Laboratory evaluation of ultraviolet aging performance of regenerated SBS modified bitumen based on active flexible rejuvenators with different molecular structures

Active flexible rejuvenators achieved high-quality regeneration of aged SBS modified bitumen (SMB) by reconstructing the aged SBS cross-linked structure while also an incorporating bitumen component reducing agent (aromatic oil, AO). However, the impact of active flexible rejuvenators with different molecular structures on the ultraviolet (UV) radiation durability of regenerated SBS-modified bitumen remains unclear, making it impossible to evaluate the long-term effectiveness of these rejuvenators. In this study, aged SMB was subjected to composite regeneration using active flexible rejuvenators with different molecular structures and AO. Subsequently, the regenerated SMB was subjected to UV aging. By comparing it with SMB regenerated with only AO, the influence of active flexible rejuvenators with different molecular structures on the UV aging properties of the regenerated SMB was investigated. FTIR results revealed that the SBS cross-linked structure, which had been reconstructed by the active flexible rejuvenators, underwent continued degradation and breakage during UV aging. This process consumed UV radiation energy and oxygen, thereby partly inhibiting the oxidative condensation of the regenerated bitumen. The SARA fractions analysis indicated that active flexible rejuvenators could slow down the volatilization of light components and their rate of oxidative condensation during UV aging by reconstructing the aged SBS cross-linked structure. The incorporation of active flexible rejuvenators mitigated the deterioration of the physical and rheological properties of the regenerated SMB subjected to UV radiation. When utilized in comparison to solely employing bitumen component reducing agents, active flexible rejuvenators were capable of bolstering the aging resistance of SMB that had underwent regeneration by reconstructing the cross-linked structures of aged SBS. The effectiveness of active flexible rejuvenators in enhancing the aging resistance of SMB during regeneration varies, owing to their differing sensitivities to ultraviolet radiation based on their molecular structures. This study offered data support for optimizing the molecular structure of active flexible rejuvenators. • Reconstructed SBS molecular structure enhanced UV aging resistance of bitumen. • The sensitivity of active flexible rejuvenators varied in response to UV radiation. • AFRs impeded the performance degradation rate of regenerated SMB during UV aging.