Investigation of Blending Mechanisms for Reclaimed Asphalt Pavement Binder and Virgin Binder in Laboratory-Produced Reclaimed Asphalt Pavement Mixtures

The use of reclaimed asphalt pavement (RAP) in new pavement construction or pavement rehabilitation projects contributes to sustainable construction. However, the blending between RAP binder and virgin binder could significantly affect pavement performance, especially in regard to cracking. Currently, studies to understand the different blending stages between RAP binder and virgin binder in a RAP mix and the effects of each blending stage on mix performance are lacking. In this study, three blending stages were investigated: Stage 1: RAP binder transfer to virgin aggregate, Stage 2: mechanical blending, and Stage 3: diffusion. The objectives of this study are to propose a laboratory mixing scheme to distinguish the effects of each of the three stages for blending between RAP binder and virgin binder; investigate the effects of each blending stage on the rheological and fracture performance properties of the study mixes; and identify the primary mechanisms of blending between RAP binder and virgin binder in laboratory-produced RAP mixtures. Tests, including dynamic modulus and creep compliance in indirect tensile (IDT) mode and IDT fracture tests at 20 degrees C and -10 degrees C, were conducted to determine the rheological and fracture properties of mixtures. Results indicated that at RAP binder replacement ratio of 26%, Stage 3 diffusion is the most dominant in affecting the rheological and fracture properties of RAP mixes compared with Stage 1 RAP binder transfer and Stage 2 mechanical blending.