There are many reasons why asphalt pavement has become the preferred choice of road pavement material. Most roads are constructed in layers, with each layer playing a part in delivering the best infrastructure possible. When asphalt pavement is used it brings numerous benefits that all can enjoy.
Asphalt pavements are perpetual and have the ability to last forever when designed properly. Routine maintenance is essential for anything that is used on a regular basis. Our roads are no exception. By choosing asphalt, the maintenance can be done quickly with minimal traffic disruption. Using asphalt on our roads can significantly improve the ride quality and fuel consumption of vehicles traveling these roads and contribute to the longevity of the road.
Asphalt pavement provides a smoother surface. A smooth surface reduces damage to the pavement, necessitating fewer repairs. It improves fuel efficiency and reduces wear and tear on vehicles, making the choice for asphalt a great economical decision. Finally, paving roads and highways with asphalt significantly reduces the noise generated by the tire/pavement interface providing for a quieter ride experience for the motorist.
Paving with asphalt cuts construction project time significantly. As a result, traffic flows more smoothly and impact on commerce is minimized. Asphalt paving projects can be planned and carried out to take advantage of off-peak periods, like nights and weekends. Asphalt is ready for traffic right after it is compacted and cooled, which means better traffic flow, minimized closures and happier motorists.
Asphalt is a low-cost building material. It is less expensive, not just in actual cost, but also in terms of the time it takes to complete construction projects. It is adaptable in that asphalt is a reliable weather resistance material and can be designed for low and high traffic conditions. It can withstand the harshest of weather and the heaviest of semi-trailers. Asphalt can be designed to fit a specific purpose.
Asphalt’s safety feature is related to its smooth-like finish. It offers drivers skid resistance and reduces splash back while providing better visual distinction between road markings. Asphalt also helps keep roads free from ice and snow.
Asphalt is a recycled material, it can be used over and over, and its life cycle never ends. Asphalt roads can be dug up and then re-used again. This makes asphalt a wise choice when choosing road material. When we use it we are preserving our natural resources by reusing the same material over again.
Q: What materials are used to produce asphalt pavement?
A: Hot mix asphalt can be simplified into two major components: liquid asphalt cement and aggregates. The liquid asphalt cement (often called asphalt binder) is material that coats the aggregate particles and acts as the glue that holds the mix together. The aggregates may consist of natural aggregate (river gravel and sands) or processed aggregates (from quarry and blasting operations). The aggregates provide the structure and framework that gives an asphalt mixture its stability and strength. Another vital component to a well constructed asphalt pavement is the presence of air voids in the mixture. The amount of air voids in the asphalt is controlled through the aggregate gradation and the quantity of liquid asphalt. The proper blend of asphalt and aggregates is determined prior to construction (during the mix design phase) in order for the mixture to have the desired properties.
Q: Are all asphalt mixtures the same?
A: No, it is a common misconception that asphalt is asphalt and that the asphalt used on the interstate roadways is the same asphalt used in residential driveways. An asphalt mixture that is designed for use on a heavily traveled highway has very different characteristics than those used in low volume residential applications. Those differences may include different aggregate types, sizes and proportions as well as different grades of liquid asphalt. Feel free to contact the APAO office or your local APAO producer member to assist you in determining which mix is appropriate for your application.
Q: What is Perpetual Pavement?
A: Perpetual pavement is the name coined to describe a three-layer, flexible pavement design and construction concept. Application of the concept produces a deep-strength asphalt pavement that can resist structural fatigue distress indefinitely (more than 50 years) and, thus, results in a long-lived pavement. These long-lasting structural bases can be economically maintained by replacing just the surface, never needing total removal and replacement. For more information on perpetual pavements, see the concept paper prepared by the Asphalt Pavement Alliance.
Q: What is this Superpave I keep hearing about?
A: Superpave is a system of material specifications and laboratory mix design methods based on performance criteria developed under the Strategic Highway Research Program (SHRP). Using the Superpave system, materials and mixes can be designed to reliably perform under any loading or environmental conditions. The Superpave system is undergoing continuing development nationally. The Oregon DOT is fully implementing Superpave in 2002 on all state projects. In general, Superpave designed asphalt mixtures rely more on stone-to-stone contact, they are generally more durable and last longer.
Q: What product is recycled the most in the United States?
A: Americans who recycle their aluminum cans, newspapers, plastics and glass are helping to preserve our nation's resources. But daily and quietly, the hot mix asphalt industry is recycling asphalt pavement to a substantially larger extent.
Asphalt pavement is unquestionably the nation's most widely recycled product.
The Federal Highway Administration reports that 73 million metric tons of the 91 million metric tons (or 80.3 million of the 100.1 million tons) of asphalt pavement that is removed each year during resurfacing and widening projects is reused as part of new roads, roadbeds, shoulders and embankments. That's a recycling rate of 80 percent.
In terms of tonnage, only scrap metal comes close at 70 million tons, which represents a recycling rate of 64 percent for steel.
A possible misconception is the extent to which the recycling of consumer goods occurs. The EPA says Americans recycle only 28 percent of the materials in the municipal solid waste stream. The EPA says that of the 217 million tons of solid waste generated in 1997, the latest year for which figures are available, we recycled 60.7 million tons of paper and paperboard, yard trimmings, glass, metal, plastic and other materials.
Thus, the 80.3 million-ton volume of recycled asphalt pavement is approximately one-third higher than the total volume of 60.7 million tons of post-consumer recycling. And it's double the volume of paper, glass, plastic and aluminum combined.
Q: What impact does the production and use of HMA have on the environment?
A: In many respects, hot mix asphalt (HMA) is the environmentally-friendly paving material. First, HMA materials are 100 percent recyclable. Virtually all of the reclaimed asphalt pavement (RAP) that is removed from existing streets and highways is recycled into new HMA. Because this recycling of HMA is economical, it occurs without the need for government mandates or subsidies. HMA also has been shown to consume less energy than other materials and systems. A study done by the Asphalt Institute indicated that a comparably-designed HMA pavement required only about half the total energy to construct as a comparable Portland cement concrete pavement.
Improvements in technology have been steadily reducing the airborne emissions from the production and placement of HMA. Dust from the drying of aggregates is the major emission and is now almost totally captured and recycled. Other emissions are primarily combustion products from the burning of fuel to heat the aggregates and fumes from hot asphalt itself. Fuel burners are now much more efficient, resulting in very complete combustion. Studies to date by the government and industry have shown emissions levels to be very low and have not identified any health hazard associated with exposure to asphalt fumes. Nevertheless, the industry continues to develop improved technology for reducing emissions and minimizing exposure.