Effects of ageing and recycling agents on the multiscale properties of binders with high RAP contents

Abstract

ABSTRACT The use of reclaimed asphalt pavement (RAP) in road construction has become a common practice in the asphalt industry due to environmental and economic benefits. However, since RAP is an aged material, recycling agents are typically used to reduce the stiffness of the recycled asphalt mixture and make it less prone to cracking at high RAP contents. This study evaluates the effect of ageing and the use of recycling agents on the rheological, microstructural, and micromechanical properties of binder blends with high RAP contents. A total of 27 binder blends were prepared with different recycled binder ratios (0.22, 0.31 and 0.5), recycling agent doses (0%, 1.2%, 5.5% and 9%), virgin binder performance grades (PG 58-28 and PG 52-34) and ageing conditions. The microscopic properties of the binder blends were characterised using atomic force microscopy (AFM). AFM results provided an evaluation of the microstructural homogeneity of the blends, with a good correlation with the binder blends macroscopic rheological properties. The addition of recycling agents improved the homogeneity of the binder blends by reducing the variation in modulus among the different phases in the microstructure. AFM proved to be a useful tool to evaluate rejuvenated binder blends at the microscale level.