Utilization of Reclaimed Asphalt Pavement in the United States
Professor Serji Amirkhanian, Ph.D., Professor of Civil Construction and environmental Engineering, University of Alabama, Tuscaloosa, Alabama, USA
Adj Prof of Civil Engineering, IIT Madras
Adj Prof of Civil Engineering, IIT Madras
Introduction
Recycling of asphalt pavements started around 1915 in the United States, but it did not become a common practice until later (1970s) when asphalt binder prices skyrocketed as a result of the Arab oil embargo. The 1970s marked the beginning of the widespread use of reclaimed asphalt pavement (RAP) in asphalt pavements in the United States. In addition, in the 1980s, some field trials with high RAP contents were constructed and evaluated. However, in early years, many state Department of Transportations (DOTs) used only a low percentage of RAP materials in their hot mix asphalt (HMA) mixtures. One major reason for this was that the mixtures containing high RAP contents could result in increased "blue smoke" emissions from plants since the RAP materials were fed directly into the path of hot gasses. It is important to note that with the modern design of new plants, this is no longer a major concern. Also, based on many years of field experience, the industry has developed very effective techniques to introduce the proper proportion of RAP into the HMA mixtures.Over 90% of U.S. highways and roads are constructed with hot mix asphalt (HMA) and as this infrastructure ages, these highways and roads must be maintained and rehabilitated. The Federal Highway Administration's (FHWA) recycled materials policy states that:
"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."
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NBM&CW September 2015
