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

摘要

The use of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphaltrn(HMA) has become a widely accepted practice by most of the paving industry.rnAs the cost of virgin materials continues to rise, the use of cost efficient andrnquality recycled materials is also increasing, and Reclaimed Asphalt Shinglesrn(RAS) have begun to be considered a viable source of recycled binder andrnaggregate. This study compares the laboratory performance of four HMArnmixes: one that contains only RAP, and three mixes that contain different RASrnproducts. Superpave mixture designs resulted in higher asphalt contents andrnVMA values for the RAS mixtures as compared to the RAP mixture. Testingrnincluded the determination of PG grade, shear modulus and phase angle, creeprnstiffness and slope values, and critical cracking temperatures for binderrnrecovered from the HMA mixtures. Mixture testing included complexrnmodulus and Thermal Stress Restrained Specimen Tensile Strength tests on allrnfour mixtures and fatigue testing on two mixtures. The Hirsch model was usedrnto backcalculate the binder shear modulus; values for binder modulus andrnphase angle were used to determine the effective high temperature PG grade ofrnthe mixtures. The binder testing indicates that the RAS mixtures are stifferrnthan the RAP mix at high temperatures and would perform better with respectrnto low temperature cracking. The mixture testing shows that the RAP mix isrnstiffer and has a poorer fatigue resistance at intermediate temperatures than thernRAS mixtures, while all four mixtures have similar low temperaturernperformance.