Asphalt (also known as black top, hot mix asphalt "HMA", tarvey, macadem and tarmac) is a mixture of crushed rock (aggregates) and asphalt cement in specifically controlled amounts. Asphalt cement is a derivative of crude oil refining that is very heavy and thick. It is the glue that holds the aggregates together. This mixture is scientifically engineered and heated over 300 degrees so it can be placed and rolled to a smooth surface.
Asphalt covers 94 percent of the roads in the United States. It offers quick construction compared to other building materials. It creates a quieter ride that reduces driver fatigue, is smooth, durable, and skid resistant. Asphalt paving allows fewer construction delays and traffic congestion than other construction possibilities.
A pothole is caused by water penetrating the asphalt (often through a crack) and weakening the stone base during the freezing and thawing cycles of winter. Improper sub-grade (clay) can also contribute to potholes.
Asphalt has been around long before anyone was writing history books. It is found naturally in asphalt lakes and asphalt rocks. The word "asphalt" comes from the Greek "asphaltos," meaning "secure." In ancient times, it was used as a sealer for ships. The Mesopotamians used it to waterproof temple baths and water tanks. 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. In 625 B.C., asphalt was used to make a road in Babylon. The Romans used it to waterproof their aqueducts. Even today, asphalt is still being used to line water reservoirs in Western North America.
Yes. In fact, asphalt is the number one recycled material in the United States. Asphalt is recrushed and reused in new asphalt mix designs.
Yes. 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 the 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:
No. While both paving and roofing asphalts are derived from the petroleum refining process, they are used in very different ways. Asphalt used in roofing is typically a harder grade of asphalt that is heated to much higher temperatures than those used in paving operations.
The pavement is built in layers. The first step is to remove topsoil and compact the earth. Then, a base that will help to carry the load is placed and compacted. (The base may be constructed solely of stone, or it may include both stone and asphalt.) Then, two or more layers of hot mix asphalt are placed and compacted.
That’s an engineering decision, based on what kind of stresses the pavement must withstand (trucks vs. cars) and other factors such as soil conditions and climate. It also depends on what materials will be used in the asphalt and what materials might be present in the lower layers of the pavement.
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.
Aggregates are dried and heated, then mixed and coated with asphalt cement. After mixing, it is conveyed into storage silos where it is loaded onto trucks for delivery to a job site.
Our plants store fuel oil and gasoline in storage tanks that are either buried underground (like your local gas station) or above ground surrounded by berms that would hold all the contents in the event of a spill. These are strictly regulated by federal EPA and EGLE.
There is little concern if asphalt cement spills out of either a transporting vehicle or at a plant. It starts to harden the moment it cools to under 250 degrees F and cannot travel over the ground more than a few feet. It will not penetrate the soil more than a few inches before solidifying. Asphalt cement does not mix with or become soluble in water.
Yes. Current testing done by the air quality regulators indicates that there are no risks to citizens living near plants that follow air quality regulations. In 2002, the United States Environmental Protection Agency acknowledged in two separate actions that asphalt facilities are not a major source of hazardous air pollutants. We are proud that all of our plants conform to strict regulations set by the EPA, EGLE, and cities where our plants are located. Elmer’s has also received the Diamond Achievement Award in our industry for promoting and maintaining a clean and environmentally conscious plant facility. Continuous measures are taken to improve air quality such as longer air stacks, odor masking agents for the natural asphalt, and dust and emissions control procedures.
Hot mix asphalt has to be placed and compacted while it is hot - in excess of 250 degrees F. The farther you have to carry it, the cooler it gets. If it gets too cool, it is no longer acceptable for paving. So asphalt facilities must be located close to work sites.