Bit concrete (commonly called asphalt , black dots , or sidewalks in North America, and asphalt or macadam bitumen or rolling asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used for road surfaces, parking lots, airports, and dam embankment core. It consists of mineral aggregates bonded together with asphalt, laid out in layers, and compacted. This process was refined and enhanced by Belgian inventor and US immigrant Edward de Smedt.
Asphaltic (or asphaltic) terms concrete , asphalt concrete
Video Asphalt concrete
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Asphalt and aggregate mixing is done in one of several ways:
- Hot-mix asphalt concrete (commonly abbreviated as HMA)
- It is produced by heating the asphalt binder to lower its viscosity, and drying the aggregate to remove moisture before mixing. Mixing is generally carried out with an aggregate of about 300 ° F (about 150 ° C) for virgin asphalt and 330 ° F (166 ° C) for asphalt polymer modification, and asphalt cement at 200 ° F (95 ° C). Ã, Â ° C). Paving and compacting should be done when the asphalt is hot enough. In many countries, paving is restricted to summer because in winter, the compacted base will cool the asphalt too much before it can be packed with the required density. HMA is the most common form of concrete asphalt used on high-traffic sidewalks such as on major highways, racetracks and airfields. It is also used as an environmental liner for landfills, reservoirs, and fish hatching ponds.
- A mixture of warm asphalt concrete (commonly abbreviated as WMA)
- This is generated by adding zeolites, waxes, asphalt emulsions, or sometimes even water to an asphalt binder before mixing. This allows significantly lower mixing and laying of temperatures and results in lower fossil fuel consumption, thereby releasing less carbon dioxide, aerosols, and steam. Not only are improved working conditions, but lower laying temperatures also lead to faster surface availability for use, which is critical for construction sites with critical time schedules. The use of these additives in hot asphalt mixtures (above) can result in easier compaction and allow for cooler weather paving or longer haulage. The use of warm mixture quickly developed. A survey of US asphalt producers found that nearly 25% of the asphalt produced in 2012 is a warm mix, a 416% increase since 2009.
- Mixture of cold asphalt concrete
- This is produced by emulsifying the asphalt in water with soap (essentially) before mixing with aggregate. While in emulsion conditions, 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 mixture will, ideally, take the nature of the HMA sidewalk. Cold blends are generally used as patch material and in the way of lower traded services.
- Cut-back asphalt concrete
- It is a form of cold mixed asphalt produced by dissolving binders in petroleum or lighter petroleum fractions before mixing with aggregates. While in a state of dissolved, the asphalt is less viscous and the mixture is easy to work and compact. After the mixture is placed, the lighter fraction will evaporate. Due to concerns with pollution from volatile organic compounds in lighter fractions, the cut-back asphalt has been largely replaced by asphalt emulsions.
- Asphalt concrete resin, or asphalt sheet
- This is produced by heating the hard blown asphalt (ie, partially oxidized) in the green cooker (mixer) until it becomes viscous liquid after the aggregate mixture is then added. The bitumen aggregate mix is ​​cooked (cooked) for about 6-8 hours and afterwards ready the mastic asphalt mixer is transferred to the workplace where the experienced layer empties the mixer and either the machine or hand puts the contents of the mastic asphalt onto the road. The resin asphalt concrete is generally placed in a thickness of about <2> 3 / 16 Ã, inch (20-30Ã, mm)) for path and road applications and about 3 / 8 inch (10 mm) for floor or roof applications.
- High-modulus asphalt concrete, sometimes called by the French acronym EMÃÆ' â € ° (enrobà © ÃÆ' module ÃÆ'  © levÃÆ'  ©)
- It uses very hard bituminous (10/20 penetration), sometimes modified, in proportion to approximately 6% in aggregate weight, and the proportion of mineral powder is also high, between 8-10%, to create an asphalt concrete layer with modulus of elasticity high, from orders of 13000 MPa, as well as a very high fatigue strength. The high modulus asphalt layer is used both in strengthening operations as well as in the construction of new reinforcements for moderate and heavy traffic. In the base layer, they tend to show greater capacity to absorb tension and, in general, better fatigue resistance.
In addition to asphalt and aggregates, additives, such as polymers, and antistripping agents may be added to improve the properties of the final product.
Sidewalk pavements - especially in the airfield - are sometimes called tarmacs for historical reasons, although they do not contain tar and are not built using macadam processes.
Various special asphalt concrete mixtures have been developed to meet special needs, such as rock-matrix asphalt, designed to ensure very strong wear surface, or bitumen asphalt, which permeable and allow water to flow through the sidewalk to control stormwater.
Maps Asphalt concrete
Performance characteristics
Different types of concrete asphalt have different performance characteristics in terms of surface durability, tire wear, braking efficiency and road noise. In principle, the determination of appropriate asphalt performance characteristics should take into account the volume of traffic in each vehicle category, and the performance requirements of the friction course.
Concrete asphalt produces less street noise than the Portland cement concrete surface, and is usually less noisy than the seal surface of the chip. Because the tire sound is generated through the conversion of kinetic energy to sound waves, more noise is generated when vehicle speed increases. The notion that the design of the highway might consider the consideration of acoustic techniques, including the selection of surface paving types, emerged in the early 1970s.
With regard to structural performance, asphalt behavior depends on various factors including material, loading and environmental conditions. Furthermore, the performance of the sidewalks varies from time to time. Therefore, long-term asphalt behavior differs from short-term performance. LTPP is a research program by FHWA, which specifically focuses on long-term pavement behavior.
Degradation and recovery
Asphalt deterioration may include cracked, perforated, turbulent, raveling, bleeding, rutting, pushing, stripping, and grade depressions. In cold climates, the frost can break the asphalt even in one winter. Filling the gap with asphalt is a temporary improvement, but only proper compaction and drainage can slow down this process.
The factors that cause asphalt concrete to deteriorate over time largely fall into one of three categories: construction quality, environmental considerations, and traffic load. Often, damage results from a combination of factors in all three categories.
Quality of construction is essential for pavement performance. This includes the construction of trenches and utility equipment placed on the sidewalk after construction. The lack of solidification on the asphalt surface, especially in longitudinal joints can reduce the life of a pavement by 30 to 40%. The trench service on the sidewalk after construction has been said to reduce the age of the pavement by 50%, mainly due to the lack of compaction in the trenches, and also because of water intrusion through unsealed connections.
Environmental factors include heat and cold, the presence of water in subbase ground or underlying ground sidewalks, and frost.
High temperatures soften asphalt binder, allowing heavy tire loads to damage the sidewalks into ruts. Paradoxically, high heat and strong sunlight also cause the asphalt to oxidize, become stiff and less resilient, leading to the formation of cracks. Cold temperatures can cause cracks due to asphalt contracts. The cold asphalt is also less tough and more vulnerable to cracking.
Water trapped beneath the sidewalk softens subbase and subgrade, making roads more vulnerable to traffic loads. The water below the road freezes and expands in cold weather, causing and enlarging cracks. In the spring melt, the soil melts from top to bottom, so water is trapped between the sidewalk above and the still frozen ground beneath it. This saturated soil layer provides little support for the path above, leading to the formation of a hole. This is more of a problem for muddy soil or clay than sandy or pebbly soil. Some jurisdictions pass a frozen weather law to reduce the weight of trucks allowed during the spring liquefaction season and protect their path.
The damage caused by the vehicle is proportional to the axle load that is raised to the fourth power, so doubling the weight carried on the axle actually causes 16 times more damage. The wheels cause the path to flex slightly, resulting in tired cracks, which often cause cracked crocodiles. The speed of the vehicle also plays a role. Slowly moving the vehicle emphasizes the road for longer periods of time, increasing the ruts, cracks, and snoring on the pavement sidewalk.
Other causes of damage include heat damage from vehicle fires, or solvent action from chemical spills.
Prevention and repair of degradation
The road life can be extended through good design, construction and maintenance practices. During the design, the engineers measure traffic on the road, paying particular attention to the number and type of trucks. They also evaluate the layers of the soil to see how much weight it can bear. The thickness of the sidewalk and subbase is designed to hold the wheel load. Sometimes, geogrid is used to strengthen the subbase and strengthen the path. Drainage, including trenches, storm drains, and underwater channels is used to move water from roads, preventing them from weakening subbase and soil layers.
Good maintenance practices center on keeping water out of the sidewalk, subbase and subsoil. Maintaining and cleaning storm ditches and ducts will extend the life of the road at a low cost. Sealing a small crack with a bituminous crack sealer prevents water from enlarging cracks through weathering frozen weather, or seeping down into the subbase and softening it.
For somewhat more depressed roads, chip seals or similar surface treatments may be applied. As the number, width and length of cracks increases, more intensive repairs are needed. In order to increase costs in general, this includes a thin layer of asphalt, multicourse overlay, milling on the top lane and overlaying, on-site recycling, or in-depth road reconstruction.
Much cheaper to keep the road in good shape than to fix it after his condition worsened. This is why some agencies place priority on preventive maintenance of roads in good condition, rather than reconstructing roads in poor conditions. Bad roads are improved because resources and budgets allow. In terms of lifetime costs and long-term pavement conditions, this will result in better system performance. Institutions that concentrate on restoring their bad paths often find that by the time they have repaired everything, roads that are in good condition have deteriorated.
Some agencies use pavement management systems to help prioritize maintenance and repairs.
Recycle
Asphalt concrete is 100% recyclable and is the most reusable construction material in the world. Very few concrete asphalt - less than 1 percent, according to a 2011 survey by the Federal Highway Administration and the National Asphalt Pavement Association - was actually dumped in landfills.
There is large scale asphalt recycling (known as on-site asphalt recycling or asphalt recycling in hot mixed plants) and asphalt recycling on a smaller scale. For small-scale asphalt recycling, users separate asphalt materials into three different categories:
- Blacktop Cookie
- Unmixed mixed asphalt mixture pieces that can be used for hole repairs. The use of blacktop cookies has been investigated as a cheaper, less labor-intensive, longer-lasting alternative to repairing holes with cold patches. In a program in Pittsfield, Massachusetts, workers bought new hot mix asphalt and spread it freely on the ground to produce about 25 pounds of wafers. Once cooled, the wafers can be stored until they are heated in a hot box to make small road repairs. Blacktop cookies can also be produced from waste materials from paving work.
- Asphalt road reclamation (RAP)
- The asphalt cuts that have been removed from the road, parking lot or driveway are considered as asphalt pavement (RAP). These asphalt pieces are usually torn when making regular asphalt repairs, human hole repairs, basin repairs or major sewer repairs. Since the asphalt has been compacted, RAP is a solid asphalt material and usually takes longer to be recycled than the blacktop cookie.
- Asphalt millings
- Small pieces of asphalt produced by a mechanically grounded asphalt surface are referred to as bitumen asphalt. Large millings that have rich black color show high cement asphalt content is best for asphalt recycling purposes. Millings surfaces are recommended over full deep millings when choosing asphalt milling for recycling. Full depth work usually contains sub-basic contaminants such as gravel, mud and sand. These sub-contaminants will seep oil from the original asphalt and dry the material in the recycling process. Asphalt milled from asphalt is better than asphalt that is milled from concrete. When processing the asphalt from the concrete, the resulting dust is not compatible with asphalt products because it is not asphalted.
Small scale asphalt recycling will typically involve high-speed asphalt recycling equipment in place or recycling soft asphalt overnight.
Small-scale asphalt recycling is used when making smaller road repairs compared to large scale asphalt recycling done to make new asphalt or to remove old asphalt and at the same time recycle/replace asphalt. Recycled asphalt is very effective for repairing potholes and utilities. Recycled asphalt will usually last longer or longer from the surrounding road because new asphalt cement has been added back to the material.
For large-scale asphalt recycling, some on-site recycling techniques have been developed to rejuvenate oxidized oxidizers and eliminate cracks, although recycled materials are generally not very water-resistant or smooth and should be coated with a new layer of asphalt concrete. Recycling plant in a cool place from the top layer of concrete asphalt and mix loose milling results with asphalt emulsion. The mixture is then placed back on the road and compacted. The water in the emulsion is allowed to evaporate for a week or more, and new hot-mix asphalt is placed on top of it.
The asphalt concrete removed from the sidewalk is usually dumped for use as an aggregate for a new hot mix asphalt in an asphalt plant. This reclaimed material, or RAP, is destroyed into a consistent gradation and added to the HMA mixing process. Sometimes waste materials, such as asphalt roofing, broken glass, or rubber from scrap tires, are added to asphalt concrete as is the case with rubber asphalt, but there is a concern that hybrid materials may not be recycled.
See also
References
External links
- Association of National Asphalt Pavilion
- Asphalt Pavement Alliance
- Asphalt Education Partnership
- Common type of asphalt pressure
Source of the article : Wikipedia
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