ASPHALT

fact 7Asphalt pavement is a high-quality, thoroughly controlled, engineered material made from aggregates (stone, sand or gravel) using asphalt cement as a binder. Asphalt pavement is made by heating asphalt cement and mixing it fact  1with aggregates and mineral fillers. The asphalt mixture is loaded immediately onto trucks for delivery to construction sites or kept in storage silos.

Asphalt pavement material begins to cool as soon as it is mixed. In order to maintain workability at the paving site, and for the highest quality of the finished pavement, the mixing facility (asphalt plant) must be near the paving site.

fact 3
The History of Asphalt

The story of asphalt begins thousands of years before the founding of the United States. Asphalt occurs naturally in both asphalt lakes and in rock asphalt (a mixture of sand, limestone and asphalt).

fact 2The ancient Mesopotamians used it to waterproof temple baths and water tanks. The Phoenicians caulked the seams of their merchant ships with asphalt. In the days of the Pharaohs, Egyptians used the material as mortar for rocks laid along the banks of the Nile to prevent erosion, and the infant Moses' basket was waterproofed with asphalt.

625 B.C.
The first recorded use of asphalt as a road-building material in Babylon. The ancient Greeks were also familiar with asphalt. The word asphalt comes from the Greek "asphaltos," meaning "secure." The Romans used it to seal their baths, reservoirs and aqueducts.

1595
Europeans exploring the New World discovered natural deposits of asphalt. Sir Walter Raleigh described a "plain" (or lake) of asphalt on the island of Trinidad, near Venezuela. He used it for re-caulking his ships.

Early 1800s
Thomas Telford built more than 900 miles of roads in Scotland, perfecting the method of building roads with broken stones. His contemporary, John Loudon McAdam, used broken stone joined to form a hard surface to build a Scottish turnpike. Later, to reduce dust and maintenance, builders used hot tar to bond the broken stones together, producing "tarmacadam" pavements.

1870
Belgian chemist Edmund J. DeSmedt laid the first true asphalt pavement in the U.S. in Newark, N.J. DeSmedt also paved Pennsylvania Avenue in Washington, D.C. – using 54,000 square yards of sheet asphalt from Trinidad Lake. The Cummer Company opened the first central hot mix production facilities in the U.S. The first asphalt patent was filed by Nathan B. Abbott of Brooklyn, N.Y. in 1871.

1900
Frederick J. Warren filed a patent for "Bitulithic" pavement, a mixture of bitumen and aggregate ("bitu" from "bitumen" and "lithic" from "lithos," the Greek word for rock). The first modern asphalt facility was built in 1901 by Warren Brothers in East Cambridge, Mass.

1907
Production of refined petroleum asphalt outstripped the use of natural asphalt. As automobiles grew in popularity, the demand for more and better roads led to innovations in both producing and laying asphalt. Steps toward mechanization included drum mixers and portland cement concrete mechanical spreaders for the first machine-laid asphalt.

1942
During World War II, asphalt technology greatly improved, spurred by the need of military aircraft for surfaces that could stand up to heavier loads.

1955
The National Bituminous Concrete Association (forerunner of the National Asphalt Pavement Association or NAPA) was founded. One of the first activities: a Quality Improvement Program, which sponsored asphalt testing at universities and private testing labs.

1956
Congress passed the Interstate Highways Act, allotting $51 billion to the states for road construction. Contractors needed bigger and better equipment. Innovations since then include electronic leveling controls, extra-wide finishers for paving two lanes at once and vibratory steel-wheel rollers.

1970s
The national energy crisis underscored the need for conservation of natural resources. Since that time, an increasing amount of recycled asphalt has been incorporated in mixes. Today, asphalt pavement is America's most recycled material with more than 70 million metric tons of asphalt paving material is recycled each year.

1986
NAPA established the National Center for Asphalt Technology (NCAT) at Auburn University, Alabama, providing a centralized, systematic approach to asphalt research. NCAT recently opened a new research center and test track and is now the world's leading institution for asphalt pavement research.

2002
The EPA announced that asphalt plants are no longer on its list of industries considered major sources of hazardous air pollutants.

 

How Asphalt is Usedfact 4

Other uses for asphaltThe first thing that comes to mind when you hear asphalt is roads. But the versatility of asphalt makes it the ideal material for other applications and locations: from driveways to runways, from the barn floor to the ocean floor.

HMA is also used worldwide as a practical solution to water storage, flood control, erosion, and conservation problems. Asphalt has been approved by the Environmental Protection Agency and used successfully as a primary liner for both sanitary and hazardous waste landfills.

You'll find asphalt all around you in a variety of uses, including:

 

ENVIRONMENTAL STANDARDS

fact 5Asphalt plants must meet rigorous standards established by the EPA and other agencies, but often the individual plants set their own standards that are even more demanding. Recent improvements in asphalt production have made the industry even more environmentally friendly. In fact, after a six-year study, the EPA announced in 2002 that asphalt plants are no longer on its list of industries considered major sources of hazardous air pollutants.

Asphalt pavement is 100 percent recyclable and can be made to perform better the second or even third time around. In fact, it is the most recycled product in the United States, both in terms of tonnage (73 million tons, more than any other material) and in terms of percentage (80 percent of reclaimed asphalt fact 8pavement is recycled, a higher percentage than any other substance). That compares to significantly lower percentages for aluminum cans, newsprint, plastic and glass beverage containers, and magazines. Asphalt roads are removed, recrushed, mixed with additional aggregate and fresh asphalt cement, remixed and placed back on the road. The hot mix asphalt industry also uses the following recycled materials: slag from the steel-making process, roofing shingles, sand from metal-casting foundries, and rubber from old tires.

* In a joint report to Congress, the Federal Highway Administration and the Environmental Protection Agency estimated that more than 73 million tons of asphalt paving material was recycled in 1992.
* Recycling roads not only conserves natural resources and decreases construction time, it saves American taxpayers more than $300 million each year.

Asphalt pavements can be designed and constructed for maximum skid resistance. Research has shown that asphalt roads tend to be quieter than concrete roads, leading to less driver fatigue. Other safety features of asphalt:

* Asphalt is impervious to de-icing salts and chemicals and is unaffected by winter road safety maintenance.
* Asphalt pavements can be designed with "open-graded" surfaces that allow water to drain through the surface layer of the pavement, thus reducing splash and tire spray, and increasing tire-road contact during wet weather.

In addition to its recyclability, which conserves precious natural resources, asphalt provides long-life solutions for pavement construction. Some asphalt pavements reduce noise pollution and alleviate other environmental concerns. And, while annual production of asphalt paving material has increased by more than 250 percent over the past 40 years, emissions from asphalt plants have dropped by 97 percent or more. Some additional points to consider:fact 6

* Asphalt is not soluble or harmful in a water environment. It has been used successfully for many years in fish hatcheries, reservoirs of drinking water for human consumption, and other environmental protection applications.
* Asphalt prevents pollution from getting into water supplies and protects against disease from waste materials. It can be combined with aggregate to form a voidless and impermeable layer. Asphalt pavements are effective liners and caps for landfills.
* Many states have tested discarded asphalt pavement and determined that it should be categorized as clean fill.

Well-designed, well-built asphalt pavements last many years. For instance, the asphalt portions of Interstate 90 in Washington State have been in place since their original construction more than 35 years ago with no rehabilitation for structural reasons. The entire New Jersey Turnpike is asphalt. Built in 1951, it has never had a failure in the pavement structure. The chief engineer for the turnpike expects it to last another 50 years.

Called the "perpetual pavement," asphalt pavements can last a lifetime because it's possible to maintain them with only periodic replacement of the surface layer. And with the newer heavy-duty surface pavements, it is possible for overlays to last more than 15 to 20 years.

Numerous studies in the U.S. and Europe have shown that asphalt pavements generally have a lower life cycle cost. The initial cost of asphalt pavement is usually less than concrete. In addition, an increasingly important factor is the traffic delay cost during construction or rehabilitation. You can't close down a busy road and spend weeks repairing it without costing businesses and individuals money – potentially millions of dollars. With asphalt, you can usually perform construction and rehabilitation operations at night and reopen the road to traffic the next

SAFETY

Asphalt pavements can be designed and constructed for maximum skid resistance. Research has shown that asphalt roads tend to be quieter than concret roads, leading to less driver fatigue.

Asphalt is impervious to de-icing salts and chemicals and is unaffected by winter road safety maintenance. Asphalt pavements can be designed with "open-graded" surfaces that allow water to drain through the surface layer of the payment, thus reducing splash and tire spray, and increasing tire-road contact during wet weather. In other words, less hydro-planing!

Other benefits to the driver are better roads increased gas mileage, reduced vehicle maintenance costs, and prolonged life of tires.

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