Influence of mobilized RAP content on the effective binder quality and performance of 100% hot in-place recycled asphalt mixtures

Abstract

Hot in-place recycling (HIR) is a promising technique to consume 100% recycled asphalt pavement (RAP) for pavement surface rehabilitation. When RAP aggregates are incorporated in asphalt mixtures, a proportion of the RAP binder can be mobilized by the virgin binder or additive and achieve a homogenous binder blend, named “the effective binder blend.” There exist two major concerns of using 100% RAP in HIR mixes: 1. How much of the RAP binder can be mobilized to coat aggregates? 2. What are the contributions of the mobilized RAP binder to the performance of HIR mixes? This study firstly developed an approach to quantify the mobilized RAP content in HIR mixes. Afterward, the effective binder blends were prepared in the laboratory, based on the mobilized RAP and virgin asphalt percentage. Finally, the dynamic shear rheometer test and sessile drop method were adopted to characterize the effective binder qualities, while AMPT and Ideal-CT tests were utilized for mixture performance evaluation. Results showed that the mobilized RAP binder altered the binder qualities of the effective binder blends and also the effective asphalt content in HIR mixes. The binder qualities, including rheological properties and surface free energy, contributed to the different stiffness and cohesion of the effective binder blends in HIR mixes. However, the effective asphalt content proved to dominate the cracking resistance of HIR mixes.