Reclaimed Asphalt Pavement in Asphalt Mixtures: State of the Practice
Over 90 percent of highways and roads are constructed with hot mix asphalt (HMA). As the U.S. infrastructure ages, these highways and roads must be maintained and rehabilitated. According to the Federal Highway Administration's (FHWA) recycled materials policy: The same materials used to build the original highway system can be re-used to repair, reconstruct, and maintain them. Where appropriate, recycling of aggregates and other highway construction materials makes sound economic, environmental, and engineering sense.
With increased demand and limited aggregate and binder supply, HMA producers have begun using reclaimed asphalt pavement (RAP) as a valuable component in HMA. As a result, there has been renewed interest in increasing the amount of RAP used in HMA.
While several factors influence the use of RAP in asphalt pavement, the two primary factors are economic savings and environmental benefits. RAP is a useful alternative to virgin materials because it reduces the use of virgin aggregate and the amount of virgin asphalt binder required in the production of HMA. The use of RAP also conserves energy, lowers transportation costs required to obtain quality virgin aggregate, and preserves resources. Additionally, using RAP decreases the amount of construction debris placed into landfills and does not deplete nonrenewable natural resources such as virgin aggregate and asphalt binder. Ultimately, recycling asphalt creates a cycle that optimizes the use of natural resources and sustains the asphalt pavement industry.
In order for it to be successful, recycled asphalt pavement must be cost-effective, perform well, and be environmentally sound. To ensure that these requirements are met, FHWA promotes the following:
• The use of recycled material in the construction of highways to the maximum economical and practical extent possible with equal or improved performance.
• The use of RAP in HMA because RAP can have a large economic, environmental, and engineering impact in pavement recycling.
The use of RAP may grow by increasing the number of highway construction and rehabilitation projects that use RAP, as well as by increasing the amount of RAP used in specific projects. To meet these goals, the following tasks were identified:
• Establish a public and industry working group.
• Create funded and coordinated research and demonstrations projects.
• Research deployment and technology transfer for information dissemination and education.