To establish a baseline price for asphalt, 2013 average Department of Transportation price bids for HMAC were collected from California, Oregon, and Washington, which were used to calculate an average. A variety of sources indicate the cost savings for a 30% RAP mix compared to using virgin materials are between $6 and $10 per ton. For this study we used average of $8 per ton. The majority of this cost savings comes from replacing the virgin asphalt binder, which is the most expensive component of asphalt. It’s important to note that the costs used for this analysis represent “first costs” only and do not include costs associated with maintenance or adjustments for differences in the expected lifespan of the material. Lifecycle costs should be considered in a future version of this document.
One of the great benefits of RAP is that it’s a tried and true technique and has been widely used since the 1970, so there is already an understanding of its use in asphalt mixtures. In fact, asphalt pavement is recycled at a rate of over 99 percent, making it the most recycled material in the U.S. . The reuse of asphalt reduces the amount of required aggregate and virgin binder, thus reducing energy costs and GHG emissions. RAP can be used in any asphalt mix and can typically represents between 10 - 30% of any asphalt mixture. Another benefit of RAP is that because of its increased stiffness, it can help to prevent deformations in asphalt such as rutting.
However, there are some concerns that can impact the operations of using RAP. There is a great variability among RAP stockpiles, stockpiles properties should be considered on an individual basis in developing a mix design. Some of the stockpile variability is due to oxidization of the RAP by sunlight and the atmosphere while it was asphalt, resulting in RAP material that can be a very stiff and difficult material to work with. This can also increase the possibility of fractures and cracking as the RAP asphalt becomes brittle. This is a particular problem in areas that experience low temperatures, but is dependent on the quality of the RAP.
Selecting the appropriate mix design is critical to the use of asphalt concrete materials. Staff involved in the purchasing materials or bidding projects that include these materials, should select the mix design properties needed for the environmental conditions, traffic loading and available materials. Quality control testing to ensure longevity of the project is important.
RAP is generally available, though it is dependent on several factors, such as how much RAP is generated in the area. A majority of asphalt plants have the necessary machinery to capitalize on this resource and if a street is being repaved, municipalities can reclaim the asphalt pavement of the old street and use it in the repaving process.