Comparative Investigation of the Rheological Properties and Rejuvenation Mechanism of Rejuvenated SBS Modified Asphalt Binder After Ultraviolet Aging

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.