Novel composite rejuvenators development and comparative analyses of epoxy versus diisocyanate rejuvenators in rejuvenating aged SBS-modified asphalt binders

Currently, many high-grade highways are undergoing expansion and remodeling phases. Utilizing recycled Styrene-Butadiene-Styrene (SBS) modified asphalt mixtures not only increases waste material utilization but also offers significant environmental benefits. In pursuit of high-quality rejuvenation of aged SBS-modified asphalt binders (SBSMA), this research leveraged aromatic oil (AO) as the component rejuvenator and introduced two novel SBS rejuvenators: ethylene glycol diglycidyl ether (GDE) and isophorone diisocyanate (IPDI). Furthermore, the study explores the mechanisms and effectiveness of both epoxy and diisocyanate rejuvenators, which are commonly used in SBS rejuvenation, specifically focusing on reconstructing cross-linked network structures within rejuvenated SBSMA. Findings indicate that during rejuvenation with diisocyanate rejuvenators and AO, the amide groups effectively react with carboxyl and ester groups in aged SBS, thus reconstructing the SBS modifiers. The rejuvenated SBS subsequently absorbs AO and light components, leading to swelling and the reconstruction of cross-linked network structures. Nevertheless, the rejuvenation efficacy of epoxy rejuvenators was relatively limited due to their low reactive nature or adverse side reactions that could degrade the rejuvenated SBS molecules, resulting in less effective reconstruction of the network structure. The specific differences in the reconstruction of network structures were reflected that diisocyanate rejuvenators improved the road performance of rejuvenated SBSMA under both high and low temperatures, reaching or even surpassing unaged SBSMA, while the performance of epoxy rejuvenators was closer to that achieved using AO alone. Overall, diisocyanate rejuvenators outperformed epoxy rejuvenators in repairing SBS, significantly enhancing the performance of SBSMA. This study provides valuable insights into achieving high-quality rejuvenation of SBSMA, which can significantly enhance the efficiency and quality of rejuvenation in high-grade roadways.