Performance evaluation of waste melt-blown fibre and bio-oil composite modified asphalt binder

To overcome the limitation that single melt-blown fibre modification improves asphalt high-temperature performance but degrades low-temperature properties, this study proposes a composite modification strategy using waste melt-blown fibres (1%, 3%, 5%, and 7%) combined with 3% bio-oil to prepare melt-blown fibre/bio-oil composite modified asphalt (MBMA). Conventional tests, dynamic shear rheometer (DSR), bending beam rheometer (BBR), Fourier transform infrared spectroscopy (FTIR), and fluorescence microscopy (FM) were conducted to evaluate the rheological performance and modification mechanism. Results indicate that the optimal formulation consists of 5% melt-blown fibre and 3% bio-oil. Compared with base asphalt, ductility at 10 °C increases by approximately 129%, stiffness modulus at −18 °C decreases by 77%, and the rutting factor at 64 °C increases by 283%, while the viscosity at 135 °C (1031 mPa·s) satisfies workability requirements. The performance grade reaches PG76-34, demonstrating a balanced improvement in high- and low-temperature properties. FTIR analysis indicates that the modification is dominated by physical blending, and FM observations confirm uniform fibre dispersion at dosages not exceeding 5%. The addition of bio-oil replenishes light components, effectively alleviating the adverse low-temperature effects induced by fibres. This study provides a theoretical basis for recycling waste melt-blown fibres and developing dry-process asphalt modification technology.