is not increased if construction practices compact materials before permeable pavements are installed.[7][8]

Permeable pavements are designed to replace Effective Impervious Areas (EIAs), not to manage stormwater from other impervious surfaces on site. Use of this technique must be part of an overall on site management system for stormwater, and is not a replacement for other techniques.

Also, in a large storm event, the water table below the porous pavement can rise to a higher level preventing the precipitation from being absorbed into the ground. The additional water is stored in the open graded crushed drain rock base and remains until the subgrade can absorb the water. For clay-based soils, or other low to 'non'-draining soils, it is important to increase the depth of the crushed drain rock base to allow additional capacity for the water as it waits to be infiltrated.

The best way to prevent this problem is to understand the soil infiltration rate, and design the pavement and base depths to meet the volume of water. Or, allow for adequate rain water run off at the pavement design stage.

Highly contaminated runoff can be generated by some land uses where pollutant concentrations exceed those typically found in stormwater. These "hot spots" include commercial plant nurseries, recycling facilities, fueling stations, industrial storage, marinas, some outdoor loading facilities, public works yards, hazardous materials generators (if containers are exposed to rainfall), vehicle service and maintenance areas, and vehicle and equipment washing and steam cleaning facilities. Since porous pavement is an infiltration practice, it should not be applied at stormwater hot spots due to the potential for groundwater contamination. All contaminated runoff should be prevented from entering municipal storm drain systems by using best management practices (BMPs) for the specific industry or activity.[9]

Reference sources differ on whether low or medium traffic volumes and weights are appropriate for porous pavements. For example, around truck loading docks and areas of high commercial traffic, porous pavement is sometimes cited as being inappropriate. However, given the variability of products available, the growing number of existing installations in North America and targeted research by both manufacturers and user agencies, the range of accepted applications seems to be expanding. Some concrete paver companies have developed products specifically for industrial applications. Working examples exist at fire halls, busy retail complex parking lots, and on public and private roads, including intersections in parts of North America with quite severe winter conditions.

Permeable pavements may not be appropriate when land surrounding or draining into the pavement exceeds a 20 percent slope, where pavement is down slope from buildings or where foundations have piped drainage at their footers. The key is to ensure that drainage from other parts of a site is intercepted and dealt with separately rather than being directed onto permeable surfaces.

Cold climates may present special challenges. Road salt contains chlorides that could migrate through the porous pavement into groundwater. Snow plow blades could catch block edges and damage surfaces. Sand cannot be used for snow and ice control on perveous asphalt or concrete because it will plug the pores and reduce permeability. Infiltrating runoff may freeze below the pavement, causing frost heave, though design modifications can reduce this risk. These potential problems do not mean that porous pavement cannot be used in cold climates. Porous pavement designed to reduce frost heave has been used successfully in Norway. Furthermore, experience suggests that rapid drainage below porous surfaces increases the rate of snow melt above.

Some estimates put the cost of permeable paving at two to three times that of conventional asphalt paving. Using permeable paving, however, can reduce the cost of providing larger or more stormwater BMPs on site, and these savings should be factored into any cost analysis. In addition, the off-site environmental impact costs of not reducing on-site stormwater volumes and pollution have historically been ignored or assigned to other groups (local government parks, public works and environmental restoration budgets, fisheries losses, etc.) The City of Olympia, Washington is studying the use of pervious concrete quite closely and finding that new stormwater regulations are making it a viable alternative to storm water.

Some permeable pavements require frequent maintenance because grit or gravel can block the open pores. This is commonly done by industrial vacuums that suck up all the sediment. If maintenance is not carried out on a regular basis, the porous pavements can begin to function more like impervious surfaces. With more advanced paving systems the levels of maintenance needed can be greatly decreased, elastomerically bound glass pavements requires less maintenance than regular concrete paving as the glass bound pavement has 50% more void space.

Plastic grid systems, if selected and installed correctly, are becoming more and more popular with local government maintenance personnel owing to the reduction in maintenance efforts: reduced gravel migration and weed suppression in public park settings.

Some permeable paving products are prone to damage from misuse, such as drivers who tear up patches of plastic & gravel grid systems by "joy riding" on remote parking lots at night. The damage is not difficult to repair but can look unsightly in the meantime. Grass pavers require supplemental watering in the first year to establish the vegetation, otherwise they may need to be re-seeded. Regional climate also means that most grass applications will go dormant during the dry season. While brown vegetation is only a matter of aesthetics, it can influence public support for this type of permeable paving.

Traditional permeable concrete paving bricks tend to lose their color in relatively short time which can be costly to replace or clean and is mainly due to the problem of efflorescence.

Efflorescence is a hardened crystalline deposit of salts, which migrate from the center of concrete or masonry pavers to the surface to form insoluble calcium carbonates that harden on the surface. Given time, these deposits form much like how a stalactite takes shape in a cave, except in this case on a flat surface. Efflorescence usually appears white, gray or black depending on the region.

Over time efflorescence begins to negatively affect the overall appearance of masonry/concrete and may cause the surfaces to become slippery when exposed to moisture. If left unchecked, this efflorescence will harden whereby the calcium/lime deposits begin to affect the integrity of the cementatious surface by slowly eroding away the cement paste and aggregate. In some cases it will also discolor stained or coated surfaces.

Efflorescence forms more quickly in areas that are exposed to excessive amounts of moisture such as near pool decks, spas, and fountains or where irrigation runoff is present. As a result, these affected regions become very slick when wet thereby causing a significant loss of "friction coefficient". This can be of serious concern especially as a public safety issue to individuals, principals and property owners by exposing them to possible injury and increased general liability claims.

Efflorescence remover chemicals can be used to remove calcium/lime build-up without damaging the integrity of the paving surface.

Installation of porous pavements is no more difficult than that of dense pavements, but has different specifications and procedures which must be strictly adhered to. Nine different families of porous paving materials present distinctive advantages and disadvantages for specific applications. Here are examples:

Main article: Pervious concrete

Pervious concrete is widely available, can bear frequent traffic, and is universally accessible. Pervious concrete quality depends on the installer's knowledge and experience.[10]

Plastic grids allow for a 100% porous system using structural grid systems for containing and stabilizing either gravel or turf. These grids come in a variety of shapes and sizes depending on use; from pathways to commercial parking lots. These systems have been used readily in Europe for over a decade, but are gaining popularity in North America due to requirements by government for many projects to meet LEED environmental building standards. Plastic grid system are also popular with homeowners due to their lower cost to install, ease of installation, and versatility. The ideal design for this type of grid system is a closed cell system, which prevents gravel/sand/turf from migrating laterally.[citation needed] It is also known as Grass pavers / Turf Pavers in India [11]

Porous asphalt is produced and placed using the same methods as conventional asphalt concrete; it differs in that fine (small) aggregates are omitted from the asphalt mixture. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. To ensure pavement strength, fiber may be added to the mix or a polymer-modified asphalt binder may be used.[12] Generally, porous asphalt pavements are designed with a subsurface reservoir that holds water that passes through the pavement, allowing it to evaporate and/or percolate slowly into the surround soils.[13][14]

Open-graded friction courses (OGFC) are a porous asphalt surface course used on highways to improve driving safety by removing water from the surface. Unlike a full-depth porous asphalt pavement, OGFCs do not drain water to the base of a pavement. Instead, they allow water to infiltrate the top 3/4 to 1.5 inch of the pavement and then drain out to the side of the roadway. This can improve the friction characteristics of the road and reducing road spray.[15]

Single-sized aggregate without any binder, e.g. loose gravel, stone-chippings, is another alternative. Although it can only be safely used in very low-speed, low-traffic settings, e.g. car-parks and drives, its potential cumulative area is great.[citation needed]

Grass pavement

Porous turf, if properly constructed, can be used for occasional parking like that at churches and stadia. Plastic turf reinforcing grids can be used to support the increased load.[16]:2 [17] Living turf transpires water, actively counteracting the "heat island" with what appears to be a green open lawn.

Main article: interlocking concrete pavers

Permeable interlocking concrete pavements are concrete units with open, permeable spaces between the units.[16]:2 They give an architectural appearance, and can bear both light and heavy traffic, particularly interlocking concrete pavers, excepting high-volume or high-speed roads.[18] Some products are polymer-coated and have an entirely porous face.

Permeable clay brick pavements are fired clay brick units with open, permeable spaces between the units. Clay pavers provide a durable surface that allows stormwater runoff to permeate through the joints.

Main article: Resin bound paving

Resin bound paving is a mixture of resin binder and aggregate. Clear resin is used to fully coat each aggregate particle before laying. Enough resin is used to allow each aggregate particle to adhere to one another and to the base yet leave voids for water to permeate through. Resin bound paving provides a strong and durable surface that is suitable for pedestrian and vehicular traffic in applications such as pathways, driveways, car parks and access roads.

Elastomerically bound recycled glass porous pavement consisting of bonding processed post consumer glass with a mixture of resins, pigments, granite and binding agents. Approximately 75 percent of glass in the U.S. is disposed in landfills.[19][20]

Stormwater management practices related to roadways:


Asphalt Surfacing Company Price

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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Driveway Paving Companies in Brakpan except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Asphalt Driveway Resurfacing is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

Asphalt concrete

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Driveway Paving Companies Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Asphalt Driveway Near Me the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

Road surface

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

Permeable paving

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Asphalt Repair Costs Permeable paving demonstration Stone paving in Santarém, Portugal

Permeable paving is a method of paving vehicle and pedestrian pathways that allows for infiltration of fluids. In pavement design the base is the top portion of the roadway that pedestrians or vehicles come into contact with. The media used for the base of permeable paving may be porous to allow for fluids to flow through it or nonporous media that are spaced so that fluid may flow in between the crack may be used. In addition to reducing surface runoff, permeable paving can trap suspended solids therefore filtering pollutants from stormwater.[1] Examples include roads, paths, and parking lots that are subject to light vehicular traffic, such as cycle-paths, service or emergency access lanes, road and airport shoulders, and residential sidewalks and driveways.

Although some porous paving materials appear nearly indistinguishable from nonporous materials, their environmental effects are qualitatively different. Whether it is pervious concrete, porous asphalt, paving stones or concrete or plastic-based pavers, all these pervious materials allow stormwater to percolate and infiltrate the surface areas, traditionally impervious to the soil below. The goal is to control stormwater at the source, reduce runoff and improve water quality by filtering pollutants in the substrata layers.

Permeable solutions can be based on: porous asphalt and concrete surfaces, concrete pavers (permeable interlocking concrete paving systems – PICP), or polymer-based grass pavers, grids and geocells. Porous pavements and concrete pavers (actually the voids in-between them) enable stormwater to drain through a stone base layer for on-site infiltration and filtering. Polymer based grass grid or cellular paver systems provide load bearing reinforcement for unpaved surfaces of gravel or turf.

Grass pavers, plastic turf reinforcing grids (PTRG), and geocells (cellular confinement systems) are honeycombed 3D grid-cellular systems, made of thin-walled HDPE plastic or other polymer alloys. These provide grass reinforcement, ground stabilization and gravel retention. The 3D structure reinforces infill and transfers vertical loads from the surface, distributing them over a wider area. Selection of the type of cellular grid depends to an extent on the surface material, traffic and loads. The cellular grids are installed on a prepared base layer of open-graded stone (higher void spacing) or engineered stone (stronger). The surface layer may be compacted gravel or topsoil seeded with grass and fertilizer. In addition to load support, the cellular grid reduces compaction of the soil to maintain permeability, while the roots improve permeability due to their root channels.[2]

In new suburban growth, porous pavements protect watersheds. In existing built-up areas and towns, redevelopment and reconstruction are opportunities to implement stormwater water management practices. Permeable paving is an important component in Low Impact Development (LID), a process for land development in the United States that attempts to minimize impacts on water quality and the similar concept of sustainable drainage systems (SuDS) in the United Kingdom.

The infiltration capacity of the native soil is a key design consideration for determining the depth of base rock for stormwater storage or for whether an underdrain system is needed.

Permeable paving surfaces have been demonstrated as effective in managing runoff from paved surfaces.[3][4] Large volumes of urban runoff causes serious erosion and siltation in surface water bodies. Permeable pavers provide a solid ground surface, strong enough to take heavy loads, like large vehicles, while at the same time they allow water to filter through the surface and reach the underlying soils, mimicking natural ground absorption.[5] They can reduce downstream flooding and stream bank erosion, and maintain base flows in rivers to keep ecosystems self-sustaining. Permeable pavers also combat erosion that occurs when grass is dry or dead, by replacing grassed areas in suburban and residential environments.[6]

Permeable paving surfaces keep the pollutants in place in the soil or other material underlying the roadway, and allow water seepage to groundwater recharge while preventing the stream erosion problems. They capture the heavy metals that fall on them, preventing them from washing downstream and accumulating inadvertently in the environment. In the void spaces, naturally occurring micro-organisms digest car oils, leaving little but carbon dioxide and water. Rainwater infiltration is usually less than that of an impervious pavement with a separate stormwater management facility somewhere downstream.[citation needed].in areas where infiltration is not possible due to unsuitable soil conditions permeable pavements are used in the attenuation mode where water is retained in the pavement and slowly released to surface water systems between storm events.

Permeable pavements may give urban trees the rooting space they need to grow to full size. A "structural-soil" pavement base combines structural aggregate with soil; a porous surface admits vital air and water to the rooting zone. This integrates healthy ecology and thriving cities, with the living tree canopy above, the city's traffic on the ground, and living tree roots below. The benefits of permeables on urban tree growth have not been conclusively demonstrated and many researchers have observed tree growth is not increased if construction practices compact materials before permeable pavements are installed.[7][8]

Permeable pavements are designed to replace Effective Impervious Areas (EIAs), not to manage stormwater from other impervious surfaces on site. Use of this technique must be part of an overall on site management system for stormwater, and is not a replacement for other techniques.

Also, in a large storm event, the water table below the porous pavement can rise to a higher level preventing the precipitation from being absorbed into the ground. The additional water is stored in the open graded crushed drain rock base and remains until the subgrade can absorb the water. For clay-based soils, or other low to 'non'-draining soils, it is important to increase the depth of the crushed drain rock base to allow additional capacity for the water as it waits to be infiltrated.

The best way to prevent this problem is to understand the soil infiltration rate, and design the pavement and base depths to meet the volume of water. Or, allow for adequate rain water run off at the pavement design stage.

Highly contaminated runoff can be generated by some land uses where pollutant concentrations exceed those typically found in stormwater. These "hot spots" include commercial plant nurseries, recycling facilities, fueling stations, industrial storage, marinas, some outdoor loading facilities, public works yards, hazardous materials generators (if containers are exposed to rainfall), vehicle service and maintenance areas, and vehicle and equipment washing and steam cleaning facilities. Since porous pavement is an infiltration practice, it should not be applied at stormwater hot spots due to the potential for groundwater contamination. All contaminated runoff should be prevented from entering municipal storm drain systems by using best management practices (BMPs) for the specific industry or activity.[9]

Reference sources differ on whether low or medium traffic volumes and weights are appropriate for porous pavements. For example, around truck loading docks and areas of high commercial traffic, porous pavement is sometimes cited as being inappropriate. However, given the variability of products available, the growing number of existing installations in North America and targeted research by both manufacturers and user agencies, the range of accepted applications seems to be expanding. Some concrete paver companies have developed products specifically for industrial applications. Working examples exist at fire halls, busy retail complex parking lots, and on public and private roads, including intersections in parts of North America with quite severe winter conditions.

Permeable pavements may not be appropriate when land surrounding or draining into the pavement exceeds a 20 percent slope, where pavement is down slope from buildings or where foundations have piped drainage at their footers. The key is to ensure that drainage from other parts of a site is intercepted and dealt with separately rather than being directed onto permeable surfaces.

Cold climates may present special challenges. Road salt contains chlorides that could migrate through the porous pavement into groundwater. Snow plow blades could catch block edges and damage surfaces. Sand cannot be used for snow and ice control on perveous asphalt or concrete because it will plug the pores and reduce permeability. Infiltrating runoff may freeze below the pavement, causing frost heave, though design modifications can reduce this risk. These potential problems do not mean that porous pavement cannot be used in cold climates. Porous pavement designed to reduce frost heave has been used successfully in Norway. Furthermore, experience suggests that rapid drainage below porous surfaces increases the rate of snow melt above.

Some estimates put the cost of permeable paving at two to three times that of conventional asphalt paving. Using permeable paving, however, can reduce the cost of providing larger or more stormwater BMPs on site, and these savings should be factored into any cost analysis. In addition, the off-site environmental impact costs of not reducing on-site stormwater volumes and pollution have historically been ignored or assigned to other groups (local government parks, public works and environmental restoration budgets, fisheries losses, etc.) The City of Olympia, Washington is studying the use of pervious concrete quite closely and finding that new stormwater regulations are making it a viable alternative to storm water.

Some permeable pavements require frequent maintenance because grit or gravel can block the open pores. This is commonly done by industrial vacuums that suck up all the sediment. If maintenance is not carried out on a regular basis, the porous pavements can begin to function more like impervious surfaces. With more advanced paving systems the levels of maintenance needed can be greatly decreased, elastomerically bound glass pavements requires less maintenance than regular concrete paving as the glass bound pavement has 50% more void space.

Plastic grid systems, if selected and installed correctly, are becoming more and more popular with local government maintenance personnel owing to the reduction in maintenance efforts: reduced gravel migration and weed suppression in public park settings.

Some permeable paving products are prone to damage from misuse, such as drivers who tear up patches of plastic & gravel grid systems by "joy riding" on remote parking lots at night. The damage is not difficult to repair but can look unsightly in the meantime. Grass pavers require supplemental watering in the first year to establish the vegetation, otherwise they may need to be re-seeded. Regional climate also means that most grass applications will go dormant during the dry season. While brown vegetation is only a matter of aesthetics, it can influence public support for this type of permeable paving.

Traditional permeable concrete paving bricks tend to lose their color in relatively short time which can be costly to replace or clean and is mainly due to the problem of efflorescence.

Efflorescence is a hardened crystalline deposit of salts, which migrate from the center of concrete or masonry pavers to the surface to form insoluble calcium carbonates that harden on the surface. Given time, these deposits form much like how a stalactite takes shape in a cave, except in this case on a flat surface. Efflorescence usually appears white, gray or black depending on the region.

Over time efflorescence begins to negatively affect the overall appearance of masonry/concrete and may cause the surfaces to become slippery when exposed to moisture. If left unchecked, this efflorescence will harden whereby the calcium/lime deposits begin to affect the integrity of the cementatious surface by slowly eroding away the cement paste and aggregate. In some cases it will also discolor stained or coated surfaces.

Efflorescence forms more quickly in areas that are exposed to excessive amounts of moisture such as near pool decks, spas, and fountains or where irrigation runoff is present. As a result, these affected regions become very slick when wet thereby causing a significant loss of "friction coefficient". This can be of serious concern especially as a public safety issue to individuals, principals and property owners by exposing them to possible injury and increased general liability claims.

Efflorescence remover chemicals can be used to remove calcium/lime build-up without damaging the integrity of the paving surface.

Installation of porous pavements is no more difficult than that of dense pavements, but has different specifications and procedures which must be strictly adhered to. Nine different families of porous paving materials present distinctive advantages and disadvantages for specific applications. Here are examples:

Main article: Pervious concrete

Pervious concrete is widely available, can bear frequent traffic, and is universally accessible. Pervious concrete quality depends on the installer's knowledge and experience.[10]

Plastic grids allow for a 100% porous system using structural grid systems for containing and stabilizing either gravel or turf. These grids come in a variety of shapes and sizes depending on use; from pathways to commercial parking lots. These systems have been used readily in Europe for over a decade, but are gaining popularity in North America due to requirements by government for many projects to meet LEED environmental building standards. Plastic grid system are also popular with homeowners due to their lower cost to install, ease of installation, and versatility. The ideal design for this type of grid system is a closed cell system, which prevents gravel/sand/turf from migrating laterally.[citation needed] It is also known as Grass pavers / Turf Pavers in India [11]

Porous asphalt is produced and placed using the same methods as conventional asphalt concrete; it differs in that fine (small) aggregates are omitted from the asphalt mixture. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. To ensure pavement strength, fiber may be added to the mix or a polymer-modified asphalt binder may be used.[12] Generally, porous asphalt pavements are designed with a subsurface reservoir that holds water that passes through the pavement, allowing it to evaporate and/or percolate slowly into the surround soils.[13][14]

Open-graded friction courses (OGFC) are a porous asphalt surface course used on highways to improve driving safety by removing water from the surface. Unlike a full-depth porous asphalt pavement, OGFCs do not drain water to the base of a pavement. Instead, they allow water to infiltrate the top 3/4 to 1.5 inch of the pavement and then drain out to the side of the roadway. This can improve the friction characteristics of the road and reducing road spray.[15]

Single-sized aggregate without any binder, e.g. loose gravel, stone-chippings, is another alternative. Although it can only be safely used in very low-speed, low-traffic settings, e.g. car-parks and drives, its potential cumulative area is great.[citation needed]

Grass pavement

Porous turf, if properly constructed, can be used for occasional parking like that at churches and stadia. Plastic turf reinforcing grids can be used to support the increased load.[16]:2 [17] Living turf transpires water, actively counteracting the "heat island" with what appears to be a green open lawn.

Main article: interlocking concrete pavers

Permeable interlocking concrete pavements are concrete units with open, permeable spaces between the units.[16]:2 They give an architectural appearance, and can bear both light and heavy traffic, particularly interlocking concrete pavers, excepting high-volume or high-speed roads.[18] Some products are polymer-coated and have an entirely porous face.

Permeable clay brick pavements are fired clay brick units with open, permeable spaces between the units. Clay pavers provide a durable surface that allows stormwater runoff to permeate through the joints.

Main article: Resin bound paving

Resin bound paving is a mixture of resin binder and aggregate. Clear resin is used to fully coat each aggregate particle before laying. Enough resin is used to allow each aggregate particle to adhere to one another and to the base yet leave voids for water to permeate through. Resin bound paving provides a strong and durable surface that is suitable for pedestrian and vehicular traffic in applications such as pathways, driveways, car parks and access roads.

Elastomerically bound recycled glass porous pavement consisting of bonding processed post consumer glass with a mixture of resins, pigments, granite and binding agents. Approximately 75 percent of glass in the U.S. is disposed in landfills.[19][20]

Stormwater management practices related to roadways:


Asphalt concrete

Residential Paving Companies Costs Asphalt batch mix plant A machine laying asphalt concrete, fed from a dump truck

Asphalt concrete (commonly called asphalt,[1] blacktop, or pavement in North America, and tarmac or bitumen macadam or rolled asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, as well as the core of embankment dams.[2] It consists of mineral aggregate bound together with asphalt, laid in layers, and compacted. The process was refined and enhanced by Belgian inventor and U.S. immigrant Edward de Smedt.[3]

The terms asphalt (or asphaltic) concrete, bituminous asphalt concrete, and bituminous mixture are typically used only in engineering and construction documents, which define concrete as any composite material composed of mineral aggregate adhered with a binder. The abbreviation, AC, is sometimes used for asphalt concrete but can also denote asphalt content or asphalt cement, referring to the liquid asphalt portion of the composite material.

As shown in this cross-section, many older roadways are smoothed by applying a thin layer of asphalt concrete to the existing portland cement concrete, creating a composite pavement.

Mixing of asphalt and aggregate is accomplished in one of several ways:[4]

Hot-mix asphalt concrete (commonly abbreviated as HMA) This is produced by heating the asphalt binder to decrease its viscosity, and drying the aggregate to remove moisture from it prior to mixing. Mixing is generally performed with the aggregate at about 300 °F (roughly 150 °C) for virgin asphalt and 330 °F (166 °C) for polymer modified asphalt, and the asphalt cement at 200 °F (95 °C). Paving and compaction must be performed while the asphalt is sufficiently hot. In many countries paving is restricted to summer months because in winter the compacted base will cool the asphalt too much before it is able to be packed to the required density. HMA is the form of asphalt concrete most commonly used on high traffic pavements such as those on major highways, racetracks and airfields. It is also used as an environmental liner for landfills, reservoirs, and fish hatchery ponds.[5] Asphaltic concrete laying machine in operation in Laredo, Texas Warm-mix asphalt concrete (commonly abbreviated as WMA) This is produced by adding either zeolites, waxes, asphalt emulsions, or sometimes even water to the asphalt binder prior to mixing. This allows significantly lower mixing and laying temperatures and results in lower consumption of fossil fuels, thus releasing less carbon dioxide, aerosols and vapors. Not only are working conditions improved, but the lower laying-temperature also leads to more rapid availability of the surface for use, which is important for construction sites with critical time schedules. The usage of these additives in hot mixed asphalt (above) may afford easier compaction and allow cold weather paving or longer hauls. Use of warm mix is rapidly expanding. A survey of US asphalt producers found that nearly 25% of asphalt produced in 2012 was warm mix, a 416% increase since 2009.[6] Cold-mix asphalt concrete This is produced by emulsifying the asphalt in water with (essentially) soap prior to mixing with the aggregate. While in its emulsified state the asphalt is less viscous and the mixture is easy to work and compact. The emulsion will break after enough water evaporates and the cold mix will, ideally, take on the properties of an HMA pavement. Cold mix is commonly used as a patching material and on lesser trafficked service roads. Cut-back asphalt concrete Is a form of cold mix asphalt produced by dissolving the binder in kerosene or another lighter fraction of petroleum prior to mixing with the aggregate. While in its dissolved state the asphalt is less viscous and the mix is easy to work and compact. After the mix is laid down the lighter fraction evaporates. Because of concerns with pollution from the volatile organic compounds in the lighter fraction, cut-back asphalt has been largely replaced by asphalt emulsion.[7] Mastic asphalt concrete, or sheet asphalt This is produced by heating hard grade blown bitumen (i.e., partly oxidised) in a green cooker (mixer) until it has become a viscous liquid after which the aggregate mix is then added. The bitumen aggregate mixture is cooked (matured) for around 6–8 hours and once it is ready the mastic asphalt mixer is transported to the work site where experienced layers empty the mixer and either machine or hand lay the mastic asphalt contents on to the road. Mastic asphalt concrete is generally laid to a thickness of around ​3⁄4–1 ​3⁄16 inches (20–30 mm) for footpath and road applications and around ​3⁄8 of an inch (10 mm) for flooring or roof applications. High-modulus asphalt concrete, sometimes referred to by the French-language acronym EMÉ (enrobé à module élevé) This uses a very hard bituminous (penetration 10/20), sometimes modified, in proportions close to 6% on the weight of the aggregates, and a proportion of mineral powder also high, between 8–10%, to create an asphalt concrete layer with a high modulus of elasticity, of the order of 13000 MPa, as well as very high fatigue strengths.[8] High-modulus asphalt layers are used both in reinforcement operations and in the construction of new reinforcements for medium and heavy traffic. In base layers, they tend to exhibit a greater capacity of absorbing tensions and, in general, better fatigue resistance.[9]

In addition to the asphalt and aggregate, additives, such as polymers, and antistripping agents may be added to improve the properties of the final product.

Asphalt concrete pavements—especially those at airfields—are sometimes called tarmac for historical reasons, although they do not contain tar and are not constructed using the macadam process.

A variety of specialty asphalt concrete mixtures have been developed to meet specific needs, such as stone-matrix asphalt, which is designed to ensure a very strong wearing surface, or porous asphalt pavements, which are permeable and allow water to drain through the pavement for controlling stormwater.

An airport taxiway, one of the uses of asphalt concrete

Different types of asphalt concrete have different performance characteristics in terms of surface durability, tire wear, braking efficiency and roadway noise. In principle, the determination of appropriate asphalt performance characteristics must take into account the volume of traffic in each vehicle category, and the performance requirements of the friction course. Asphalt concrete generates less roadway noise than a Portland cement concrete surface, and is typically less noisy than chip seal surfaces.[10][11]

Because tire noise is generated through the conversion of kinetic energy to sound waves, more noise is produced as the speed of a vehicle increases. The notion that highway design might take into account acoustical engineering considerations, including the selection of the type of surface paving, arose in the early 1970s.[12][13] With regard to structural performance, the asphalt behaviour depends on a variety of factors including the material, loading and environmental condition. Furthermore, the performance of pavement varies over time. Therefore, the long-term behaviour of asphalt pavement is different from its short-term performance. The LTPP is a research program by the FHWA, which is specifically focusing on long-term pavement behaviour.[14][15]

Asphalt damaged by frost heaves

Asphalt deterioration can include crocodile cracking, potholes, upheaval, raveling, bleeding, rutting, shoving, stripping, and grade depressions. In cold climates, frost heaves can crack asphalt even in one winter. Filling the cracks with bitumen is a temporary fix, but only proper compaction and drainage can slow this process.

Factors that cause asphalt concrete to deteriorate over time mostly fall into one of three categories: construction quality, environmental considerations, and traffic loads. Often, damage results from combinations of factors in all three categories.

Construction quality is critical to pavement performance. This includes the construction of utility trenches and appurtenances that are placed in the pavement after construction. Lack of compaction in the surface of the asphalt, especially on the longitudinal joint can reduce the life of a pavement by 30 to 40%. Service trenches in pavements after construction have been said to reduce the life of the pavement by 50%, mainly due to the lack of compaction in the trench, and also because of water intrusion through improperly sealed joints.

Environmental factors include heat and cold, the presence of water in the subbase or subgrade soil underlying the pavement, and frost heaves.

High temperatures soften the asphalt binder, allowing heavy tire loads to deform the pavement into ruts. Paradoxically, high heat and strong sunlight also cause the asphalt to oxidize, becoming stiffer and less resilient, leading to crack formation. Cold temperatures can cause cracks as the asphalt contracts. Cold asphalt is also less resilient and more vulnerable to cracking.

Water trapped under the pavement softens the subbase and subgrade, making the road more vulnerable to traffic loads. Water under the road freezes and expands in cold weather, causing and enlarging cracks. In spring thaw, the ground thaws from the top down, so water is trapped between the pavement above and the still-frozen soil underneath. This layer of saturated soil provides little support for the road above, leading to the formation of potholes. This is more of a problem for silty or clay soils than sandy or gravelly soils. Some jurisdictions pass frost laws to reduce the allowable weight of trucks during the spring thaw season and protect their roads.

The damage a vehicle causes is proportional to the axle load raised to the fourth power,[16] so doubling the weight an axle carries actually causes 16 times as much damage. Wheels cause the road to flex slightly, resulting in fatigue cracking, which often leads to crocodile cracking. Vehicle speed also plays a role. Slowly moving vehicles stress the road over a longer period of time, increasing ruts, cracking, and corrugations in the asphalt pavement.

Other causes of damage include heat damage from vehicle fires, or solvent action from chemical spills.

The life of a road can be prolonged through good design, construction and maintenance practices. During design, engineers measure the traffic on a road, paying special attention to the number and types of trucks. They also evaluate the subsoil to see how much load it can withstand. The pavement and subbase thicknesses are designed to withstand the wheel loads. Sometimes, geogrids are used to reinforce the subbase and further strengthen the roads. Drainage, including ditches, storm drains and underdrains are used to remove water from the roadbed, preventing it from weakening the subbase and subsoil.

Good maintenance practices center on keeping water out of the pavement, subbase and subsoil. Maintaining and cleaning ditches and storm drains will extend the life of the road at low cost. Sealing small cracks with bituminous crack sealer prevents water from enlarging cracks through frost weathering, or percolating down to the subbase and softening it.

For somewhat more distressed roads, a chip seal or similar surface treatment may be applied. As the number, width and length of cracks increases, more intensive repairs are needed. In order of generally increasing expense, these include thin asphalt overlays, multicourse overlays, grinding off the top course and overlaying, in-place recycling, or full-depth reconstruction of the roadway.

It is far less expensive to keep a road in good condition than it is to repair it once it has deteriorated. This is why some agencies place the priority on preventive maintenance of roads in good condition, rather than reconstructing roads in poor condition. Poor roads are upgraded as resources and budget allow. In terms of lifetime cost and long term pavement conditions, this will result in better system performance. Agencies that concentrate on restoring their bad roads often find that by the time they've repaired them all, the roads that were in good condition have deteriorated.[17]

Some agencies use a pavement management system to help prioritize maintenance and repairs.

A small-scale asphalt recycler

Asphalt concrete is 100% recyclable and is the most widely reused construction material in the world. Very little asphalt concrete — less than 1 percent, according to a 2011 survey by the Federal Highway Administration and the National Asphalt Pavement Association — is actually disposed of in landfills.[18]

There is asphalt recycling on a large scale (known as in-place asphalt recycling or asphalt recycling performed at a hot mix plant) and asphalt recycling on a smaller scale. For small scale asphalt recycling, the user separates asphalt material into three different categories:

Blacktop cookies Chunks of virgin uncompacted hot mix asphalt which can be used for pothole repair. The use of blacktop cookies has been investigated as a less expensive, less labor-intensive, more durable alternative to repairing potholes with cold patch. In a program in Pittsfield, Massachusetts, workers purchased new hot mix asphalt and spread it liberally on the ground to produce approximately 25 lb. wafers. Once cooled, the wafers could be stored until reheated in a hotbox to make minor road repairs. Blacktop cookies may also be produced from leftover material from paving jobs.[19] Reclaimed asphalt pavement (RAP) Chunks of asphalt that have been removed from a road, parking lot or driveway are considered RAP. These chunks of asphalt typically are ripped up when making a routine asphalt repair, man hole repair, catch basin repair or sewer main repair. Because the asphalt has been compacted, RAP is a denser asphalt material and typically takes longer to recycle than blacktop cookies. Asphalt millings Small pieces of asphalt produced by mechanically grinding asphalt surfaces are referred to as asphalt millings. Large millings that have a rich, black tint indicating a high asphalt cement content are best for asphalt recycling purposes. Surface millings are recommended over full depth millings when choosing asphalt millings to recycle. Full depth millings usually contain sub-base contaminants such as gravel, mud and sand. These sub base contaminants will leach oil away from original asphalt and dry out the material in the recycling process. Asphalt milled from asphalt is better than asphalt milled from concrete. When milling asphalt from concrete the dust that is created is not compatible with asphalt products because it is not asphalt.[20]

Small scale asphalt recycling will usually involve high speed on-site asphalt recycling equipment or overnight soft heat asphalt recycling.

Small scale asphalt recycling is used when wanting to make smaller road repairs vs. large scale asphalt recycling which is done for making new asphalt or for tearing up old asphalt and simultaneously recycling / replacing existing asphalt. Recycled asphalt is very effective for pothole and utility cut repairs. The recycled asphalt will generally last as long or longer than the road around it as new asphalt cement has been added back to the material.[21]

For larger scale asphalt recycling, several in-place recycling techniques have been developed to rejuvenate oxidized binders and remove cracking, although the recycled material is generally not very water-tight or smooth and should be overlaid with a new layer of asphalt concrete. Cold in-place recycling mills off the top layers of asphalt concrete and mixes the resulting loose millings with asphalt emulsion. The mixture is then placed back down on the roadway and compacted. The water in the emulsion is allowed to evaporate for a week or so, and new hot-mix asphalt is laid on top.

Asphalt concrete that is removed from a pavement is usually stockpiled for later use as aggregate for new hot mix asphalt at an asphalt plant. This reclaimed material, or RAP, is crushed to a consistent gradation and added to the HMA mixing process. Sometimes waste materials, such as asphalt roofing shingles, crushed glass, or rubber from old tires, are added to asphalt concrete as is the case with rubberized asphalt, but there is a concern that the hybrid material may not be recyclable.

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For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Asphalt Driveway Company in Bryanston except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Asphalt Driveway Sealing Companies is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Asphalt Driveway Company Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Black Asphalt Driveway the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Diverging diamond interchange

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

Road surface

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

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The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

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Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

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Asphalt Construction Quotes Not to be confused with cement or mortar (masonry). Exterior of the Roman Pantheon, finished 128 AD, the largest unreinforced concrete dome in the world.[1] Interior of the Pantheon dome, seen from beneath. The concrete for the coffered dome was laid on moulds, probably mounted on temporary scaffolding. Opus caementicium exposed in a characteristic Roman arch. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone.

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time. Most concretes used are lime-based concretes such as Portland cement concrete or concretes made with other hydraulic cements, such as calcium aluminate cements. However, asphalt concrete, which is frequently used for road surfaces, is also a type of concrete, where the cement material is bitumen, and polymer concretes are sometimes used where the cementing material is a polymer.

When aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses.[2] Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.

Famous concrete structures include the Hoover Dam, the Panama Canal, and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, and concrete was widely used in the Roman Empire. The Colosseum in Rome was built largely of concrete, and the concrete dome of the Pantheon is the world's largest unreinforced concrete dome.[3] Today, large concrete structures (for example, dams and multi-storey car parks) are usually made with reinforced concrete.

After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Today, concrete is the most widely used human-made material (measured by tonnage).[citation needed]

The word concrete comes from the Latin word "concretus" (meaning compact or condensed),[4] the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Small-scale usage of concrete has been documented to be thousands of years old. Concrete-like materials were used since 6500 BC by the Nabataea traders or Bedouins, who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan. They discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. They kept the cisterns secret as these enabled the Nabataea to thrive in the desert.[5] Some of these structures survive to this day.[5]

In the Ancient Egyptian and later Roman eras, builders re-discovered that adding volcanic ash to the mix allowed it to set underwater.

German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400–1200 BC.[6][7] Lime mortars were used in Greece, Crete, and Cyprus in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete.[8] Concrete was used for construction in many ancient structures.[9]

The Romans used concrete extensively from 300 BC to 476 AD, a span of more than seven hundred years.[10] During the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension.[11]

Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.[12]

Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2 [20 MPa; 2,800 psi]).[13] However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, and its mode of application was also different:[14]

Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.[15]

The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby crystallization of strätlingite and the coalescence of calcium–aluminum-silicate–hydrate cementing binder helped give the concrete a greater degree of fracture resistance even in seismically active environments.[16] Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al-tobermorite crystals over time.[17][18]

Smeaton's Tower

The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon.

After the Roman Empire, the use of burned lime and pozzolana was greatly reduced until the technique was all but forgotten between 500 and the 14th century. From the 14th century to the mid-18th century, the use of cement gradually returned. The Canal du Midi was built using concrete in 1670.[19]

Perhaps the greatest driver behind the modern use of concrete was Smeaton's Tower, the third Eddystone Lighthouse in Devon, England. To create this structure, between 1756 and 1759, British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.[20]

Developed in England in the 19th century, a method for producing Portland cement was patented by Joseph Aspdin in 1824.[21] Aspdin named it due to its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England. His son William Aspdin is regarded as the inventor of "modern" Portland cement due to his developments in the 1840s.[22]

Reinforced concrete was invented in 1849 by Joseph Monier.[23] In 1889 the first concrete reinforced bridge was built, and the first large concrete dams were built in 1936, Hoover Dam and Grand Coulee Dam.[24]

Many types of concrete are available, distinguished by the proportions of the main ingredients below. In this way or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application. Strength, density, as well chemical and thermal resistance are variables.

Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone, or granite, along with finer materials such as sand.

Cement, most commonly Portland cement, is associated with the general term "concrete." A range of other materials can be used as the cement in concrete too. One of the most familiar of these alternative cements is asphalt concrete. Other cementitious materials such as fly ash and slag cement, are sometimes added as mineral admixtures (see below) - either pre-blended with the cement or directly as a concrete component - and become a part of the binder for the aggregate.

To produce concrete from most cements (excluding asphalt), water is mixed with the dry powder and aggregate, which produces a semi-liquid slurry that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, creating a robust stone-like material.

Chemical admixtures are added to achieve varied properties. These ingredients may accelerate or slow down the rate at which the concrete hardens, and impart many other useful properties including increased tensile strength, entrainment of air and water resistance.

Reinforcement is often included in concrete. Concrete can be formulated with high compressive strength, but always has lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension, typically steel rebar.

Mineral admixtures have become more popular over recent decades. The use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation, and the discovery that such materials often have complementary and valuable properties. The most conspicuous of these are fly ash, a by-product of coal-fired power plants, ground granulated blast furnace slag, a byproduct of steelmaking, and silica fume, a byproduct of industrial electric arc furnaces. The use of these materials in concrete reduces the amount of resources required, as the mineral admixtures act as a partial cement replacement. This displaces some cement production, an energetically expensive and environmentally problematic process, while reducing the amount of industrial waste that must be disposed of. Mineral admixtures can be pre-blended with the cement during its production for sale and use as a blended cement, or mixed directly with other components when the concrete is produced.

The mix design depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure.

Main article: Cement A few tons of bagged cement. This amount represents about two minutes of output from a 10,000 ton per day cement kiln.

Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar and many plasters. British masonry worker Joseph Aspdin patented Portland cement in 1824. It was named because of the similarity of its colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of calcium silicates (alite, belite), aluminates and ferrites - compounds which combine calcium, silicon, aluminium and iron in forms which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminium and iron) and grinding this product (called clinker) with a source of sulfate (most commonly gypsum).

In modern cement kilns many advanced features are used to lower the fuel consumption per ton of clinker produced. Cement kilns are extremely large, complex, and inherently dusty industrial installations, and have emissions which must be controlled. Of the various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement. Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels.[25]

Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely.[26]

As stated by Abrams' law, a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump.[27] Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.[28]

Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles and other components of the concrete to form a solid mass.[29]

Reaction:[29]

Cement chemist notation: C3S + H → C-S-H + CH Standard notation: Ca3SiO5 + H2O → (CaO)·(SiO2)·(H2O)(gel) + Ca(OH)2 Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2 (approximately; the exact ratios of the CaO, SiO2 and H2O in C-S-H can vary) Crushed stone aggregate Main article: Construction aggregate

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.

The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as pasting the surfaces of the aggregate together, and is typically the most expensive component. Thus variation in sizes of the aggregate reduces the cost of concrete.[30] The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete.

Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients.[31]

Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers.

In addition to being decorative, exposed aggregate may add robustness to a concrete.[32]

Constructing a rebar cage. This cage will be permanently embedded in poured concrete to create a reinforced concrete structure. Main article: Reinforced concrete

Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete adds either steel reinforcing bars, steel fibers, glass fibers, or plastic fibers to carry tensile loads.

Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement and are added to the concrete at the time of batching/mixing.[33] (See the section on Concrete Production, below.)The common types of admixtures[34] are as follows:

Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures),[33] or as a replacement for Portland cement (blended cements).[39] Products which incorporate limestone, fly ash, blast furnace slag, and other useful materials with pozzolanic properties into the mix, are being tested and used. This development is due to cement production being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions,[40] as well as lowering costs, improving concrete properties, and recycling wastes.

Concrete plant facility showing a Concrete mixer being filled from the ingredient silos.

Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant, or often a batch plant.

In general usage, concrete plants come in two main types, ready mix plants and central mix plants. A ready mix plant mixes all the ingredients except water, while a central mix plant mixes all the ingredients including water. A central mix plant offers more accurate control of the concrete quality through better measurements of the amount of water added, but must be placed closer to the work site where the concrete will be used, since hydration begins at the plant.

A concrete plant consists of large storage hoppers for various reactive ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense the mixed concrete, often to a concrete mixer truck.

Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms, which are containers erected in the field to give the concrete its desired shape. Concrete formwork can be prepared in several ways, such as Slip forming and Steel plate construction. Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture Precast concrete products.

A wide variety of equipment is used for processing concrete, from hand tools to heavy industrial machinery. Whichever equipment builders use, however, the objective is to produce the desired building material; ingredients must be properly mixed, placed, shaped, and retained within time constraints. Any interruption in pouring the concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches.[46] Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect the quality and nature of the product.

When initially mixed, Portland cement and water rapidly form a gel of tangled chains of interlocking crystals, and components of the gel continue to react over time. Initially the gel is fluid, which improves workability and aids in placement of the material, but as the concrete sets, the chains of crystals join into a rigid structure, counteracting the fluidity of the gel and fixing the particles of aggregate in place. During curing, the cement continues to react with the residual water in a process of hydration. In properly formulated concrete, once this curing process has terminated the product has the desired physical and chemical properties. Among the qualities typically desired, are mechanical strength, low moisture permeability, and chemical and volumetric stability.

See also: Volumetric concrete mixer and Concrete mixer

Thorough mixing is essential for the production of uniform, high-quality concrete. For this reason equipment and methods should be capable of effectively mixing concrete materials containing the largest specified aggregate to produce uniform mixtures of the lowest slump practical for the work.

Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete.[47] The paste is generally mixed in a high-speed, shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers, pigments, or silica fume. The premixed paste is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment.[48]

Decorative plate made of Nano concrete with High-Energy Mixing (HEM) Pouring and smoothing out concrete at Palisades Park in Washington DC. Main article: Concrete slump test

Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration) and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate blend with an undesirable gradation[49] can result in a very harsh mix design with a very low slump, which cannot readily be made more workable by addition of reasonable amounts of water. An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in a mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish.[50]

Workability can be measured by the concrete slump test, a simple measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively dry sample slumps very little, having a slump value of one or two inches (25 or 50 mm) out of one foot (305 mm). A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the flow table test.

Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio.[51] Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

After mixing, concrete is a fluid and can be pumped to the location where needed.

A concrete slab ponded while curing.

A common misconception is that concrete dries as it sets, but the opposite is true - damp concrete sets better than dry concrete. In other words, "hydraulic cement" needs water to become strong. Too much water is counterproductive, but too little water is deleterious. Curing allows concrete to achieve optimal strength and hardness.[52] Curing is the hydration process that occurs after the concrete has been placed. In chemical terms, curing allows calcium-silicate hydrate (C-S-H) to form. To gain strength and harden fully, concrete curing requires time. In around 4 weeks, typically over 90% of the final strength is reached, although strengthening may continue for decades.[53] The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO2 over several decades further strengthens the concrete and makes it more resistant to damage. This carbonation reaction, however, lowers the pH of the cement pore solution and can corrode the reinforcement bars.

Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.[54] Addition of short-cut polymer fibers can improve (reduce) shrinkage-induced stresses during curing and increase early and ultimate compression strength.[55]

Properly curing concrete leads to increased strength and lower permeability and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing or overheating due to the exothermic setting of cement. Improper curing can cause scaling, reduced strength, poor abrasion resistance and cracking.

During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds. After the concrete is sufficiently cured, the film is allowed to abrade from the concrete through normal use.[56]

Traditional conditions for curing involve by spraying or ponding the concrete surface with water. The picture to the right shows one of many ways to achieve this, ponding – submerging setting concrete in water and wrapping in plastic to prevent dehydration. Additional common curing methods include wet burlap and plastic sheeting covering the fresh concrete.

For higher-strength applications, accelerated curing techniques may be applied to the concrete. One common technique involves heating the poured concrete with steam, which serves to both keep it damp and raise the temperature, so that the hydration process proceeds more quickly and more thoroughly.

Main article: Pervious concrete

Pervious concrete is a mix of specially graded coarse aggregate, cement, water and little-to-no fine aggregates. This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles. The hardened concrete contains interconnected air voids totalling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath. Air entrainment admixtures are often used in freeze–thaw climates to minimize the possibility of frost damage.

Two-layered pavers, top layer made of pigmented HEM Nanoconcrete.

Nanoconcrete is created by high-energy mixing (HEM) of cement, sand and water. To ensure the mixing is thorough enough to create nano-concrete, the mixer must apply a total mixing power to the mixture of 30 - 600 watts per kilogram of the mix. This mixing must continue long enough to yield a net specific energy expended upon the mix of at least 5000 joules per kilogram of the mix.[57] A plasticizer or a superplasticizer is then added to the activated mixture which can later be mixed with aggregates in a conventional concrete mixer. In the HEM process, the intense mixing of cement and water with sand provides dissipation of energy and increases shear stresses on the surface of cement particles. This intense mixing serves to divide the cement particles into extremely fine nanometer scale sizes, which provides for extremely thorough mixing. This results in the increased volume of water interacting with cement and acceleration of Calcium Silicate Hydrate (C-S-H) colloid creation.

The initial natural process of cement hydration with formation of colloidal globules about 5 nm in diameter[58] spreads into the entire volume of cement – water matrix as the energy expended upon the mix approaches and exceeds 5000 joules per kilogram.

The liquid activated high-energy mixture can be used by itself for casting small architectural details and decorative items, or foamed (expanded) for lightweight concrete. HEM Nanoconcrete hardens in low and subzero temperature conditions and possesses an increased volume of gel, which reduces capillarity in solid and porous materials.

Bacteria such as Bacillus pasteurii, Bacillus pseudofirmus, Bacillus cohnii, Sporosarcina pasteuri, and Arthrobacter crystallopoietes increase the compression strength of concrete through their biomass. Not all bacteria increase the strength of concrete significantly with their biomass.[59]:143 Bacillus sp. CT-5. can reduce corrosion of reinforcement in reinforced concrete by up to four times. Sporosarcina pasteurii reduces water and chloride permeability. B. pasteurii increases resistance to acid.[59]:146 Bacillus pasteurii and B. sphaericuscan induce calcium carbonate precipitation in the surface of cracks, adding compression strength.[59]:147

Main article: Polymer concrete

Polymer concretes are mixtures of aggregate and any of various polymers and may be reinforced. The cement is more costly than lime-based cements, but polymer concretes nevertheless have advantages, they have significant tensile strength even without reinforcement, and they are largely impervious to water. They are frequently used for repair and construction of other applications such as drains.

Concrete, when ground, can result in the creation of hazardous dust. The National Institute for Occupational Safety and Health in the United States recommends attaching local exhaust ventilation shrouds to electric concrete grinders to control the spread of this dust.[60]

Main article: Properties of concrete

Concrete has relatively high compressive strength, but much lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.

Tests can be performed to ensure that the properties of concrete correspond to specifications for the application.

Compression testing of a concrete cylinder

Different mixes of concrete ingredients produce different strengths. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.

Different strengths of concrete are used for different purposes. Very low-strength - 14 MPa (2,000 psi) or less - concrete may be used when the concrete must be lightweight.[61] Lightweight concrete is often achieved by adding air, foams, or lightweight aggregates, with the side effect that the strength is reduced. For most routine uses, 20 MPa (2,900 psi) to 32 MPa (4,600 psi) concrete is often used. 40 MPa (5,800 psi) concrete is readily commercially available as a more durable, although more expensive, option. Higher-strength concrete is often used for larger civil projects.[62] Strengths above 40 MPa (5,800 psi) are often used for specific building elements. For example, the lower floor columns of high-rise concrete buildings may use concrete of 80 MPa (11,600 psi) or more, to keep the size of the columns small. Bridges may use long beams of high-strength concrete to lower the number of spans required.[63][64] Occasionally, other structural needs may require high-strength concrete. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Strengths as high as 130 MPa (18,900 psi) have been used commercially for these reasons.[63]

The Buffalo City Court Building in Buffalo, NY.

Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction and gains strength over time. Structures made of concrete can have a long service life. Concrete is used more than any other human-made material in the world.[65] As of 2006, about 7.5 billion cubic meters of concrete are made each year, more than one cubic meter for every person on Earth.[66]

Main article: Mass concrete Aerial photo of reconstruction at Taum Sauk (Missouri) pumped storage facility in late November, 2009. After the original reservoir failed, the new reservoir was made of roller-compacted concrete.

Due to cement's exothermic chemical reaction while setting up, large concrete structures such as dams, navigation locks, large mat foundations, and large breakwaters generate excessive heat during hydration and associated expansion. To mitigate these effects post-cooling[67] is commonly applied during construction. An early example at Hoover Dam, installed a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating. Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed. Various methods also are used to pre-cool the concrete mix in mass concrete structures.[67]

Another approach to mass concrete structures that minimizes cement's thermal byproduct is the use of roller-compacted concrete, which uses a dry mix which has a much lower cooling requirement than conventional wet placement. It is deposited in thick layers as a semi-dry material then roller compacted into a dense, strong mass.

Main article: Decorative concrete Black basalt polished concrete floor

Raw concrete surfaces tend to be porous, and have a relatively uninteresting appearance. Many different finishes can be applied to improve the appearance and preserve the surface against staining, water penetration, and freezing.

Examples of improved appearance include stamped concrete where the wet concrete has a pattern impressed on the surface, to give a paved, cobbled or brick-like effect, and may be accompanied with coloration. Another popular effect for flooring and table tops is polished concrete where the concrete is polished optically flat with diamond abrasives and sealed with polymers or other sealants.

Other finishes can be achieved with chiselling, or more conventional techniques such as painting or covering it with other materials.

The proper treatment of the surface of concrete, and therefore its characteristics, is an important stage in the construction and renovation of architectural structures.[68]

40-foot cacti decorate a sound/retaining wall in Scottsdale, Arizona Main article: Prestressed concrete

Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those experienced in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. For example, a horizontal beam tends to sag. Prestressed reinforcement along the bottom of the beam counteracts this. In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.

More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days. See Brutalism.

Extreme weather conditions (extreme heat or cold; windy condition, and humidity variations) can significantly alter the quality of concrete. In cold weather concreting, many precautions are observed.[69] Low temperatures significantly slow the chemical reactions involved in hydration of cement, thus affecting the strength development. Preventing freezing is the most important precaution, as formation of ice crystals can cause damage to the crystalline structure of the hydrated cement paste. If the surface of the concrete pour is insulated from the outside temperatures, the heat of hydration will prevent freezing.

The American Concrete Institute (ACI) definition of cold weather concreting, ACI 306,[70] is:

In Canada, where temperatures tend to be much lower during the cold season, the following criteria is used by CSA A23.1:

The minimum strength before exposing concrete to extreme cold is 500 psi (3.5 MPa). CSA A 23.1 specified a compressive strength of 7.0 MPa to be considered safe for exposure to freezing.

Concrete roads are more fuel efficient to drive on,[71] more reflective and last significantly longer than other paving surfaces, yet have a much smaller market share than other paving solutions. Modern-paving methods and design practices have changed the economics of concrete paving, so that a well-designed and placed concrete pavement will be less expensive on initial costs and significantly less expensive over the life cycle. Another major benefit is that pervious concrete can be used, which eliminates the need to place storm drains near the road, and reducing the need for slightly sloped roadway to help rainwater to run off. No longer requiring discarding rainwater through use of drains also means that less electricity is needed (more pumping is otherwise needed in the water-distribution system), and no rainwater gets polluted as it no longer mixes with polluted water. Rather, it is immediately absorbed by the ground.

Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Similarly, relatively little energy is used in producing and combining the raw materials (although large amounts of CO2 are produced by the chemical reactions in cement manufacture).[72] The overall embodied energy of concrete at roughly 1 to 1.5 megajoules per kilogram is therefore lower than for most structural and construction materials.[73]

Once in place, concrete offers great energy efficiency over the lifetime of a building.[74] Concrete walls leak air far less than those made of wood frames.[75] Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs.[76] While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. Insulating concrete forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

A modern building: Boston City Hall (completed 1968) is constructed largely of concrete, both precast and poured in place. Of Brutalist architecture, it was voted "The World's Ugliest Building" in 2008.

Concrete buildings are more resistant to fire than those constructed using steel frames, since concrete has lower heat conductivity than steel and can thus last longer under the same fire conditions. Concrete is sometimes used as a fire protection for steel frames, for the same effect as above. Concrete as a fire shield, for example Fondu fyre, can also be used in extreme environments like a missile launch pad.

Options for non-combustible construction include floors, ceilings and roofs made of cast-in-place and hollow-core precast concrete. For walls, concrete masonry technology and Insulating Concrete Forms (ICFs) are additional options. ICFs are hollow blocks or panels made of fireproof insulating foam that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

Concrete also provides good resistance against externally applied forces such as high winds, hurricanes, and tornadoes owing to its lateral stiffness, which results in minimal horizontal movement. However this stiffness can work against certain types of concrete structures, particularly where a relatively higher flexing structure is required to resist more extreme forces.

As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcement, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally.[77] These risks can be reduced through seismic retrofitting of at-risk buildings, (e.g. school buildings in Istanbul, Turkey[78]).

Concrete spalling caused by the corrosion of rebar Main article: Concrete degradation

Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonatation, chlorides, sulfates and distillate water).[citation needed] The micro fungi Aspergillus Alternaria and Cladosporium were able to grow on samples of concrete used as a radioactive waste barrier in the Chernobyl reactor; leaching aluminium, iron, calcium and silicon.[79]

The Tunkhannock Viaduct began service in 1912 and is still in regular use more than 100 years later.

Concrete can be viewed as a form of artificial sedimentary rock. As a type of mineral, the compounds of which it is composed are extremely stable.[80] Many concrete structures are built with an expected lifetime of approximately 100 years,[81] but researchers have suggested that adding silica fume could extend the useful life of bridges and other concrete uses to as long as 16,000 years.[82] Coatings are also available to protect concrete from damage, and extend the useful life. Epoxy coatings may be applied only to interior surfaces, though, as they would otherwise trap moisture in the concrete.[83]

A self-healing concrete has been developed that can also last longer than conventional concrete.[84] Another option is to use hydrophobic concrete.

Concrete mixing plant in Birmingham, Alabama in 1936

Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, highways, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Concrete is used in large quantities almost everywhere mankind has a need for infrastructure. Concrete is one of the most frequently used building materials in animal houses and for manure and silage storage structures in agriculture.[85]

The amount of concrete used worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Concrete's use in the modern world is exceeded only by that of naturally occurring water.[86]

Concrete is also the basis of a large commercial industry. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $100 billion in revenue by 2015.[87] In the United States alone, concrete production is a $30-billion-per-year industry, considering only the value of the ready-mixed concrete sold each year.[88] Given the size of the concrete industry, and the fundamental way concrete is used to shape the infrastructure of the modern world, it is difficult to overstate the role this material plays today.

Main article: Environmental impact of concrete

The manufacture and use of concrete produce a wide range of environmental and social consequences. Some are harmful, some welcome, and some both, depending on circumstances.

A major component of concrete is cement, which similarly exerts environmental and social effects.[59]:142 The cement industry is one of the three primary producers of carbon dioxide, a major greenhouse gas (the other two being the energy production and transportation industries). As of 2001, the production of Portland cement contributed 7% to global anthropogenic CO2 emissions, largely due to the sintering of limestone and clay at 1,500 °C (2,730 °F).[89]

Concrete is used to create hard surfaces that contribute to surface runoff, which can cause heavy soil erosion, water pollution, and flooding, but conversely can be used to divert, dam, and control flooding.

Concrete is a contributor to the urban heat island effect, though less so than asphalt.[90]

Workers who cut, grind or polish concrete are at risk of inhaling airborne silica, which can lead to silicosis.[91] Concrete dust released by building demolition and natural disasters can be a major source of dangerous air pollution.

The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns due to toxicity and radioactivity. Fresh concrete (before curing is complete) is highly alkaline and must be handled with proper protective equipment.

Recycled crushed concrete, to be reused as granular fill, is loaded into a semi-dump truck. Main article: Concrete recycling

Concrete recycling is an increasingly common method for disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws and economic benefits.

Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks and rocks.

Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On 3 March 1983, a government-funded research team (the VIRL research.codep) estimated that almost 17% of worldwide landfill was by-products of concrete based waste.[citation needed]

The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years. The previous record was 12.3 million cubic meters held by Itaipu hydropower station in Brazil.[92][93][93][94]

The world record for concrete pumping was set on 7 August 2009 during the construction of the Parbati Hydroelectric Project, near the village of Suind, Himachal Pradesh, India, when the concrete mix was pumped through a vertical height of 715 m (2,346 ft).[95][96]

The world record for the largest continuously poured concrete raft was achieved in August 2007 in Abu Dhabi by contracting firm Al Habtoor-CCC Joint Venture and the concrete supplier is Unibeton Ready Mix.[97][98] The pour (a part of the foundation for the Abu Dhabi's Landmark Tower) was 16,000 cubic meters of concrete poured within a two-day period.[99] The previous record, 13,200 cubic meters poured in 54 hours despite a severe tropical storm requiring the site to be covered with tarpaulins to allow work to continue, was achieved in 1992 by joint Japanese and South Korean consortiums Hazama Corporation and the Samsung C&T Corporation for the construction of the Petronas Towers in Kuala Lumpur, Malaysia.[100]

The world record for largest continuously poured concrete floor was completed 8 November 1997, in Louisville, Kentucky by design-build firm EXXCEL Project Management. The monolithic placement consisted of 225,000 square feet (20,900 m2) of concrete placed within a 30-hour period, finished to a flatness tolerance of FF 54.60 and a levelness tolerance of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.[101][102]

The record for the largest continuously placed underwater concrete pour was completed 18 October 2010, in New Orleans, Louisiana by contractor C. J. Mahan Construction Company, LLC of Grove City, Ohio. The placement consisted of 10,251 cubic yards of concrete placed in a 58.5 hour period using two concrete pumps and two dedicated concrete batch plants. Upon curing, this placement allows the 50,180-square-foot (4,662 m2) cofferdam to be dewatered approximately 26 feet (7.9 m) below sea level to allow the construction of the Inner Harbor Navigation Canal Sill & Monolith Project to be completed in the dry.[103]

Sidewalk

Asphalt Surfacing Contractors Price Raised sidewalks beside a 2000-year-old paved road, Pompeii, Italy

A sidewalk (American English) or pavement (British English), also known as a footpath or footway, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade (height) and is normally separated from the vehicular section by a curb. There may also be a median strip or road verge (a strip of vegetation, grass or bushes or trees or a combination of these) either between the sidewalk and the roadway or between the sidewalk and the boundary.

In some places, the same term may also be used for a paved path, trail or footpath that is not next to a road, for example, a path through a park.

The term "sidewalk" is usually preferred in most of North America, along with many other countries worldwide that are not members of the Commonwealth of Nations. The term "pavement" is more common in the United Kingdom,[1] as well as parts of the Mid-Atlantic United States such as Philadelphia and New Jersey.[2][3] Many Commonwealth countries use the term "footpath". The professional, civil engineering and legal term for this in North America is "sidewalk" while in the United Kingdom it is "footway".[4]

In the United States, the term sidewalk is used for the pedestrian path beside a road. "Shared use paths" or "multi-use paths" are available for use by both pedestrians and bicyclists.[5] "Walkway" is a more comprehensive term that includes stairs, ramps, passageways, and related structures that facilitate the use of a path as well as the sidewalk.[6]

In the UK, the term "footpath" is mostly used for paths that do not abut a roadway.[7] The term "shared-use path" is used where cyclists are also able to use the same section of path as pedestrians.[8]

East India House, Leadenhall Street, London, 1766. The sidewalk is separated from the main street by six bollards in front of the building.

There is evidence that sidewalks were built in ancient times. It was claimed that the Greek city of Corinth was paved by the 4th-century, and the Romans were particularly prolific sidewalk builders – they called them semitas.[9]

However, by the Middle Ages, narrow roads had reverted to being simultaneously used by pedestrians and wagons without any formal separation between the two categories. Early attempts at ensuring the adequate maintenance of foot-ways or sidewalks were often made, such as the 1623 Act for Colchester, although they were generally not very effective.[10]

Following the Great Fire of London in 1666, attempts were slowly made to bring some order to the sprawling city. In 1671, 'Certain Orders, Rules and Directions Touching the Paving and Cleansing The Streets, Lanes and Common Passages within the City of London' were formulated, calling for all streets to be adequately paved for pedestrians with cobblestones. Purbeck stone was widely used as a durable paving material. Bollards were also installed to protect pedestrians from the traffic in the middle of the road.

A series of Paving Acts from the House of Commons during the 18th century, especially the 1766 Paving & Lighting Act, authorized the City of London Corporation to create foot-ways throughout all the streets of London, to pave them with Purbeck stone (the thoroughfare in the middle was generally cobblestone) and to raise them above the street level with curbs forming the separation.[11] The Corporation was also made responsible for the regular upkeep of the roads, including their cleaning and repair, for which they charged a tax from 1766.[12] By the late 19th-century large and spacious sidewalks were routinely constructed in European capitals, and were associated with urban sophistication.

In the United States, adjoining property owners must in most situations finance all or part of the cost of sidewalk construction. In a legal case in 1917 involving E. L. Stewart, a former member of the Louisiana House of Representatives and a lawyer in Minden in Webster Parish, the Louisiana Supreme Court ruled that owners must pay whether they wish for the sidewalk to be constructed or not.[13]

Pedestrians walking on the pavement (sidewalk) in London.

Sidewalks play an important role in transportation, as they provide a safe path for people to walk along that is separated from the motorized traffic. They aid road safety by minimizing interaction between pedestrians and motorized traffic. Sidewalks are normally in pairs, one on each side of the road, with the center section of the road for motorized vehicles.

In rural roads, sidewalks may not be present as the amount of traffic (pedestrian or motorized) may not be enough to justify separating the two. In suburban and urban areas, sidewalks are more common. In town and city centers (known as downtown in North America) the amount of pedestrian traffic can exceed motorized traffic, and in this case the sidewalks can occupy more than half of the width of the road, or the whole road can be reserved for pedestrians, see Pedestrian zone.

Sidewalks may have a small effect on reducing vehicle miles traveled and carbon dioxide emissions. A study of sidewalk and transit investments in Seattle neighborhoods found vehicle travel reductions of 6 to 8% and CO2 emission reductions of 1.3 to 2.2% [14]

Sidewalk with bike path See also: Road traffic safety

Research commissioned for the Florida Department of Transportation, published in 2005, found that, in Florida, the Crash Reduction Factor (used to estimate the expected reduction of crashes during a given period) resulting from the installation of sidewalks averaged 74%.[15] Research at the University of North Carolina for the U.S. Department of Transportation found that the presence or absence of a sidewalk and the speed limit are significant factors in the likelihood of a vehicle/pedestrian crash. Sidewalk presence had a risk ratio of 0.118, which means that the likelihood of a crash on a road with a paved sidewalk was 88.2 percent lower than one without a sidewalk. “This should not be interpreted to mean that installing sidewalks would necessarily reduce the likelihood of pedestrian/motor vehicle crashes by 88.2 percent in all situations. However, the presence of a sidewalk clearly has a strong beneficial effect of reducing the risk of a ‘walking along roadway’ pedestrian/motor vehicle crash.” The study does not count crashes that happen when walking across a roadway. The speed limit risk ratio was 1.116, which means that a 16.1-km/h (10-mi/h) increase in the limit yields a factor of (1.116)10 or 3.[16]

The presence or absence of sidewalks was one of three factors that were found to encourage drivers to choose lower, safer speeds.[17]

On the other hand, the implementation of schemes which involve the removal of sidewalks, such as shared space schemes, are reported to deliver a dramatic drop in crashes and congestion too, which indicates that a number of other factors, such as the local speed environment, also play an important role in whether sidewalks are necessarily the best local solution for pedestrian safety.[18]

In cold weather, black ice is a common problem with unsalted sidewalks. The ice forms a thin transparent surface film which is almost impossible to see, and so results in many slips by pedestrians.

Riding bicycles on sidewalks is discouraged since some research shows it to be more dangerous than riding in the street.[19] Some jurisdictions prohibit sidewalk riding except for children. In addition to the risk of cyclist/pedestrian collisions, cyclists face increase risks from collisions with motor vehicles at street crossings and driveways. Riding in the direction opposite to traffic in the adjacent lane is especially risky.[20]

Since residents of neighborhoods with sidewalks are more likely to walk, they tend to have lower rates of cardiovascular disease, obesity, and other health issues related to sedentary lifestyles.[21] Also, children who walk to school have been shown to have better concentration.[22]

Native Americans busking at Orchard Road, Singapore

Some sidewalks may be used as social spaces with sidewalk cafes, markets, or busking musicians, as well as for parking for a variety of vehicles including cars, motorbikes and bicycles.

Contemporary sidewalks are most often made of concrete in the United States and Canada, while tarmac, asphalt, brick, stone, slab and (increasingly) rubber are more common in Europe.[23] Different materials are more or less friendly environmentally: pumice-based trass, for example, when used as an extender is less energy-intensive than Portland cement concrete or petroleum-based materials such as asphalt or tar-penetration macadam). Multi-use paths alongside roads are sometimes made of materials that are softer than concrete, such as asphalt.

In the 19th century and early 20th century, sidewalks of wood were common in some North American locations. They may still be found at historic beach locations and in conservation areas to protect the land beneath and around, called boardwalks.

Brick sidewalks are found in some urban areas, usually for aesthetic purposes. Brick sidewalk construction usually involves the usage of a mechanical vibrator to lock the bricks in place after they have been laid (and/or to prepare the soil before laying). Although this might also be done by other tools (as regular hammers and heavy rolls), a vibrator is often used to speed up the process.

Stone slabs called flagstones or flags are sometimes used where an attractive appearance is required, as in historic town centers. In other places, pre-cast concrete slabs (called paving slabs or, less correctly, paving stones) are used. These may be colored or textured to resemble stone.

Freshly laid concrete sidewalk, with horizontal strain-relief grooves faintly visible

In the United States and Canada, the most common type of sidewalk consists of a poured concrete ribbon, examples of which from as early as the 1860s can be found in good repair in San Francisco, and stamped with the name of the contractor and date of installation.[citation needed] When quantities of Portland cement were first imported to the United States in the 1880s, its principal use was in the construction of sidewalks.[24]

Today, most sidewalk ribbons are constructed with cross-lying strain-relief grooves placed or sawn at regular intervals typically 5 feet (1.5 m) apart. This partitioning, an improvement over the continuous slab, was patented in 1924 by Arthur Wesley Hall and William Alexander McVay, who wished to minimize damage to the concrete from the effects of tectonic and temperature fluctuations, both of which can crack longer segments.[25] The technique is not perfect, as freeze-thaw cycles (in cold-weather regions) and tree root growth can eventually result in damage which requires repair.

In highly variable climates which undergo multiple freeze-thaw cycles, the concrete blocks will be separated by expansion joints to allow for thermal expansion without breakage. The use of expansion joints in sidewalks may not be necessary, as the concrete will shrink while setting.[26]

In the United Kingdom, Australia and France suburban sidewalks are most commonly constructed of tarmac. In urban or inner-city areas sidewalks are most commonly constructed of slabs, stone, or brick depending upon the surrounding street architecture and furniture.

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https://www.helpwikileaks.co.za/boksburg/

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Asphalt Driveway Repair Companies Centurion

For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Asphalt Driveway Repair Companies in Centurion except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

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Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪtʃəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)uːmən, baɪˈt(j)uːmən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

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The primary use (70%) of asphalt Paver Driveway Installation is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as “tar”, as in the name of the La Brea Tar Pits.

Toll road

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Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Asphalt Driveway Repair Companies Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.

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The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”.  Asphalt Emulsion Companies the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.

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The expression “bitumen” originated in the Sanskrit words jatu, meaning “pitch”, and jatu-krit, meaning “pitch creating” or “pitch producing” (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.

In British English, “bitumen” is used instead of “asphalt”. The word “asphalt” is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called “tarmac” in common parlance). Bitumen mixed with clay was usually called “asphaltum”,[13] but the term is less commonly used today.[citation needed]

Lane

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In Australian English, “bitumen” is often used as the generic term for road surfaces.

In American English, “asphalt” is equivalent to the British “bitumen”. However, “asphalt” is also commonly used as a shortened form of “asphalt concrete” (therefore equivalent to the British “asphalt” or “tarmac”).

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In Canadian English, the word “bitumen” is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while “asphalt” is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as “dilbit” in the Canadian petroleum industry, while bitumen “upgraded” to synthetic crude oil is known as “syncrude”, and syncrude blended with bitumen is called “synbit”.[15]

“Bitumen” is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. “Bituminous rock” is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

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Neither of the terms “asphalt” or “bitumen” should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.

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The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] “It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large”.

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word “tarmac”, which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. “Pitch” is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

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Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

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Bitumen also occurs in unconsolidated sandstones known as “oil sands” in Alberta, Canada, and the similar “tar sands” in Utah, US. The Canadian province of Alberta has most of the world’s reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.

Diverging diamond interchange

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The world’s largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.

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Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.

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Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.

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The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.

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The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians’ primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

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Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.

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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.

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In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.

Sidewalk

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An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by “a certain Monsieur d’Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel”, and that he proposed to use it in a variety of ways – “principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth”, which at that time made the water unusable. “He expatiates also on the excellence of this material for forming level and durable terraces” in palaces, “the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation”.

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But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used “for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes”. Its rise in Europe was “a sudden phenomenon”, after natural deposits were found “in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)”, although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon’s Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.

Asphalt Driveway Near Me

The first British patent for the use of asphalt was “Cassell’s patent asphalte or bitumen” in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also “instrumental in introducing the asphalte pavement (in 1836)”.[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.

Toll road

Asphalt Installation Cost Estimate

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge. Claridge’s Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain “Asphalte in its natural state from the mine at Pyrimont Seysell in France”,—”laid one of the first asphalt pavements in Whitehall”.  Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,”and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park”. “The formation in 1838 of Claridge’s Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry”.[45] “By the end of 1838, at least two other companies, Robinson’s and the Bastenne company, were in production”,[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge’s Whitehall paving “continue(d) in good order”.

Asphalt Driveway Repair Companies in Centurion ?

Pave My Driveway Costs Moderate to severe Fatigue cracking.

Crocodile cracking, also called alligator cracking and perhaps misleadingly fatigue cracking, is a common type of distress in asphalt pavement. The following is more closely related to fatigue cracking which is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile.[1] Cell sizes can vary in size up to 11.80 inches (300 mm) across, but are typically less than 5.90 inches (150 mm) across. Fatigue cracking is generally a loading failure,[1] but numerous factors can contribute to it. It is often a sign of sub-base failure, poor drainage, or repeated over-loadings. It is important to prevent fatigue cracking, and repair as soon as possible, as advanced cases can be very costly to repair and can lead to formation of potholes or premature pavement failure.

It is usually studied under the transportation section of civil engineering.

Fatigue cracking is an asphalt pavement distress most often instigated by failure of the surface due to traffic loading. However, fatigue cracking can be greatly influenced by environmental and other effects while traffic loading remains the direct cause. Frequently, overloading happens because the base or subbase inadequately support the surface layer and subsequently cannot handle loads that it would normally endure.[2] There are many ways that the subbase or base can be weakened.

Poor drainage in the road bed is a frequent cause of this degradation of the base or subgrade.[1] A heavy spring thaw, similarly to poor drainage, can weaken the base course, leading to fatigue cracking.[1]

Stripping or raveling is another possible cause of fatigue cracking. Stripping occurs when poor adhesion between asphalt and aggregate allows the aggregate at the surface to dislodge. If left uncorrected, this reduces the thickness of the pavement, reducing the affected portion's ability to carry its designed loading.[1] This can cause fatigue cracking to develop rapidly, as overloading will happen with loads of less magnitude or frequency.

Edge cracking is the formation of crescent-shaped cracks near the edge of a road.[3] It is caused by lack of support of the road edge, sometimes due to poorly drained or weak shoulders. If left untreated, additional cracks will form until it resembles fatigue cracking.[3] Like wheel-path fatigue cracking, poor drainage is a main cause of edge cracking, as it weakens the base, which hastens the deterioration of the pavement.[4] Water ponding (a buildup of water which can also be called puddling) happens more frequently near the edge than in the center of the road path, as roads are usually sloped to prevent in-lane ponding. This leads to excess moisture in the shoulders and subbase at the road edge. Edge cracking differs from fatigue cracking in that the cracks form from the top down, where fatigue cracks usually start at the bottom and propagate to the surface.

Fatigue cracking manifests itself initially as longitudinal cracking (cracks along the direction of the flow of traffic) in the top layer of the asphalt.[5] These cracks are initially thin and sparsely distributed. If further deterioration is allowed, these longitudinal cracks are connected by transverse cracks to form sharp sided, prismatic pieces. This interlaced cracking pattern resembles the scales on the back of a crocodile or alligator, hence the nickname, crocodile cracking.

More severe cases involve pumping of fines, spalling, and loose pieces of pavement. The most severe cases of fatigue cracking often occur with other pavement distresses, but are exemplified by: potholes,[1] large cracks(3/8" or larger), and severely spalled edges.[4]

There are many different ways to measure fatigue cracking, but in general a pavement distress manual or index will be used. For example, the Pavement Condition Index is widely used to quantify the overall level of distress and condition of a section of road. Measurement of fatigue cracking specifically (and pavement distress in general) is necessary to determine the overall condition of a road, and for determination of a time-line for rehabilitation and/or repair. There are many other rating systems, and many rating systems currently in use are based on the AASHO Road Test.

There are two important criteria to take into account when measuring fatigue cracking. The first is the extent of the cracking. This is the amount of road surface area which is affected by this pavement distress. The second criterion is the severity of the cracking.[6] Severity, which has been discussed above, refers to how far the cracking has progressed, and is often directly a function of crack width.[6] Severity may be rated numerically, or given a rating from "low" to "severe". The rating may be entered into a pavement management system, which will suggest a priority and method for the repair.

Systems have been developed that detect fatigue cracking and other types of pavement distress automatically.[7] They measure the severity and frequency of alligator cracking on the road-path. One such machine is the road surface profilometer, which is mounted on a vehicle and measures the profile of the road surface while it is moving down the roadway.

Preventing fatigue cracking can be as simple as preventing the common causes. For example, reducing overloading on an asphalt pavement or improving drainage[2] can prevent fatigue cracking in many cases. Prevention primarily depends on designing and constructing the pavement and subbase to support the expected traffic loads, and providing good drainage to keep water out of the subbase.

A good strategy to prevent overloading, which is a main cause of fatigue cracking, is to increase the depth of the asphalt layer. According to certain researchers, pavements that exceed a certain minimum strength or thickness can hypothetically handle infinitely many loads without showing structural defects, including fatigue cracking.[1] These pavements are called perpetual pavements or long-term performance pavements (LTPP).

When repairing pavement affected by fatigue cracking, the main cause of the distress should be determined. However, often the specific cause is fairly difficult to determine, and prevention is therefore correspondingly difficult. Any investigation should involve digging a pit or coring the pavement and subbase to determine the pavement's structural makeup as well as determining whether or not subsurface moisture is a contributing factor.[1] The repair needed also differs based on the severity and extent of the cracking.

In the early stages, sealing cracks with crack sealant limits further deterioration of the subgrade due to moisture penetration. Small areas may be repaired by removal of the affected area, and replacement with new base and asphalt surface.[2] Once the damage has progressed or the affected area is large and extensive, a structural asphalt overlay or complete reconstruction is necessary to ensure structural integrity. Proper repair may include first sealing cracks with crack sealant, installing paving fabric over a tack coat, or milling the damaged asphalt. An overlay of hot mix asphalt is then placed over the completed repair. [2]

Lane

Paving Companies Near Me For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt

Asphalt (/ˈæsˌfɔːlt, -ˌfɑːlt/), also known as bitumen (UK English: /ˈbɪəmən, ˈbɪtjʊmən/,[1] US English: /bɪˈt(j)mən, bˈt(j)mən/)[2] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.[3] The word is derived from the Ancient Greek ἄσφαλτος ásphaltos.[4]

The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.[5]

The terms "asphalt" and "bitumen" are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, "asphalt" (or "asphalt cement") is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called "bitumen", and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt as "tar", as in the name of the La Brea Tar Pits.

Naturally occurring asphalt is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of cold molasses[6][7] while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as "refined bitumen". The Canadian province of Alberta has most of the world's reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.[8]

The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch",[9] which perhaps derives from ἀ-, "without" and σφάλλω (sfallō), "make fall".[10] The first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.[11] From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads.

The expression "bitumen" originated in the Sanskrit words jatu, meaning "pitch", and jatu-krit, meaning "pitch creating" or "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally gwitu-men (pertaining to pitch), and by others, pixtumens (exuding or bubbling pitch), which was subsequently shortened to bitumen, thence passing via French into English. From the same root is derived the Anglo-Saxon word cwidu (mastix), the German word Kitt (cement or mastic) and the old Norse word kvada.[12]

In British English, "bitumen" is used instead of "asphalt". The word "asphalt" is instead used to refer to asphalt concrete, a mixture of construction aggregate and asphalt itself (also called "tarmac" in common parlance). Bitumen mixed with clay was usually called "asphaltum",[13] but the term is less commonly used today.[citation needed]

In Australian English, "bitumen" is often used as the generic term for road surfaces.

In American English, "asphalt" is equivalent to the British "bitumen". However, "asphalt" is also commonly used as a shortened form of "asphalt concrete" (therefore equivalent to the British "asphalt" or "tarmac").

In Canadian English, the word "bitumen" is used to refer to the vast Canadian deposits of extremely heavy crude oil,[14] while "asphalt" is used for the oil refinery product. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as "dilbit" in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as "syncrude", and syncrude blended with bitumen is called "synbit".[15]

"Bitumen" is still the preferred geological term for naturally occurring deposits of the solid or semi-solid form of petroleum. "Bituminous rock" is a form of sandstone impregnated with bitumen. The tar sands of Alberta, Canada are a similar material.

Neither of the terms "asphalt" or "bitumen" should be confused with tar or coal tars.[further explanation needed]

See also: Asphaltene

The components of asphalt include four main classes of compounds:

The naphthene aromatics and polar aromatics are typically the majority components. Most natural bitumens also contain organosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel and vanadium are found at <10 parts per million, as is typical of some petroleum.[5]

The substance is soluble in carbon disulfide. It is commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase.[16] "It is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".[17]

Asphalt may be confused with coal tar, which is a visually similar black, thermoplastic material produced by the destructive distillation of coal. During the early and mid-20th century, when town gas was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to macadam roads led to the word "tarmac", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt has completely overtaken the use of coal tar in these applications. Other examples of this confusion include the La Brea Tar Pits and the Canadian oil sands, both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in Pitch Lake.

Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France

The majority of asphalt used commercially is obtained from petroleum.[18] Nonetheless, large amounts of asphalt occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These remains were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.

Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and in the Dead Sea.

Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US. The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering 142,000 square kilometres (55,000 sq mi), an area larger than England or New York state. These bituminous sands contain 166 billion barrels (26.4×10^9 m3) of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.[8]

The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil.[19] Isotopic studies show the oil deposits to be about 110 million years old.[20] Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.[21]

Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.[19]

Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.[22]

Bitumen is similar to the organic matter in carbonaceous meteorites.[23] However, detailed studies have shown these materials to be distinct.[24] The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of 50 to 150 °C (120 to 300 °F). Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands.[21]

The use of natural bitumen for waterproofing, and as an adhesive dates at least to the fifth millennium BC, with a crop storage basket discovered in Mehrgarh, of the Indus Valley Civilization, lined with it.[25] By the 3rd millennia BC refined rock asphalt was in use, in the region, and was used to waterproof the Great Bath, Mohenjo-daro.

In the ancient Middle East, the Sumerians used natural bitumen deposits for mortar between bricks and stones, to cement parts of carvings, such as eyes, into place, for ship caulking, and for waterproofing.[3] The Greek historian Herodotus said hot bitumen was used as mortar in the walls of Babylon.[26]

The 1 kilometre (0.62 mi) long Euphrates Tunnel beneath the river Euphrates at Babylon in the time of Queen Semiramis (ca. 800 BC) was reportedly constructed of burnt bricks covered with bitumen as a waterproofing agent.[27]

Bitumen was used by ancient Egyptians to embalm mummies.[3][28] The Persian word for asphalt is moom, which is related to the English word mummy. The Egyptians' primary source of bitumen was the Dead Sea, which the Romans knew as Palus Asphaltites (Asphalt Lake).

Approximately 40 AD, Dioscorides described the Dead Sea material as Judaicum bitumen, and noted other places in the region where it could be found.[29] The Sidon bitumen is thought to refer to material found at Hasbeya.[30] Pliny refers also to bitumen being found in Epirus. It was a valuable strategic resource, the object of the first known battle for a hydrocarbon deposit—between the Seleucids and the Nabateans in 312 BC.[31]

In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher fractions, leaving a thermoplastic material of higher molecular weight that when layered on objects became quite hard upon cooling. This was used to cover objects that needed waterproofing,[3] such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.

In North America, archaeological recovery has indicated bitumen was sometimes used to adhere stone projectile points to wooden shafts.[32] In Canada, aboriginal people used bitumen seeping out of the banks of the Athabasca and other rivers to waterproof birch bark canoes, and also heated it in smudge pots to ward off mosquitoes in the summer.[21]

In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.[33]

An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".[34]

But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially.[35] One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.[36]

Among the earlier uses of bitumen in the United Kingdom was for etching. William Salmon's Polygraphice (1673) provides a recipe for varnish used in etching, consisting of three ounces of virgin wax, two ounces of mastic, and one ounce of asphaltum.[37] By the fifth edition in 1685, he had included more asphaltum recipes from other sources.[38]

The first British patent for the use of asphalt was "Cassell's patent asphalte or bitumen" in 1834.[35] Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement,[39][40] having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain.[41][42] Dr T. Lamb Phipson writes that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)".[43] Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.[36]

Claridge obtained a patent in Scotland on 27 March 1838, and obtained a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837 patent and for both 1838 patents were sought by the trustees of a company previously formed by Claridge.[35][44][45][46] Claridge's Patent Asphalte Company—formed in 1838 for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France",[47]—"laid one of the first asphalt pavements in Whitehall".[48] Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks,[47][49] "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park".[49] "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry".[45] "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production",[50] with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".[51]

In 1838, there was a flurry of entrepreneurial activity involving asphalt, which had uses beyond paving. For example, asphalt could also be used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, both of which were also proliferating in the 19th century.[3][35][52] On the London stockmarket, there were various claims as to the exclusivity of asphalt quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s".[50]

In 1914, Claridge's Company entered into a joint venture to produce tar-bound macadam,[53] with materials manufactured through a subsidiary company called Clarmac Roads Ltd.[54] Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridge's Patent Asphalte Co., although Clarmac was more widely used.[55][note 1] However, the First World War ruined the Clarmac Company, which entered into liquidation in 1915.[57][58] The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up,[59] ceasing operations in 1917,[60][61] having invested a substantial amount of funds into the new venture, both at the outset[59] and in a subsequent attempt to save the Clarmac Company.[57]

The first use of bitumen in the New World was by indigenous peoples. On the west coast, as early as the 13th century, the Tongva, Luiseño and Chumash peoples collected the naturally occurring bitumen that seeped to the surface above underlying petroleum deposits. All three groups used the substance as an adhesive. It is found on many different artifacts of tools and ceremonial items. For example, it was used on rattles to adhere gourds or turtle shells to rattle handles. It was also used in decorations. Small round shell beads were often set in asphaltum to provide decorations. It was used as a sealant on baskets to make them watertight for carrying water, possibly poisoning those who drank the water.[62] Asphalt was used also to seal the planks on ocean-going canoes.

Asphalt was first used to pave streets in the 1870s. At first naturally occurring "bituminous rock" was used, such as at Ritchie Mines in Macfarlan in Ritchie County, West Virginia from 1852 to 1873. In 1876, asphalt-based paving was used to pave Pennsylvania Avenue in Washington DC, in time for the celebration of the national centennial.[63] In the horse-drawn era, streets were unpaved and covered with dirt or gravel. However, that produced uneven wear, opened new hazards for pedestrians and made for dangerous potholes for bicycles and for motor vehicles. Manhattan alone had 130,000 horses in 1900, pulling streetcars, wagons, and carriages, and leaving their waste behind. They were not fast, and pedestrians could dodge and scramble their way across the crowded streets. Small towns continued to rely on dirt and gravel, but larger cities wanted much better streets. They looked to wood or granite blocks by the 1850s.[64] In 1890, a third of Chicago's 2000 miles of streets were paved, chiefly with wooden blocks, which gave better traction than mud. Brick surfacing was a good compromise, but even better was asphalt paving, which was easy to install and to cut through to get at sewers. With London and Paris serving as models, Washington laid 400,000 square yards of asphalt paving by 1882; it became the model for Buffalo, Philadelphia and elsewhere. By the end of the century, American cities boasted 30 million square yards of asphalt paving, well ahead of brick.[65] The streets became faster and more dangerous so electric traffic lights were installed. Electric trolleys (at 12 miles per hour) became the main transportation service for middle class shoppers and office workers until they bought automobiles after 1945 and commuted from more distant suburbs in privacy and comfort on asphalt highways.[66]

See also: Bitumount and History of the petroleum industry in Canada (oil sands and heavy oil)

Canada has the world's largest deposit of natural bitumen in the Athabasca oil sands, and Canadian First Nations along the Athabasca River had long used it to waterproof their canoes. In 1719, a Cree named Wa-Pa-Su brought a sample for trade to Henry Kelsey of the Hudson’s Bay Company, who was the first recorded European to see it. However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."[21]

The value of the deposit was obvious from the start, but the means of extracting the bitumen was not. The nearest town, Fort McMurray, Alberta, was a small fur trading post, other markets were far away, and transportation costs were too high to ship the raw bituminous sand for paving. In 1915, Sidney Ells of the Federal Mines Branch experimented with separation techniques and used the product to pave 600 feet of road in Edmonton, Alberta. Other roads in Alberta were paved with material extracted from oil sands, but it was generally not economic. During the 1920s Dr. Karl A. Clark of the Alberta Research Council patented a hot water oil separation process and entrepreneur Robert C. Fitzsimmons[67] built the Bitumount oil separation plant, which between 1925 and 1958 produced up to 300 barrels (50 m3) per day of bitumen using Dr. Clark's method. Most of the bitumen was used for waterproofing roofs, but other uses included fuels, lubrication oils, printers ink, medicines, rust- and acid-proof paints, fireproof roofing, street paving, patent leather, and fence post preservatives.[21] Eventually Fitzsimmons ran out of money and the plant was taken over by the Alberta government. Today the Bitumount plant is a Provincial Historic Site.[68]

Bitumen was used in early photographic technology. In 1826 or 1827, it was used by French scientist Joseph Nicéphore Niépce to make the oldest surviving photograph from nature. The bitumen was thinly coated onto a pewter plate which was then exposed in a camera. Exposure to light hardened the bitumen and made it insoluble, so that when it was subsequently rinsed with a solvent only the sufficiently light-struck areas remained. Many hours of exposure in the camera were required, making bitumen impractical for ordinary photography, but from the 1850s to the 1920s it was in common use as a photoresist in the production of printing plates for various photomechanical printing processes.[69][70]

Bitumen was the nemesis of many artists during the 19th century. Although widely used for a time, it ultimately proved unstable for use in oil painting, especially when mixed with the most common diluents, such as linseed oil, varnish and turpentine. Unless thoroughly diluted, bitumen never fully solidifies and will in time corrupt the other pigments with which it comes into contact. The use of bitumen as a glaze to set in shadow or mixed with other colors to render a darker tone resulted in the eventual deterioration of many paintings, for instance those of Delacroix. Perhaps the most famous example of the destructiveness of bitumen is Théodore Géricault's Raft of the Medusa (1818–1819), where his use of bitumen caused the brilliant colors to degenerate into dark greens and blacks and the paint and canvas to buckle.[71]

The vast majority of refined asphalt is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use, asphalt is produced to specification. This is achieved either by refining or blending. It is estimated that the current world use of asphalt is approximately 102 million tonnes per year. Approximately 85% of all the asphalt produced is used as the binder in asphalt concrete for roads. It is also used in other paved areas such as airport runways, car parks and footways. Typically, the production of asphalt concrete involves mixing fine and coarse aggregates such as sand, gravel and crushed rock with asphalt, which acts as the binding agent. Other materials, such as recycled polymers (e.g., rubber tyres), may be added to the asphalt to modify its properties according to the application for which the asphalt is ultimately intended.

A further 10% of global asphalt production is used in roofing applications, where its waterproofing qualities are invaluable. The remaining 5% of asphalt is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet tile backing and paint. Asphalt is applied in the construction and maintenance of many structures, systems, and components, such as the following:

Main article: Asphalt concrete

The largest use of asphalt is for making asphalt concrete for road surfaces; this accounts for approximately 85% of the asphalt consumed in the United States. Asphalt concrete pavement mixes are typically composed of 5% asphalt cement and 95% aggregates (stone, sand, and gravel). Due to its highly viscous nature, asphalt cement must be heated so it can be mixed with the aggregates at the asphalt mixing facility. The temperature required varies depending upon characteristics of the asphalt and the aggregates, but warm-mix asphalt technologies allow producers to reduce the temperature required. There are about 4,000 asphalt concrete mixing plants in the US, and a similar number in Europe.[72]

When maintenance is performed on asphalt pavements, such as milling to remove a worn or damaged surface, the removed material can be returned to a facility for processing into new pavement mixtures. The asphalt in the removed material can be reactivated and put back to use in new pavement mixes.[73] With some 95% of paved roads being constructed of or surfaced with asphalt,[74] a substantial amount of asphalt pavement material is reclaimed each year. According to industry surveys conducted annually by the Federal Highway Administration and the National Asphalt Pavement Association, more than 99% of the asphalt removed each year from road surfaces during widening and resurfacing projects is reused as part of new pavements, roadbeds, shoulders and embankments.[75]

Asphalt concrete paving is widely used in airports around the world. Due to the sturdiness and ability to be repaired quickly, it is widely used for runways.

Further information: Fibre mastic asphalt

Mastic asphalt is a type of asphalt that differs from dense graded asphalt (asphalt concrete) in that it has a higher asphalt (binder) content, usually around 7–10% of the whole aggregate mix, as opposed to rolled asphalt concrete, which has only around 5% asphalt. This thermoplastic substance is widely used in the building industry for waterproofing flat roofs and tanking underground. Mastic asphalt is heated to a temperature of 210 °C (410 °F) and is spread in layers to form an impervious barrier about 20 millimeters (0.8 inches) thick.

A number of technologies allow asphalt to be mixed at much lower temperatures. These involve mixing with petroleum solvents to form "cutbacks" with reduced melting point or mixing with water to turn the asphalt into an emulsion. Asphalt emulsions contain up to 70% asphalt and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock, gravel or crushed slag. Slurry seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on the surface of a road. Cold-mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth, and asphalt emulsions are also blended into recycled hot-mix asphalt to create low-cost pavements.

Main article: Synthetic crude oil See also: Petroleum production in Canada

Synthetic crude oil, also known as syncrude, is the output from a bitumen upgrader facility used in connection with oil sand production in Canada. Bituminous sands are mined using enormous (100 ton capacity) power shovels and loaded into even larger (400 ton capacity) dump trucks for movement to an upgrading facility. The process used to extract the bitumen from the sand is a hot water process originally developed by Dr. Karl Clark of the University of Alberta during the 1920s. After extraction from the sand, the bitumen is fed into a bitumen upgrader which converts it into a light crude oil equivalent. This synthetic substance is fluid enough to be transferred through conventional oil pipelines and can be fed into conventional oil refineries without any further treatment. By 2015 Canadian bitumen upgraders were producing over 1 million barrels (160×10^3 m3) per day of synthetic crude oil, of which 75% was exported to oil refineries in the United States.[76]

In Alberta, five bitumen upgraders produce synthetic crude oil and a variety of other products: The Suncor Energy upgrader near Fort McMurray, Alberta produces synthetic crude oil plus diesel fuel; the Syncrude Canada, Canadian Natural Resources, and Nexen upgraders near Fort McMurray produce synthetic crude oil; and the Shell Scotford Upgrader near Edmonton produces synthetic crude oil plus an intermediate feedstock for the nearby Shell Oil Refinery.[77] A sixth upgrader, under construction in 2015 near Redwater, Alberta, will upgrade half of its crude bitumen directly to diesel fuel, with the remainder of the output being sold as feedstock to nearby oil refineries and petrochemical plants.[78]

See also: Western Canadian Select

Canadian bitumen does not differ substantially from oils such as Venezuelan extra-heavy and Mexican heavy oil in chemical composition, and the real difficulty is moving the extremely viscous bitumen through oil pipelines to the refinery. Many modern oil refineries are extremely sophisticated and can process non-upgraded bitumen directly into products such as gasoline, diesel fuel, and refined asphalt without any preprocessing. This is particularly common in areas such as the US Gulf coast, where refineries were designed to process Venezuelan and Mexican oil, and in areas such as the US Midwest where refineries were rebuilt to process heavy oil as domestic light oil production declined. Given the choice, such heavy oil refineries usually prefer to buy bitumen rather than synthetic oil because the cost is lower, and in some cases because they prefer to produce more diesel fuel and less gasoline.[77] By 2015 Canadian production and exports of non-upgraded bitumen exceeded that of synthetic crude oil at over 1.3 million barrels (210×10^3 m3) per day, of which about 65% was exported to the United States.[76]

Because of the difficulty of moving crude bitumen through pipelines, non-upgraded bitumen is usually diluted with natural-gas condensate in a form called dilbit or with synthetic crude oil, called synbit. However, to meet international competition, much non-upgraded bitumen is now sold as a blend of multiple grades of bitumen, conventional crude oil, synthetic crude oil, and condensate in a standardized benchmark product such as Western Canadian Select. This sour, heavy crude oil blend is designed to have uniform refining characteristics to compete with internationally marketed heavy oils such as Mexican Mayan or Arabian Dubai Crude.[77]

Asphalt was used starting in the 1960s as an hydrophobic matrix aiming to encapsulate radioactive waste such as medium-activity salts (mainly soluble sodium nitrate and sodium sulfate) produced by the reprocessing of spent nuclear fuels or radioactive sludges from sedimentation ponds.[79][80] Bituminised radioactive waste containing highly radiotoxic alpha-emitting transuranic elements from nuclear reprocessing plants have been produced at industrial scale in France, Belgium and Japan, but this type of waste conditioning has been abandoned because operational safety issues (risks of fire, as occurred in a bituminisation plant at Tokai Works in Japan)[81][82] and long-term stability problems related to their geological disposal in deep rock formations. One of the main problem is the swelling of asphalt exposed to radiation and to water. Asphalt swelling is first induced by radiation because of the presence of hydrogen gas bubbles generated by alpha and gamma radiolysis.[83][84] A second mechanism is the matrix swelling when the encapsulated hygroscopic salts exposed to water or moisture start to rehydrate and to dissolve. The high concentration of salt in the pore solution inside the bituminised matrix is then responsible for osmotic effects inside the bituminised matrix. The water moves in the direction of the concentrated salts, the asphalt acting as a semi-permeable membrane. This also causes the matrix to swell. The swelling pressure due to osmotic effect under constant volume can be as high as 200 bar. If not properly managed, this high pressure can cause fractures in the near field of a disposal gallery of bituminised medium-level waste. When the bituminised matrix has been altered by swelling, encapsulated radionuclides are easily leached by the contact of ground water and released in the geosphere. The high ionic strength of the concentrated saline solution also favours the migration of radionuclides in clay host rocks. The presence of chemically reactive nitrate can also affect the redox conditions prevailing in the host rock by establishing oxidizing conditions, preventing the reduction of redox-sensitive radionuclides. Under their higher valences, radionuclides of elements such as selenium, technetium, uranium, neptunium and plutonium have a higher solubility and are also often present in water as non-retarded anions. This makes the disposal of medium-level bituminised waste very challenging.

Different type of asphalt have been used: blown bitumen (partly oxidized with air oxygen at high temperature after distillation, and harder) and direct distillation bitumen (softer). Blown bitumens like Mexphalte, with a high content of saturated hydrocarbons, are more easily biodegraded by microorganisms than direct distillation bitumen, with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons.[85]

Concrete encapsulation of radwaste is presently considered a safer alternative by the nuclear industry and the waste management organisations.

Roofing shingles account for most of the remaining asphalt consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Asphalt is used to make Japan black, a lacquer known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker.[86] Asphalt is also used to seal some alkaline batteries during the manufacturing process.

Typical asphalt plant for making asphalt

About 40,000,000 tons were produced in 1984.[needs update] It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as naphtha, gasoline and diesel). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude asphalt is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This step makes the product harder and more viscous.[5]

Asphalt is typically stored and transported at temperatures around 150 °C (302 °F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.

Main article: Oil sands

Naturally occurring crude bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from "oil sands", currently under development in Alberta, Canada. Canada has most of the world's supply of natural bitumen, covering 140,000 square kilometres[14] (an area larger than England), giving it the second-largest proven oil reserves in the world. The Athabasca oil sands are the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods. Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020.[15] The total amount of crude bitumen in Alberta that could be extracted is estimated to be about 310 billion barrels (50×10^9 m3),[8] which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.

Main articles: Peak oil, Global warming, and Bioasphalt

Although uncompetitive economically, asphalt can be made from nonpetroleum-based renewable resources such as sugar, molasses and rice, corn and potato starches. Asphalt can also be made from waste material by fractional distillation of used motor oil, which is sometimes otherwise disposed of by burning or dumping into landfills. Use of motor oil may cause premature cracking in colder climates, resulting in roads that need to be repaved more frequently.[87]

Nonpetroleum-based asphalt binders can be made light-colored. Lighter-colored roads absorb less heat from solar radiation, reducing their contribution to the urban heat island effect.[88] Parking lots that use asphalt alternatives are called green parking lots.

Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania, the only European asphalt mine still in use. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring and ball) around 120 °C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.

Albanian bitumen extraction has a long history and was practiced in an organized way by the Romans. After centuries of silence, the first mentions of Albanian bitumen appeared only in 1868, when the Frenchman Coquand published the first geological description of the deposits of Albanian bitumen. In 1875, the exploitation rights were granted to the Ottoman government and in 1912, they were transferred to the Italian company Simsa. Since 1945, the mine was exploited by the Albanian government and from 2001 to date, the management passed to a French company, which organized the mining process for the manufacture of the natural bitumen on an industrial scale.[89]

Today the mine is predominantly exploited in an open pit quarry but several of the many underground mines (deep and extending over several km) still remain viable. Selenizza is produced primarily in granular form, after melting the bitumen pieces selected in the mine.

Selenizza[90] is mainly used as an additive in the road construction sector. It is mixed with traditional asphalt to improve both the viscoelastic properties and the resistance to ageing. It may be blended with the hot asphalt in tanks, but its granular form allows it to be fed in the mixer or in the recycling ring of normal asphalt plants. Other typical applications include the production of mastic asphalts for sidewalks, bridges, car-parks and urban roads as well as drilling fluid additives for the oil and gas industry. Selenizza is available in powder or in granular material of various particle sizes and is packaged in sacks or in thermal fusible polyethylene bags.

A life-cycle assessment study of the natural selenizza compared with petroleum asphalt has shown that the environmental impact of the selenizza is about half the impact of the road asphalt produced in oil refineries in terms of carbon dioxide emission.[91]

People can be exposed to asphalt in the workplace by breathing in fumes or skin absorption. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit of 5 mg/m3 over a 15-minute period.[92]

Asphalt is basically an inert material that must be heated or diluted to a point where it becomes workable for the production of materials for paving, roofing, and other applications. In examining the potential health hazards associated with asphalt, the International Agency for Research on Cancer (IARC) determined that it is the application parameters, predominantly temperature, that affect occupational exposure and the potential bioavailable carcinogenic hazard/risk of the asphalt emissions.[93] In particular, temperatures greater than 199 °C (390 °F), were shown to produce a greater exposure risk than when asphalt was heated to lower temperatures, such as those typically used in asphalt pavement mix production and placement.[94] IARC has classified asphalt as a Class 2B possible carcinogen.

An asphalt mixing plant for hot aggregate
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