Mitigating the Degradation of Microwave Self-Healing Efficiency in Asphalt Mixtures under Water Damage and Freeze–Thaw Cycles via Silicon Carbide Aggregates

To assess the potential of silicon carbide (SiC) as microwave-enhanced aggregates for improving the self-healing performance of asphalt mixtures, this study examined the influence of SiC particle size and substitution rate under water damage and freeze–thaw conditions. Microwave heating tests compared the thermal responses of SiC, steel slag, natural aggregates, and SiC-enhanced asphalt mixtures. Mixtures without SiC and those containing 25% by weight fine SiC were further evaluated for self-healing after water damage and freeze–thaw cycles. COMSOL simulations were used to analyze temperature distribution and energy utilization. Results show that SiC reached much higher temperatures than natural aggregates under microwave heating, and the optimal substitution rate was 25% by weight for fine SiC (0.075–2.36 mm), which increased the healing index by 17% and reduced water and freeze–thaw damage effects by 5.2 and 16.3%, respectively. Simulations indicated minimal temperature differences between SiC and surrounding aggregates, while energy utilization efficiency improved by 43% at higher SiC contents. These findings demonstrate that incorporating SiC can enhance microwave heating efficiency and mitigate performance loss caused by moisture and freeze–thaw in asphalt mixtures, highlighting its promise as a functional aggregate for durable, self-healing asphalt pavements.