Effects of Physical Hardening on Low-Temperature Properties of Asphalt Binders Containing Reclaimed Asphalt Pavement

Reclaimed asphalt pavement (RAP) materials are widely used in sustainable construction of the asphalt pavement, which has evident advantages in solving the problem of material costs and waste disposals. However, there are few studies on the influence of RAP materials on the physical hardening of asphalt binders. In this paper, the physical hardening rate from the dynamic mechanical analysis test and grade loss deduced by the extended bending beam rheometer experiment were used to characterize the physical hardening of the RAP-modified asphalt binder at low temperatures. The results show that the loading time-conditioning time superposition principle is suitable to determine the physical hardening rate of RAP-modified asphalt binder through a smooth master curve and verification of the typical 2S2P1D rheological model, and grade loss can be predicted by the physical hardening rate using their good correlation. The RAP binders can accelerate the degree of physical hardening and increase the thermal stresses of the asphalt binder, and these effects are more evident for the RAP binder with longer aging time and higher content. The base asphalt with less wax content will act as a regenerant, which can accommodate more content of the RAP materials to produce a new usable asphalt binder.