Evaluation of silicone resin enhanced recycled concrete aggregates for asphalt mixture application

The utilization of recycled concrete aggregate (RCA) in asphalt mixtures represents a sustainable solution to both natural aggregates conservation and construction waste reduction. However, the rough and porous surfaces with weakly-bonded residual mortar of RCA lead to poor adhesion with asphalt, which poses significant challenges to its effective application. This study aims to evaluate silicone resin (SR) enhanced adhesion at the RCA/asphalt interface and clarify the reaction kinetics. The road performance of the modified asphalt mixture was evaluated through Marshall stability test, rutting test, and low temperature bending test. The improvement in adhesion due to silicone resin was assessed using boiling water test and pull-off test. Surface morphology, chemical bonds, and functional group variations of RCA were characterized before and after modification, and molecular dynamics (MD) simulations were employed to elucidate the modification mechanism. The results demonstrated that silicone resin significantly enhanced the Marshall stability and low-temperature crack resistance of the asphalt mixture. Meanwhile silicone resin effectively improved the adhesion performance and bond strength between asphalt and RCA. The optimal dosage of silicone resin was determined to be 3 % of the RCA mass. During the modification process, silicone resin effectively filled microcracks and pores on RCA surfaces and introduced new chemical bonds (C-O and C-C). The simulation results further indicate that silicone resin promotes the diffusion of asphalt on aggregate surfaces, while forming interactions such as ionic bonds and hydrogen bonds with both RCA and asphalt, thereby enhancing the interfacial adhesion. In addition, the use of silicone resin to modify RCA is environmentally and economically feasible compared to conventional aggregates.