Sustainable microwave-heating healing asphalt concrete fabricated with waste microwave-sensitive fillers

The use of waste fillers as substitutes for limestone powder (LP) filler is a promising way to consume industrial by-products and achieve sustainable asphalt pavement. This study recycles three types of microwave-sensitive fillers, namely, coal gangue powder (CGP), ferrite powder (FP), and fly ash (FA), as alternatives to LP filler, in the creation of microwave-heating healing asphalt composites. The results indicate that conventional LP-modified asphalt mastics have a self-healing initiation temperature of 88.2 °C. On the contrary, CGP-modified asphalt mastics and FP-modified asphalt mastics exhibit significantly lower starting self-healing temperatures, with values of 65.6 °C and 56.2 °C, respectively. Moreover, CGP-modified asphalt mastics and FP-modified asphalt mastics achieve an average surface temperature surpassing 95 °C within 60 s of microwave heating. It is worth noting that FP-modified asphalt mastics retain an impressive healing index of 46.6% even after three cycles of damage-healing-damage. The incorporation of microwave-sensitive fillers in asphalt composites can improve the conversion efficiency of microwave radiation to thermal energy, and thus enhance the microwave-heating healing characteristics compared to conventional LP-modified asphalt composites. Additionally, a comprehensive assessment of the environmental benefits and economic costs reveals significant cost savings and reductions in CO₂ emissions associated with the adoption of microwave-heating healing asphalt pavement. These findings strongly support the practical implementation of microwave-sensitive fillers in asphalt composites, leading to improved maintenance efficiency, enhanced serviceability, and sustainability for pavement systems.