Performance Evaluation of Biochar-Modified Bitumen: Physical, Rheological, and Short-Term Aging Characteristics

Petroleum-based bitumen binders face increasing sustainability challenges due to aging, rutting susceptibility, thermal sensitivity, and their high carbon footprint. Biochar, a carbon-rich material produced through biomass pyrolysis, has emerged as a promising waste-derived modifier capable of enhancing binder performance while supporting circular economy principles in pavement engineering. This research investigates the effects of incorporating 5%, 10%, and 15% biochar into C600 bitumen on its physical, rheological, and short-term aging properties. Binder performance was evaluated using penetration, softening point, and viscosity tests at 135°C and 165°C. Rheological properties were assessed using a Dynamic Shear Rheometer (DSR) to determine the complex shear modulus (G*), phase angle (δ), and rutting parameter (G*/sinδ), together with the Multiple Stress Creep Recovery (MSCR) test. Short-term aging performance was evaluated using the Thin Film Oven Test (TFOT). The physicochemical characteristics of the biochar were characterized using Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), and Brunauer–Emmett–Teller (BET) analysis. The results showed that biochar improved the physical, rheological, and short-term aging performance of C600 bitumen. Compared with the control binder, the 10% biochar-modified binder exhibited a 27% reduction in penetration and a 7% increase in softening point, indicating enhanced binder stiffness and improved high-temperature performance. Biochar addition also increased binder viscosity and enhanced resistance to short-term aging following TFOT. Based on the MSCR results, the 10% biochar-modified binder achieved the High (H) traffic grade, demonstrating superior rutting resistance, whereas the 15% biochar-modified binder was classified as the Standard (S) traffic grade, indicating that 10% biochar provided the optimum overall performance. The findings demonstrate the potential of biochar as a sustainable waste-derived modifier for improving the high-temperature performance and aging resistance of bitumen. Further research should focus on low-temperature performance, long-term aging behaviour, field validation, and life-cycle assessment to facilitate practical implementation in sustainable pavement applications.