Performances of SBS and Nano-TiO2 Composite Modified Asphalt and Mixture after Repetitive Aging and Regeneration

Xuefeng Fan¹Shan Gang²Jianwei Fan²Fanlong Tang^3*

• ¹Jiangshan Highway and Harbor Transportation Management Center, Quzhou, China, Quzhou, China
• ²School of Transportation, Southeast University, Nanjing, China
• ³Jinling Institute of Technology, Nanjing, China

In this paper, the morphology and molecular weight of the modified asphalt components, high and low temperature performance of asphalt and mixture, moisture resistance, dynamic modulus and fatigue resistance of mixture were studied, so as to study the performance change law of SBS and nano-TiO2 composite modified asphalt and mixture after primary aging, primary regeneration, secondary aging and secondary regeneration. The results show that after repeated aging of composite modified asphalt, the SBS component degrades so its molecular weight decreases, and the asphalt component undergoes oxidation so its molecular weight increases. In the secondary regenerated asphalt, aged SBS chains are damaged and cracked, interweaving with the newly added complete SBS chains during regeneration. Nano-TiO2 remains basically unchanged during aging and regeneration. After repeated aging, the high-temperature performance of asphalt and mixture is significantly improved, while the low-temperature performance deteriorates severely and the moisture resistance slightly decreases. Compared to the original asphalt and mixture, the high-temperature performance of the regenerated asphalt and mixture is still higher, while the low-temperature performance is significantly lower. The residual stability after immersion is basically stable, and the freeze-thaw splitting strength ratio is reduced by 3.3% to 4.1%. The dynamic modulus of the mixture at the same frequency, in descending order, is secondary aging, primary aging, secondary regeneration, primary regeneration, and original asphalt mixture, while the order of the fatigue resistance is opposite. Overall, after repeated aging and regeneration, the SBS–nano TiO₂ composite modified asphalt and mixtures consistently exhibit superior high-temperature performance compared to the original state, while low-temperature and fatigue performances show a declining trend. Regeneration can partially restore these properties but struggles to reach the original levels, providing a performance basis for the repeated reuse of composite modified asphalt.