Aging Resistance Performance and Mechanisms of SBS-Modified Bitumen Enhanced with Carbon Nanomaterials

Bitumen modified with styrene–butadiene–styrene copolymer (SBS) is susceptible to thermal-oxidative aging during service, compromising its long-term durability. Carbon nanomaterials exhibit the potential to inhibit oxidative degradation of bitumen and enhance resistance to aging. However, the synergism mechanism of aging resistance in the use of carbon nanomaterials and SBS in bitumen composites is still unclear. This study investigated the mechanisms through which graphene and carbon nanotube (CNT) enhance the durability of SBS-modified bitumen. This study also systematically compared and analyzed the aging resistance of SBS-modified bitumen, bitumen with hybrid CNT/SBS, bitumen with hybrid graphene/SBS, and bitumen with hybrid graphene/CNT/SBS. The results show that the incorporation of carbon nanomaterials significantly reduces the chemical aging index and the rheological aging index of SBS-modified bitumen, thereby markedly improving its aging resistance. These are the main antiaging mechanisms: Carbon nanomaterials form a three-dimensional barrier network in SBS-modified bitumen. This network effectively inhibits oxygen diffusion and ultraviolet penetration. It delays chain-scission degradation of SBS and oxidative hardening of bitumen, thereby maintaining the integrity of the modified network. In addition, the nanofillers restrict the thermal motion of molecular chains through interfacial interactions. Bitumen with hybrid CNT/SBS exhibited the best aging resistance, and bitumen with hybrid graphene/SBS was second. This study systematically revealed the synergistic aging resistance mechanisms of carbon nanomaterials and SBS in bitumen composites. It provides theoretical support and performance evaluation for the engineering application of carbon nanomaterials in bitumen pavement infrastructure.