RAP or RAS? The Differences in Performance of HMA Containing Reclaimed Asphalt Pavement and Reclaimed Asphalt Shingles

The use of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphalt (HMA) has become a widely accepted practice by most of the paving industry. As the cost of virgin materials continues to rise, the use of cost efficient and quality recycled materials is also increasing, and Reclaimed Asphalt Shingles (RAS) have begun to be considered a viable source of recycled binder and aggregate. This study compares the laboratory performance of four HMA mixes: one that contains only RAP, and three mixes that contain different RAS products. Superpave mixture designs resulted in higher asphalt contents and VMA values for the RAS mixtures as compared to the RAP mixture. Testing included the determination of PG grade, shear modulus and phase angle, creep stiffness and slope values, and critical cracking temperatures for binder recovered from the HMA mixtures. Mixture testing included complex modulus and Thermal Stress Restrained Specimen Tensile Strength tests on all four mixtures and fatigue testing on two mixtures. The Hirsch model was used to backcalculate the binder shear modulus; values for binder modulus and phase angle were used to determine the effective high temperature PG grade of the mixtures. The binder testing indicates that the RAS mixtures are stiffer than the RAP mix at high temperatures and would perform better with respect to low temperature cracking. The mixture testing shows that the RAP mix is stiffer and has a poorer fatigue resistance at intermediate temperatures than the RAS mixtures, while all four mixtures have similar low temperature performance.