Effect of Reclaimed Asphalt and Virgin Binder on Rheological Properties of Binder Blends

With the introduction of the Superpave mix design, many questions were raised about the proper method of incorporating Reclaimed Asphalt Pavement (RAP) in Superpave. During service, the blend of aggregates and binders undergoes various physical and rheological changes that have to be considered in the design process to ensure that HMA mixtures with RAP will perform very well. The issue of the resulting blended binder stiffness is very important for designing mixes. The binder that is recovered from the RAP is stiffer than virgin binder due to the aging that has occurred during its service life. Because of this, the blended RAP-virgin binder will increase in stiffness. The objective of this paper is to investigate the rheology of RAP-virgin binder blends. Three virgin binder grades, a PG 52-28, PG58-28 and PG64-22 were blended with two different RAP binder concentrations, 20% and 40% by total binder mass. The results of the Dynamic Shear rheometer (DSR) testing of the unaged, Rolling Thin Film Oven (RTFO) and Pressure Aged Vessel (PAV) aged binder blends showed similar trends in that as the concentration of RAP binder increased from 20 to 40 percent, the stiffness of the blend increased 150 to 200 percent for the blends containing PG52-28 and PG58-28 virgin asphalts. Results also shows that virgin asphalt grade used in a particular blend seemed to have an effect on the stiffness increase of the resulting asphalt blends as the RAP binder concentration increased.