Surface modified slag fiber reinforced asphalt mixture: Enhancement of pavement performance and field validation

The development of fiber reinforced asphalt mixture alleviates pavement distress and damage, extending the service life of asphalt pavements; however, the weak fiber/asphalt interface adhesion may limit its wider adoption in practical scenarios. We developed a fiber reinforced asphalt mixture utilizing slag fibers derived from solid waste as a novel solution for waste management. The surface of the slag fibers was modified with silane coupling agents to enhance the interface adhesion between the fiber and the asphalt matrix. Both molecular dynamics simulation and experimental results confirmed the effectiveness of the surface modification, showing increased interfacial compatibility and adhesion. The optimized fiber contents for asphalt mixtures were determined through Marshall tests, indicating that 0.3 wt% of modified short slag fiber or 0.4 wt% of modified long slag fiber yielded the most favorable results. The road performance of asphalt mixture was significantly improved, with increases of > 11.8 % in indirect tensile strength, > 22.5 % in dynamic stability, and > 10.7 % in flexural tensile strength at low temperatures. A great improvement in the stability of the asphalt mixture was achieved under varying temperatures. The robust fiber/asphalt interface allows stress to be easily transferred and enables the asphalt to be tightly absorbed by the fibers, stabilizing the asphalt mixture. After 10 months of service, field evaluations showed minimal deflection and few defects, confirming the practicality and durability of the modified slag fiber reinforced asphalt mixtures. This study offers a feasible and effective way to enhance asphalt pavement performance while addressing solid waste management issues.