Evaluation of the improved properties of SBR/weathered coal modified bitumen containing carbon black

One problem of polymer modified bitumens (PMBs) is the poor compatibility between polymer and bitumens. In this paper, the improved properties of bitumen binders containing various kinds of additive including styrene butadiene rubber (SBR), weathered coal (WC) and carbon black (CB) under different concentrations are investigated. To assess the effects of the type and concentration of the additive on classical properties of bitumen binders, the softening points, penetration, penetration index (PI), ductility and Fraass breaking points before and after RTFOT aging are tested. The dynamic mechanical analysis (DMA) of these binders before and after ageing had been characterized by dynamic shear rheometer (DSR) using a combination of temperature and frequency sweeps. With higher polymer concentrations, it produced a highly elastic network which increases the viscosity, complex modulus and elastic response of the PMBs, particularly at high service temperatures. However, ageing of PMBs tended to result in a decrease in the elastic response of the modified bitumens. It also has been confirmed that the morphology observed by optical microscopy and scanning electron microscope (SEM) revealed the compatibility among SBR, WC and bitumen. The storage stability of binder was also improved significantly.