Effect of Recycled Asphalt Pavement Binder on Rheology of Crumb Rubber–Modified Binder—An Experimental, Analytical, and Analogical Study

The popularity of recycled asphalt pavement (RAP) is on the rise because of the benefits of sustainability. In an unavoidable scenario wherein crumb rubber–modified binder (CRMB) is adopted as a base binder in RAP mixes, the binder from RAP will blend with CRMB, thereby influencing its rheology and performance at high, intermediate, and low temperature. Hence, in this study, binder extracted from two RAP sources (RAP X and RAP Y) was blended with CRMB at varying proportions of 15, 25, and 40 % by weight. Isochronal temperature sweeps, isothermal frequency sweeps, and bending beam rheometer tests were conducted on the prepared blends. Thereafter, analytical and analogical studies were performed using master curve construction, 2S2P1D, and Huet modelling. The results indicated that RAP from different sources affects the high-, intermediate-, and low-temperature performance of CRMB. Different RAPs were observed to have contrasting effects on high-temperature performance grading. Intermediate-temperature performance based on cross-over temperature (TCROSS-OVER) indicated a compromise because of the inclusion of RAPs. An evaluation of the differences among critical temperatures at low temperature (ΔTc) indicated the degradation of low-temperature performance. Such changes in high-, intermediate-, and low-temperature performances were validated by complex modulus (G*), stiffness (S(t)), and stress relaxation (E(t)) master curves. Finally, the 2S2P1D and Huet model were observed to depict reasonably good fits for the prepared blends. This study concludes that RAPs from different sources have contrasting impact on CRMB and may adversely impact the intermediate- and low-temperature performance.