Effect of MA-EPR-ESO Compound Rejuvenator on Rheological Properties of Aged SBS-Modified Bitumen

The rejuvenation of aged styrene-butadiene-styrene–modified bitumen (SBSMB) can be achieved by adding a compound rejuvenator, consisting of maleic anhydride (MA), epoxidized polybutadiene resin (EPR), and epoxidized soybean oil (ESO). However, the optimal combination of this compound rejuvenator dosage was determined according to traditionally physical property indicators, so the obtained optimal combination may be imprecise. In this research, the rejuvenation effects of the compound rejuvenator were demonstrated based on physical property indicators. Then, to accurately obtain the optimum combination of the compound rejuvenator, a three-factor versus three-level (MA dosage levels were 0.05 %, 0.1 %, and 0.2 %; EPR dosage levels were 1 %, 2 %, and 3 %; ESO dosage levels were 4 %, 6 %, and 8 %) orthogonal scheme was designed. The rejuvenation effects of aged SBSMB were evaluated by rheological properties of rejuvenated SBSMB, and the optimal combination of the compound rejuvenator was obtained based on the continuous performance grade (PG) of the rejuvenated SBSMB at different dosage combinations. Finally, the rejuvenation effects of the optimal combination were verified by physical properties and fluorescence microscope tests. The results suggest that the preselected dosage combination of the compound rejuvenator can recover the base bitumen from its aged state (brittle and hard) and may repair the broken SBS fragments. The influence magnitude of the three components on the rheological properties of aged SBSMB is ESO, EPR, and MA in order. When the addition dosages of MA, EPR, and ESO are 0.2 %, 2 %, and 4 %, respectively, the rejuvenated SBSMB has similar physical and rheological properties with the original SBSMB. In addition, the FM result shows that the homogeneous distribution SBS network structure of SBSMB, which is destructed during long-term aging, is effectively recovered by the addition of the optimal combination of the compound rejuvenator.