Influence of chemical characteristics of RAP binders on the mechanical properties of binders and mixes

Abstract

Utilization of reclaimed asphalt pavement (RAP) materials in the asphalt layer construction has emerged as an important rehab ilitation option for asphalt pavements. The properties of reclaimed asphalt material will be different from those of the initial (virgin) asphalt mixture due to the aging of the binder. Resilient modulus is an important material parameter used for the design of pavements. The mechanical behaviour of the mix and the binder is expected to be influenced by the chemical composition of the binder. In this study, the effect of the chemical composition of virgin and reclaimed asphalt pavement (RAP) binders on the resilient modulus (Mr) of RAP mixes has been evaluated. This is done by testing different RAP mixes prepared using bitumen samples containing different proportions of RAP binder. The RAP mixes prepared using one aggregate gradation (mid-point gradation recommended by the Ministry of Road Transport and Highways for Bituminous Concrete -1) and different RAP contents (0, 15, 25, 35 and 45%) with VG-30 as virgin binder, were tested for their resilient modulus values at different temperatures (15, 25 and 35°C) and frequencies (0.5, 1, 1.5 and 2 Hz). The chemical composition of the binder blends was evaluated with the help of Fourier transform infrared spectroscopy (FTIR). The relationship between the chemical indices and the rheological parameters has been examined. Ketones, aliphatics and aromatics are found to have good correlation with rheological properties. The chemical indices also are found to have good correlation with the resilient moduli of the mixes.