Interfacial and rheological characterisation of asphalt binder reinforced with titanate coupling agent-modified basalt fibre

Basalt fibre (BF) has been widely utilised in asphalt binder modification due to its outstanding mechanical properties, but its limited interfacial adhesion with bitumen hinders its reinforcing effectiveness. In this study, a titanate coupling agent (TCA) was employed to modify BF's surface to enhance its interfacial adhesion with the bitumen. Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy were used to analyse the surface chemical structure and microscopic morphology of BF and modified bitumen. Subsequently, rheological performance was evaluated using Dynamic Shear Rheometer and Bending Beam Rheometer under different fibre contents (0.5%, 1.0%, and 1.5%). Furthermore, the aging resistance of the modified bitumen was evaluated through rheological tests. The results indicated that TCA treatment induced the formation of Ti-O-Si bonds and ester groups on the fibre surface, significantly improving interfacial chemical bonding and fibre dispersion. Rheological tests revealed that the high-temperature rutting factor of TCA-BF modified bitumen at 1.5% content increased by 76.7% compared to the base bitumen, while the non-recoverable creep compliance decreased by over 50% and the creep stiffness modulus at −6°C reduced by 31%. Additionally, the fatigue life at 5% strain increased by 72%. Multiscale characterisation (FTIR, SEM, and rheological tests) indicated that the performance enhancement was associated with chemical bonding and improved fibre dispersion. TCA strengthens interfacial adhesion and promotes fibre dispersion through chemical anchoring, thereby enhancing bitumen's high-temperature stability, low-temperature cracking resistance, and fatigue performance. This study provides a theoretical foundation and practical implications for the development of highly durable and climate-adaptive fibre-reinforced asphalt binder materials.