Development of a new rejuvenator for aged SBS modified asphalt binder

The objective of this study is to evaluate the effectiveness of active reagents (i.e., methylene-bis(4-cyclohexylisocyanate) (HMDI) and 1,6-hexanediol diglycidyl ether (HDE)) and epoxidized soybean oil (ESO) in rejuvenating aged styrene-butadiene-styrene (SBS)-modified asphalt binder (SBSPAV) by promoting the interaction of aged binders with virgin asphalts. To achieve this objective, a multidisciplinary approach combining chemical and engineering methods was adopted. The chemical characterization of asphalt binders includes SARA fractionation (saturates, aromatics, resins and asphaltenes) and Fourier transform infrared spectroscopy (FTIR) tests. Rheological evaluation of the asphalt binders was utilized assessing fatigue, rutting, and thermal cracking resistance. The results indicated that the addition of ESO helped to adjust the low temperature performance of SBSPAV. Compared to SBS-modified asphalt (SBSMA), the low temperature relaxation modulus of ESO-rejuvenated asphalt has a 35.8% reduction. Whereas the addition of ESO alone could did not restore the performance of the SBSPAV. The addition of HMDI and ESO could improve the high-temperature performance of SBSPAV. Compared to SBSMA at 52 °C, the rutting factors of HMDI-rejuvenated asphalt with 0.5% and 1.0% were improved by 43.12% and 97.86%, respectively. According to the MSCR results, with a 1.0% content, the recovery rates of HDE-rejuvenated asphalt and HMDI-rejuvenated asphalt increased by 8.2% and −23.4%, respectively. The rejuvenated binders with HMDI showed better elastic recovery properties and permanent deformation resistance than the other studied binders. HMDI can increase the asphaltene content in rejuvenated asphalt, while HDE can increase the aromatic fraction content in rejuvenated asphalt, according to the SARA fraction results. The asphaltene content of 1.0% HMDI-rejuvenated asphalt increased by about 2.13%, and the aromatic content of 1.0% HDE-rejuvenated asphalt increased by about 3.46%. The FTIR results showed that HMDI chemically reacted with SBSPAV to form carbamate bonds with a stable chemical structure, and both HMDI and HDE could partially restore the broken chain structure of SBS. Overall, the results indicated that HMDI and HDE (combined with ESO) have the potential to be used to rejuvenate SBSPAV and that the recommended optimum contents for HMDI and HDE are 0.5%–1.0%. © 2022 Elsevier Ltd