Investigation of the aging behaviors of reclaimed asphalt

Reclaimed asphalt pavement (RAP) has been extensively used in asphalt pavement nowadays. Under the coupled impacts of traffic loading and environmental factors, aged binder in RAP would suffer the secondary aging, and seriously affect the performance of the reclaimed asphalt binder. This study explored the aging behaviors of the composite asphalt binder (50% RAP binder + 50% SBS binder). Comparison was made in aging performance between RAP binder, virgin SBS binder and their composite by conducting RTFOT test with different aging durations. Centrifugal extraction and rotary evaporator methods were firstly adopted to recover RAP binder. Rheology tests, including the DSR temperature sweep test, multiple stress creep recovery (MSCR) test and linear amplitude sweep (LAS) test, were conducted. Results showed that the high temperature stability of composite binder increased significantly after the secondary aging. With increasing the aging duration, the stiffness of the composite binder increased, which led to the decrease of creep deformation and deformation recovery. The effect of RAP binder on the creep characteristics of composite binder was greater than that of the SBS binder, and the variations of R, Jnr, R-diff and Jnr-diff of the composite binder with the aging duration remained basically the same as that of the RAP binder. The fatigue resistance of binders decreased gradually with the increasing the aging duration. For a given level of aging duration and strain, the fatigue life Nf of the composite binder always lay between the RAP binder and the SBS binder. The fatigue life attenuation law of composite binder is almost the same as that of RAP binder in the short-term aging stage (less than 85 min), while for long-term aging the fatigue life attenuation law is more similar to that of SBS binder.