How Do You Select The Best Driveway or Driveway Pavers?
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 Pavers in Sandton 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.
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.
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.
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.
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). 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.” Other areas may prohibit leaving vehicles on residential streets during certain times (for instance, to accommodate regular street cleaning), necessitating the use of driveways.
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.
Interesting Facts About Driveway Pavers in Rivonia:
About Driveway Pavers in Rivonia:Asphalt batch mix plant A machine laying asphalt concrete, fed from a dump truck
Asphalt concrete (commonly called asphalt, 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. 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.
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: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. 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. 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. 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. 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.
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.
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. 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.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, 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.
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.
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. 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.
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.
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.
Driveway Pavers in RivoniaRaised 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, as well as parts of the Mid-Atlantic United States such as Philadelphia and New Jersey. 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".
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. "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.
In the UK, the term "footpath" is mostly used for paths that do not abut a roadway. The term "shared-use path" is used where cyclists are also able to use the same section of path as pedestrians.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.
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.
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. 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. 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.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% 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%. 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.
The presence or absence of sidewalks was one of three factors that were found to encourage drivers to choose lower, safer speeds.
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.
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. 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.
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. Also, children who walk to school have been shown to have better concentration.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. 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. When quantities of Portland cement were first imported to the United States in the 1880s, its principal use was in the construction of sidewalks.
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. 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.
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.
Boulevard(Redirected from Asphalt pavement) A road being resurfaced
A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, cobblestone and granite setts were extensively used, but these surfaces have mostly been replaced by asphalt or concrete laid on a compacted base course. Road surfaces are frequently marked to guide traffic. Today, permeable paving methods are beginning to be used for low-impact roadways and walkways. Pavements are crucial to countries such as US and Canada, which heavily depend on road transportation. Therefore, research projects such as Long-Term Pavement Performance are launched to optimize the life-cycle of different road surfaces.Red surfacing for the bicycle lane in the Netherlands Closeup of asphalt on a driveway
Asphalt (specifically, asphalt concrete), sometimes called flexible pavement due to the nature in which it distributes loads, has been widely used since the 1920s. The viscous nature of the bitumen binder allows asphalt concrete to sustain significant plastic deformation, although fatigue from repeated loading over time is the most common failure mechanism. Most asphalt surfaces are laid on a gravel base, which is generally at least as thick as the asphalt layer, although some 'full depth' asphalt surfaces are laid directly on the native subgrade. In areas with very soft or expansive subgrades such as clay or peat, thick gravel bases or stabilization of the subgrade with Portland cement or lime may be required. Polypropylene and polyester geosynthetics have also been used for this purpose and in some northern countries, a layer of polystyrene boards have been used to delay and minimize frost penetration into the subgrade.
Depending on the temperature at which it is applied, asphalt is categorized as hot mix, warm mix, or cold mix. Hot mix asphalt is applied at temperatures over 300 °F (150 °C) with a free floating screed. Warm mix asphalt is applied at temperatures of 200–250 °F (95–120 °C), resulting in reduced energy usage and emissions of volatile organic compounds. Cold mix asphalt is often used on lower-volume rural roads, where hot mix asphalt would cool too much on the long trip from the asphalt plant to the construction site.
An asphalt concrete surface will generally be constructed for high-volume primary highways having an average annual daily traffic load greater than 1200 vehicles per day. Advantages of asphalt roadways include relatively low noise, relatively low cost compared with other paving methods, and perceived ease of repair. Disadvantages include less durability than other paving methods, less tensile strength than concrete, the tendency to become slick and soft in hot weather and a certain amount of hydrocarbon pollution to soil and groundwater or waterways.
In the mid-1960s, rubberized asphalt was used for the first time, mixing crumb rubber from used tires with asphalt. While a potential use for tires that would otherwise fill landfills and present a fire hazard, rubberized asphalt has shown greater incidence of wear in freeze-thaw cycles in temperate zones due to non-homogeneous expansion and contraction with non-rubber components. The application of rubberized asphalt is more temperature-sensitive, and in many locations can only be applied at certain times of the year.
Study results of the long-term acoustic benefits of rubberized asphalt are inconclusive. Initial application of rubberized asphalt may provide 3–5 decibels (dB) reduction in tire-pavement source noise emissions; however, this translates to only 1–3 decibels (dB) in total traffic noise level reduction (due to the other components of traffic noise). Compared to traditional passive attenuating measures (e.g., noise walls and earth berms), rubberized asphalt provides shorter-lasting and lesser acoustic benefits at typically much greater expense.Concrete roadway in San Jose, California Further information: Concrete
Concrete surfaces (specifically, Portland cement concrete) are created using a concrete mix of Portland cement, coarse aggregate, sand and water. In virtually all modern mixes there will also be various admixtures added to increase workability, reduce the required amount of water, mitigate harmful chemical reactions and for other beneficial purposes. In many cases there will also be Portland cement substitutes added, such as fly ash. This can reduce the cost of the concrete and improve its physical properties. The material is applied in a freshly mixed slurry, and worked mechanically to compact the interior and force some of the cement slurry to the surface to produce a smoother, denser surface free from honeycombing. The water allows the mix to combine molecularly in a chemical reaction called hydration.A concrete road in Ewing, New Jersey. The original pavement was laid in the 1950s and has not been significantly altered since.
Concrete surfaces have been refined into three common types: jointed plain (JPCP), jointed reinforced (JRCP) and continuously reinforced (CRCP). The one item that distinguishes each type is the jointing system used to control crack development.
One of the major advantages of concrete pavements is they are typically stronger and more durable than asphalt roadways. They also can be grooved to provide a durable skid-resistant surface. A notable disadvantage is that they typically can have a higher initial cost, and can be more time-consuming to construct. This cost can typically be offset through the long life cycle of the pavement. Concrete pavement can be maintained over time utilizing a series of methods known as concrete pavement restoration which include diamond grinding, dowel bar retrofits, joint and crack sealing, cross-stitching, etc. Diamond grinding is also useful in reducing noise and restoring skid resistance in older concrete pavement.
The first street in the United States to be paved with concrete was Court Avenue in Bellefontaine, Ohio in 1893. The first mile of concrete pavement in the United States was on Woodward Avenue in Detroit, Michigan in 1909. Following these pioneering uses, the Lincoln Highway Association, established in October 1913 to oversee the creation of one of the United States' earliest east-west transcontinental highways for the then-new automobile, began to establish "seedling miles" of specifically concrete-paved roadbed in various places in the American Midwest, starting in 1914 west of Malta, Illinois, while using concrete with the specified concrete "ideal section" for the Lincoln Highway in Lake County, Indiana during 1922 and 1923.An example of composite pavement: hot-mix asphalt overlaid onto Portland cement concrete pavement
Composite pavements combine a Portland cement concrete sublayer with an asphalt. They are usually used to rehabilitate existing roadways rather than in new construction.
Asphalt overlays are sometimes laid over distressed concrete to restore a smooth wearing surface. A disadvantage of this method is that movement in the joints between the underlying concrete slabs, whether from thermal expansion and contraction, or from deflection of the concrete slabs from truck axle loads, usually causes reflective cracks in the asphalt. To decrease reflective cracking, concrete pavement is broken apart through a break and seat, crack and seat, or rubblization process. Geosynthetics can be used for reflective crack control. With break and seat and crack and seat processes, a heavy weight is dropped on the concrete to induce cracking, then a heavy roller is used to seat the resultant pieces into the subbase. The main difference between the two processes is the equipment used to break the concrete pavement and the size of the resulting pieces. The theory is frequent small cracks will spread thermal stress over a wider area than infrequent large joints, reducing the stress on the overlying asphalt pavement. Rubblization is a more complete fracturing of the old, worn-out concrete, effectively converting the old pavement into an aggregate base for a new asphalt road.
Whitetopping uses Portland cement concrete to resurface a distressed asphalt road.An asphalt milling machine in Boise, Idaho.
Distressed road materials can be reused when rehabilitating a roadway. The existing pavement is ground or broken up into small pieces, through a process called milling. It can then be transported to an asphalt or concrete plant and incorporated into new pavement, or recycled in place to form the base or subbase for new pavement. Some methods used include:Main article: Chipseal
Bituminous surface treatment (BST) or chipseal is used mainly on low-traffic roads, but also as a sealing coat to rejuvenate an asphalt concrete pavement. It generally consists of aggregate spread over a sprayed-on asphalt emulsion or cut-back asphalt cement. The aggregate is then embedded into the asphalt by rolling it, typically with a rubber-tired roller. This type of surface is described by a wide variety of regional terms including "chip seal", "tar and chip", "oil and stone", "seal coat", "sprayed seal" or "surface dressing" or as simply "bitumen."
BST is used on hundreds of miles of the Alaska Highway and other similar roadways in Alaska, the Yukon Territory, and northern British Columbia. The ease of application of BST is one reason for its popularity, but another is its flexibility, which is important when roadways are laid down over unstable terrain that thaws and softens in the spring.
Other types of BSTs include micropaving, slurry seals and Novachip. These are laid down using specialized and proprietary equipment. They are most often used in urban areas where the roughness and loose stone associated with chip seals is considered undesirable.
A thin membrane surface (TMS) is an oil-treated aggregate which is laid down upon a gravel road bed, producing a dust-free road. A TMS road reduces mud problems and provides stone-free roads for local residents where loaded truck traffic is negligible. The TMS layer adds no significant structural strength, and so is used on secondary highways with low traffic volume and minimal weight loading. Construction involves minimal subgrade preparation, following by covering with a 50-to-100-millimetre (2.0–3.9 in) cold mix asphalt aggregate. The Operation Division of the Ministry of Highways and Infrastructure in Saskatchewan has the responsibility of maintaining 6,102 kilometres (3,792 mi) of thin membrane surface (TMS) highways.
Otta seal is a low-cost road surface using a 16–30-millimetre (0.63–1.18 in) thick mixture of bitumen and crushed rock.Main article: Gravel road
Gravel is known to have been used extensively in the construction of roads by soldiers of the Roman Empire (see Roman road) but in 1998 a limestone-surfaced road, thought to date back to the Bronze Age, was found at Yarnton in Oxfordshire, Britain. Applying gravel, or "metalling," has had two distinct usages in road surfacing. The term road metal refers to the broken stone or cinders used in the construction or repair of roads or railways, and is derived from the Latin metallum, which means both "mine" and "quarry". The term originally referred to the process of creating a gravel roadway. The route of the roadway would first be dug down several feet and, depending on local conditions, French drains may or may not have been added. Next, large stones were placed and compacted, followed by successive layers of smaller stones, until the road surface was composed of small stones compacted into a hard, durable surface. "Road metal" later became the name of stone chippings mixed with tar to form the road surfacing material tarmac. A road of such material is called a "metalled road" in Britain, a "paved road" in Canada and the US, or a "sealed road" in parts of Canada, Australia and New Zealand.
A granular surface can be used with a traffic volume where the annual average daily traffic is 1,200 vehicles per day or less. There is some structural strength if the road surface combines a sub base and base and is topped with a double graded seal aggregate with emulsion. Besides the 4,929 kilometres (3,063 mi) of granular pavements maintained in Saskatchewan, around 40% of New Zealand roads are unbound granular pavement structures.
The decision whether to pave a gravel road or not often hinges on traffic volume. It has been found that maintenance costs for gravel roads often exceed the maintenance costs for paved or surface-treated roads when traffic volumes exceed 200 vehicles per day.
Some communities are finding it makes sense to convert their low-volume paved roads to aggregate surfaces.
Pavers (or paviours), generally in the form of pre-cast concrete blocks, are often used for aesthetic purposes, or sometimes at port facilities that see long-duration pavement loading. Pavers are rarely used in areas that see high-speed vehicle traffic.
Brick, cobblestone, sett, wood plank, and wood block pavements such as Nicolson pavement, were once common in urban areas throughout the world, but fell out of fashion in most countries, due to the high cost of labor required to lay and maintain them, and are typically only kept for historical or aesthetic reasons. In some countries, however, they are still common in local streets. In the Netherlands, brick paving has made something of a comeback since the adoption of a major nationwide traffic safety program in 1997. From 1998 through 2007, more than 41,000 km of city streets were converted to local access roads with a speed limit of 30 km/h, for the purpose of traffic calming. One popular measure is to use brick paving - the noise and vibration slows motorists down. At the same time, it is not uncommon for cycle paths alongside a road to have a smoother surface than the road itself.
Likewise, macadam and tarmac pavements can still sometimes[when?] be found buried underneath asphalt concrete or Portland cement concrete pavements, but are rarely[clarification needed] constructed today[when?].
There are also other methods and materials to create pavements that have appearance of brick pavements. The first method to create brick texture is to heat an asphalt pavement and use metal wires to imprint a brick pattern using a compactor to create stamped asphalt. A similar method is to use rubber imprinting tools to press over a thin layer of cement to create decorative concrete. Another method is to use a brick pattern stencil and apply a surfacing material over the stencil. Materials that can be applied to give the color of the brick and skid resistance can be in many forms. An example is to use colored polymer-modified concrete slurry which can be applied by screeding or spraying. Another material is aggregate-reinforced thermoplastic which can be heat applied to the top layer of the brick-pattern surface. Other coating materials over stamped asphalt are paints and two-part epoxy coating.
Roadway surfacing choices are known to affect the intensity and spectrum of sound emanating from the tire/surface interaction. Initial applications of noise studies occurred in the early 1970s. Noise phenomena are highly influenced by vehicle speed.
Roadway surface types contribute differential noise effects of up to 4 dB, with chip seal type and grooved roads being the loudest, and concrete surfaces without spacers being the quietest. Asphaltic surfaces perform intermediately relative to concrete and chip seal. Rubberized asphalt has been shown to give a marginal 3–5 dB reduction in tire-pavement noise emissions, and a marginally discernible 1–3 dB reduction in total road noise emissions when compared to conventional asphalt applications.See also: Pothole, Crocodile cracking, Rut (roads), and Bleeding (roads) Deteriorating asphalt
As pavement systems primarily fail due to fatigue (in a manner similar to metals), the damage done to pavement increases with the fourth power of the axle load of the vehicles traveling on it. According to the AASHO Road Test, heavily loaded trucks can do more than 10,000 times the damage done by a normal passenger car. Tax rates for trucks are higher than those for cars in most countries for this reason, though they are not levied in proportion to the damage done. Passenger cars are considered to have little practical effect on a pavement's service life, from a materials fatigue perspective.
Other failure modes include aging and surface abrasion. As years go by, the binder in a bituminous wearing course gets stiffer and less flexible. When it gets "old" enough, the surface will start losing aggregates, and macrotexture depth increases dramatically. If no maintenance action is done quickly on the wearing course, potholes will form. The freeze-thaw cycle in cold climates will dramatically accelerate pavement deterioration, once water can penetrate the surface.
If the road is still structurally sound, a bituminous surface treatment, such as a chipseal or surface dressing can prolong the life of the road at low cost. In areas with cold climate, studded tires may be allowed on passenger cars. In Sweden and Finland, studded passenger car tires account for a very large share of pavement rutting.
The physical properties of a stretch of pavement can be tested using a falling weight deflectometer.
Several design methods have been developed to determine the thickness and composition of road surfaces required to carry predicted traffic loads for a given period of time. Pavement design methods are continuously evolving. Among these are the Shell Pavement design method, and the American Association of State Highway and Transportation Officials (AASHTO) 1993 "Guide for Design of Pavement Structures". A new mechanistic-empirical design guide has been under development by NCHRP (Called Superpave Technology) since 1998. A new design guide called Mechanistic Empirical Pavement Design Guide (MEPDG) was developed and is about to be adopted by AASHTO.
Further research by University College London into pavements has led to the development of an indoor, 80-sq-metre artificial pavement at a research centre called Pedestrian Accessibility and Movement Environment Laboratory (PAMELA). It is used to simulate everyday scenarios, from different pavement users to varying pavement conditions. There also exists a research facility near Auburn University, the NCAT Pavement Test Track, that is used to test experimental asphalt pavements for durability.
In addition to repair costs, the condition of a road surface has economic effects for road users. Rolling resistance increases on rough pavement, as does wear and tear of vehicle components. It has been estimated that poor road surfaces cost the average US driver $324 per year in vehicle repairs, or a total of $67 billion. Also, it has been estimated that small improvements in road surface conditions can decrease fuel consumption between 1.8 and 4.7%.Main article: Road surface marking
Road surface markings are used on paved roadways to provide guidance and information to drivers and pedestrians. It can be in the form of mechanical markers such as cat's eyes, botts' dots and rumble strips, or non-mechanical markers such as paints, thermoplastic, plastic and epoxy.
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