Priti Rai, Praveen Kumar, Nikhil Saboo
The use of rejuvenating agents (RAs) is crucial in restoring the properties of aged asphalt binder during hot mix recycling. Studies on the effectiveness of RAs for unmodified binder (UMB) and polymer-modified binder (PMB) under different aging severities are scarce, yet necessary for enabling repeated hot mix recycling. This study examined the rejuvenation capacity of four RAs (fresh mustard oil, waste cooking oil, waste engine oil and tall oil) for UMB and PMB. Laboratory aging was performed to achieve aging index (AI) of 1.27 ± 0.01 and 1.5 ± 0.01, representing moderate and severe aging degrees. Various RA dosages were added to the aged binder, and the physical, rheological and performance properties were measured to estimate the optimum rejuvenator dosages. A storage stability test and Fourier transform infrared (FTIR) spectroscopy were performed to evaluate RA compatibility and chemical changes induced by the RAs, respectively. The results showed that RAs effective for UMB were not equally effective for PMB because of polymer degradation in aged-PMB. RA performance was highly dependent on binder type and aging severity. High RA dosages, especially in severely aged binders, can lead to poor storage stability. RAs restoring stiffness (G*) and phase angle (δ) are recommended for efficient hot mix recycling.