Reclaimed asphalt pavement (RAP) continues to be the most recycled product in America. A 2018 US survey conducted by the National Asphalt Pavement Association (NAPA) shows that 82.2 million tons of RAP was reused in new hot mix asphalt (HMA) pavements; this equated to an average RAP content of 21 % which is similar to estimates in Canada where about 15-20 % of the RAP is reused. The same survey highlighted that at the end of 2018 approximately 110 million tons of RAP was stockpiled, this continues to be problematic from a sustainability point of view in both the US and Canada for many reasons. RAP has been successfully utilized in HMA since the 70’s. Over the years properly engineered or designed asphalt mixtures incorporating RAP have been shown to perform as good as standard HMA. Rejuvenating agents such as organic compounds (e.g. aromatic oils) generated from petroleum processing have also been utilized to achieve the desired quality. Research continues and the ongoing evaluation of newer recycling agents, (for instance waste or vegetable oil derivatives) has merit for several good reasons. This paper looks at the use (past and present) and performance of these products and provides a perspective into future use. Essentially, we want to better understand how to engineer and produce mixtures containing various RAP contents (and in some jurisdictions incorporating Reclaimed Asphalt Shingles – RAS). In general, the focus of this paper is on how to improve cracking performance; the development of a potential framework for the use of rejuvenating agents is presented along with a discussion on the proper design and production of durable quality mixtures using RAP.
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