While the research and development of the SUPERPAVE asphalt mixture design and analysis system did address the use of polymer modified asphalt binders in the specification of material performance properties, no recommendations or procedural guidelines were given for the use of recycled materials. The use of recycled asphalt pavements (RAP) in new paving mixtures is not an innovative idea. RAP has been called one of the most recycled materials in the world, and its use in paving mixtures has been shown to have environmental, economic and performance benefits. In this study, four different RAP stockpiles were sampled and the characteristics of each RAP material were investigated in terms of binder content, aggregate gradation and the rheologic characteristics of the reclaimed RAP binder. The reclaimed RAP binders were blended with several different virgin performance graded binders in order to determine how RAP binder concentration affected the stiffness and performance grade of the RAP -- virgin binder blends. Recommendations were made on how to select virgin binder grade andor RAP concentration combinations to fulfill a project's binder grading requirements. The effects of RAP were also investigated in terms mixture design, and recommendations were made with regards to material handling and specimen fabrication procedures. Asphalt concrete mixtures containing RAP were characterized in terms of stiffness and resistance to plastic strain using SUPERPAVE testing methods, and the results of these tests were compared to those of virgin material mixtures. Assuming a simulated pavement cross section and traffic loading, the results of this performance testing were used in performance prediction models to estimate how pavements constructed with RAP would perform compared to those made from 100% virgin materials. The predicted performance of pavements containing up to 40% RAP (by weight) was found to be similar or slightly better than that of virgin material pavements.

Keywords: RAP, asphalt concrete, pavements recycling.

TRB's National Cooperative Highway Research Program (NCHRP) Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content describes proposed revisions to the American Association of State Highway and Transportation Officials (AASHTO) R 35, Superpave Volumetric Design for Hot Mix Asphalt, and AASHTO M 323, Superpave Volumetric Mix Design, to accommodate the design of asphalt mixtures with high reclaimed asphalt pavement contents.

The use of reclaimed asphalt pavement (RAP) in new asphalt mixes replaces a portion of the virgin aggregate and binder, which will help with cost saving in pavement construction as well provide several environmental benefits. Currently, the Federal Aviation Administration (FAA) has no requirements and specifications for the use of RAP in accordance to the FAA Specification P401 and this research will help with the development of such specifications. The objective of this study is to create Superpave mix designs for airfields using RAP and subject them to performance related testing to provide information regarding any issues with the mix design procedure. Another objective of this project is to perform and interpret the results of laboratory testing with regard to the behavior/performance of asphalt mixes containing RAP and evaluate their suitability for use in airport pavements The experimental plan in this study included 10 different hot mix asphalt (HMA) mixes made with three different binder grades (PG 64-22, PG58-28, PG76-22PM), three RAP sources (New York, California, Alabama), and two RAP percentages (25%, 40%). A control mix with no RAP was also tested for comparison. The results of this study will be used to develop mix designs for accelerated pavement testing at the FAA National Aviation Pavement Test Facility (NAPTF) in Atlantic City, New Jersey. The results indicate that meeting the FAA's voids in mineral aggregate (VMA) requirement was problematic and while developing the mix designs with RAP the total binder content had to be reduced in order to meet the current FAA air void and VMA requirements. Performance testing showed that incorporation of RAP will improve the performance properties when compared to their respective control mixes. The statistical analysis showed that percent of RAP (by binder replacement rate) is the most significant factor affecting all performance testing and that binder grade is the least significant factor on all performance testing. It is recommended that results from this study be validated with more performance testing, including additional testing with different binder grades and performance testing for low temperature cracking. There also needs to be more testing on mix designs for airfield pavement with the addition of RAP to develop voids filled with asphalt (VFA) and dust proportion (DP) specifications.

"This synthesis will be of special interest and usefulness to design engineers, materials technologists, and others seeking information on the potential use of recycled materials in design, construction, rehabilitation, and maintenance of pavements, bases, and other components of the highway system. Detailed information is presented on procedures for pavement recycling."--Avant-propos.