USE OF RECLAIMED ASPHALT PAVEMENT (RAP) UNDER SUPERPAVE SPECIFICATIONS: A REGIONAL POOLED FUND STUDY

This regional pooled fund project was conducted to investigate the performance of Superpave asphalt mixtures incorporating Reclaimed Asphalt Pavement (RAP). This study was closely coordinated with a national study on the same topic [National Cooperative Highway Research Program (NCHRP) 9-12, Incorporation of Reclaimed Asphalt Pavement in the Superpave System]. Specifically, this regional project looked at typical materials from the North Central United States to determine if the findings of NCHRP 9-12 were valid for Midwestern materials and to expand the NCHRP findings to include higher RAP contents. Three RAP materials from Indiana, Michigan and Missouri were evaluated. Mixtures were designed and tested in the laboratory with each RAP, virgin binder and virgin aggregate at RAP contents up to 50%. The laboratory mixtures were compared to plant produced mixtures with the same materials at the medium RAP content of 15-25%. Binder and mixture tests were performed. Briefly, the results showed that mixtures with up to 50% RAP could be designed under Superpave, provided the RAP gradation and aggregate quality were sufficient. In some cases, the RAP aggregates limited the amount of RAP that could be included in a new mix design to meet the Superpave volumetric and compaction requirements. Linear binder blending charts were found to be appropriate in most cases. In general, increasing the RAP content of a mixture increased its stiffness and decreased its shear strain, indicating increased resistance to rutting. It is important to consider the RAP aggregate gradation and quality in the mix design, since a poor aggregate structure could reduce mixture stiffness and ultimately performance. Provided the RAP properties are properly accounted for in the material selection and mix design process, Superpave mixtures with RAP can perform very well.