Novel concentration master curve and rheological characterization of recycled asphalt binders

The recycling of asphalt pavements requires a good understanding of the material's characteristics. However, the rheological behavior of recycled binder is still not well understood. In this study, a novel method is introduced to construct the master curve of the recycled binders. The concentration of reclaimed asphalt pavement (RAP) binder is used to find the shift factors of the master curve. This master curve is called the concentration master curve (CMC). To verify the applicability of the concept, the CMC was plotted for three different RAP sources procured from two states and the capital of India. The percentage of RAP binder content in the recycled binders was varied (0, 15, 25, 40, 65, 80, and 100%) by weight of the total binder. In all three cases, smooth master curves were obtained. To calculate the allowable RAP, an alternative approach based on the damping energy area (DEA) of recycled binders was proposed. It was found that the allowable RAP content based on the DEA criteria was 40-50% less compared to the conventional high PG temperature (PGH) criterion. An attempt is made to understand the rheological interaction between the RAP binder and RA using the recycled binder compatibility index (RBCI). It was observed that the RAP source is the determining factor behind the compatibility and interaction level between the RAP binder and RA in a recycled binder.