Using Reclaimed Asphalt Pavement in Pavement-Preservation Treatments

Using reclaimed asphalt pavement (RAP) has grown significantly since the oil embargo of the 1970s. The National Asphalt Pavement Association reported that over 71 million tons of RAP were used in 2014 (NAPA 2015). RAP was traditionally used in warm-mix asphalt (WMA) and hot-mix asphalt (HMA) construction, including conventional and thin HMA overlays, but there is growing interest in using RAP in non-HMA projects, such as chip sealing and microsurfacing. Limits on the use of RAP in non-HMA pavement-preservation treatments are not as well known since there is limited research on how RAP affects the performance of such treatments. The purpose of this study was to investigate the performance of RAP in non-HMA pavement-preservation treatments to determine if performance trends similar to those found in WMA and HMA construction projects are evident. This study also documented current practices for using RAP in non-HMA pavement-preservation treatments, including guidance on design criteria, material specifications, construction techniques, costs, inspections, and performance data. Multiple agencies have used RAP in chip seals for a variety of reasons, including cost savings and environmental sustainability goals. One agency specified exclusively using reclaimed asphalt pavement aggregate in slurry seals (RAP slurry) sealing and microsurfacing, allowing full replacement of virgin aggregate. The performance characteristics of pavement preservation treatments using RAP or virgin aggregate are similar, as are chip seal application rates and construction techniques. RAP slurry seals are reported to benefit from pneumatic tire roller passes that seat the RAP particles and seal the treatment surface texture. During this study, several agencies reported either experimenting with or adopting RAP materials in pavement preservation projects, suggesting continued use of RAP in pavement-preservation projects will continue.  This report can be downloaded from the FHWA web site at https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/21007/index.cfm