Action mechanism of different active rejuvenators on the colloid structure of regenerated Styrene-butadiene-Styrene block copolymer modified bitumen: A perspective from Styrene-butadiene-Styrene block copolymer-bitumen interface

Abstract

The diglycidyl ether (HDDGE) and dicyclohexylmethane diisocyanate (HMDI) are widely adopted as active rejuvenators in the field of regenerated SBS modified bitumen (RSMB), which can react with the oxygen-containing functional group on the aged SBS, thereby rebuilding the crosslinking net of the SBS. Numerous measurements indicate that HDDGE negatively affects the high-temperature performance of RSMB, while HMDI impairs its low-temperature performance. This unexplained phenomenon continues to impede the effective regeneration of bitumen. To reveal the underlying mechanism of this phenomenon, this study investigates the SBS-bitumen interface inside the RSMB thought the molecular dynamics simulation, and conducts the experiments in the lab to prove the inference. Results indicated that the type and dosage of rejuvenators will affect the H-bonds inside regenerated SBS, which will change the configuration of SBS molecules. Subsequently, the regenerated SBS molecules will redetermine the fractions located at the SBS-bitumen interface thought the space steric hindrance effect and interaction between SBS and bitumen, which will alter the colloid structure of RSMB. This will significantly change the free volume of the RSMB, and will finally affect the macro-properties of RSMB.