grlcorp.com
|
Finaltouchontheweb.com Funwheelshonda.net Gemaginations.com Goldofeldorado.com Greekcrucifix.com Grupoconvivir.com Guiascouts.com Guiasscouts.com Gujarati.com |
| grlcorp.com | Brick a ceramic block | Architectural glass | Tempered Glass | Asphalt concrete | Concrete and aggregate | Portland cement | Types of Portland cement |
Asphalt concrete
|
Asphalt concrete, normally known simply as asphalt, is a composite
material commonly used for construction of pavement, highways and
parking lots. It consists of asphalt binder and mineral aggregate
mixed together then laid down in layers and compacted. Mixing of asphalt and aggregate is accomplished in one of several ways: Hot Mix Asphalt Concrete (commonly abbreviated as HMAC) is produced by heating the asphalt in order to decrease its viscosity and drying the aggregate to remove moisture from it prior to mixing. Mixing is generally performed at about 160 degrees Celsius, while paving and compaction are performed at about 140 degrees Celsius. HMAC is the form of asphalt concrete most commonly used on highly trafficked pavements such as those on major highways and airfields. |
|
|
Warm Mix Asphalt Concrete (commonly abbreviated as WMA or WAM) is
produced by adding either zeolites, waxes, or asphalt emulsions to
the mix. This allows significantly lower mixing and laying
temperatures and results in lower consumption of fossil fuels, thus
releasing less carbon dioxide, aerosols and vapours. Not only are
working conditions clearly improved, but the lower
laying-temperature also leads to more rapid availability of the
surface for use (in construction sites with critical time
schedules). Cold Mix Asphalt Concrete 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 cold HMAC. Cold mix is commonly used as a patching material and on lesser trafficked service roads. Cut-back Asphalt Concrete is 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. Due to the resulting air pollution cut-backs have been illegal in the US since the 1970s. They are still widely used in Europe and the rest of the world, especially for recycling old asphalt pavement. 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. Natural asphalt concrete can be found in some parts of the world where rock near the surface has been impregnated with upwelling asphalt. The term asphalt concrete is typically only used in engineering jargon. It is often called just asphalt by laypersons who tend to associate the term concrete with portland cement concrete only. The engineering definition of concrete is any composite material composed of mineral aggregate stuck together with a binder, whether that binder is portland cement, asphalt or even epoxy. Asphalt concrete is often touted as being 100% Recyclable. 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. Asphalt concrete that is removed from a pavement is usually stockpiled for later use as a base course material. Very little asphalt concrete is actually disposed of in landfills. Sometimes waste materials, such as rubber from old tires, are added to asphalt concrete but there is a concern that the hybrid material may not be recyclable. 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. Asphalt is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits. Asphalt is composed almost entirely of bitumen. There is some disagreement amongst chemists regarding the structure of asphalt, however it is most commonly modeled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase. Asphalt is sometimes confused with tar, which is an artificial material produced by the destructive distillation of organic matter. Tar is also predominantly composed of bitumen, however the bitumen content of tar is typically lower than that of asphalt. Tar and asphalt have very different engineering properties. Asphalt can be separated from the other components in crude oil (such as naphtha, gasoline and diesel) by the process of fractional distillation, usually under vacuum conditions. A better separation can be achieved by further processing of the heavier fractions of the crude oil in a de-asphalting unit which uses either propane or butane in a supercritical phase to dissolve the lighter molecules which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This makes the product harder and more viscous. Natural deposits of asphalt include Lake Asphalts (primarily from the Pitch Lake in Trinidad and Tobago and Bermudez Lake in Venezuela), Gilsonite, the Dead Sea in Israel, and Tar Sands. Asphalt is rather hard to transport in bulk (it hardens unless kept very hot) so it is sometimes mixed with diesel oil or kerosene before shipping. Upon delivery, these lighter materials are separated out of the mixture. This mixture is often called bitumen feedstock, or BFS. The largest use of asphalt is for making asphalt concrete for pavements, which accounts for approximately 80% of the asphalt consumed in the United States. Roofing shingles account for most of the remaining asphalt consumption. Other uses include cattle sprays, fence post treatments, and waterproofing for fabrics. While Americans are accustomed to thinking about recycling their newspapers and beverage containers, the most widely recycled product in terms of both percentage and tonnage is actually asphalt pavement. According to a report issued by the Federal Highway Administration and the United States Environmental Protection Agency, 80 percent of the asphalt pavement that is removed each year during widening and resurfacing projects is reused as part of new roads, roadbeds, shoulders and embankments. In the ancient middle-east, natural asphalt deposits were used for mortar between bricks and stones, ship caulking, and waterproofing. The Persian word for asphalt is mumiya, which may be the source for the English word mummy. |
|
Nofeerentals.com Apartamentos para arrendar en Nueva York
Apartamentos para arrendar en Nueva York. Somos: Nofeerentals.com fue establecido al final de los 1980s para servir personas buscando apartamentos para ...
http://www.nofeerentals.com/Apartamentos-para-arrendar-en-Nueva-York.htm
Notasinc.com Filigree Cards, Colorful personal or business card for any occasion, hand made
Paper filigree technique (Quilling) hand made colorful personal or business cards. The perfect gift for birthdays, weddings, anniversaries, births, showers, thank you notes, business, or any occasion.
http://www.notasinc.com/filigree_cards.htm
Lansend.com: Microsoft Certified Computer consultants in New York, NY
Microsoft Certified Computer consultants providing computer and network consulting services in New York ,NY Manhattan Queens, Lan Wan Networking VPN.
http://www.lansend.com
Benefits of Drinking Tea
There are lots of reasons I enjoy a hot cup of tea: I love the aroma of various
flavors of tea; holding onto a hot tea mug warms my hands on a cold winter ...
http://www.quiktea.com/catalog/Benefits_of_Drinking_Tea-14-1.html
| grlcorp.com | Brick a ceramic block | Architectural glass | Tempered Glass | Asphalt concrete | Concrete and aggregate | Portland cement | Types of Portland cement |