The regeneration performance of an aged styrene–butadiene–styrene block copolymer (SBS) will be significantly influenced by different rejuvenators. The objective of this study was to comparatively investigate the regeneration effect of different SBS-modified asphalt regenerators on aged SBS-modified asphalt. Four types of different regenerant formulations were selected. The optimal rejuvenator content was determined firstly using conventional performance tests. The rheological properties of the aged SBS-modified asphalt binder were evaluated by multiple stress creep recovery (MSCR) experiments. Subsequently, the regeneration mechanism of the SBS-modified asphalt binder was investigated using thin-layer chromatography–flame ionization detection (TLC-FID) and Fourier transform infrared spectroscopy (FTIR). The results showed that the rejuvenator had a certain recovery effect on the penetration, softening point, and ductility of the SBS-modified asphalt binder after aging. The SBS-modified rejuvenating agent was the most favorable among the four types of rejuvenators, where a rejuvenator dosage of 12% showed the optimal rejuvenation effect. The addition of regenerators could appropriately improve the elastic deformation capacity of the aged asphalt binder. The epoxy soybean oil in the regenerant reacted with the aging SBS-modified asphalt binder, supplementing the lost oil in the aged SBS-modified asphalt binder, dispersing the excessive accumulation of asphaltene, and making the residual SBS swell again. The viscoelastic properties of the aging asphalt binder were improved by adjusting the content of components and functional groups to achieve the purpose of regeneration.

This study aims to investigate the restorative effects and rejuvenation mechanisms of two rejuvenators on ultraviolet (UV)-aged SBS modified asphalt binder. Two types of rejuvenators were developed. The rheological properties of aged and rejuvenated asphalt were systematically evaluated using a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep and recovery (MSCR) tests. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were employed to analyze the rejuvenation mechanisms. The results demonstrate that UV aging significantly deteriorates both the high- and low-temperature performance of SBS modified asphalt binder. Oil-rich rejuvenator A effectively restores UV-aged asphalt’s high-temperature performance and low-temperature stiffness. Polymer-based rejuvenator B better repairs PAV-aged cross-linked networks with superior chemical dilution, but over-dilutes large molecules. Both comparably restore aged low-temperature performance, with rejuvenator A favoring stiffness recovery and rejuvenator B favoring m-value recovery. FTIR analysis reveals that aging significantly increases the carbonyl and sulfoxide indices of SBS modified asphalt binder, especially after PAV and UV aging. Rejuvenator B exhibits superior chemical dilution, reducing these indices nearly to their original levels. GPC analysis demonstrates an aging-induced molecular weight increase and large molecular size (LMS) formation. The recovery effect of rejuvenator A is quite limited (reducing LMS by 2%). Conversely, rejuvenator B aggressively reduces LMS but causes over-dilution. Overall, rejuvenator B is recommended to be used for aged SBS modified asphalt binder, especially after UV aging.