Microwave heating characteristics of asphalt mixtures containing rejuvenator-loaded fibers for self-healing purposes

Microwave heating has emerged as an effective method to promote the self-healing process of asphalt pavements by controlling the temperature conditions required for effective repair. Nevertheless, the microwave thermal response of asphalt mixtures containing encapsulated rejuvenators has not been fully characterized. In this study, the microwave heating characteristics and their correlation with the self-healing behavior of asphalt mixtures containing rejuvenator-loaded fibers were systematically investigated. The critical self-healing temperature was determined via frequency sweep tests conducted using a dynamic shear rheometer. Infrared thermography was then employed to examine temperature distribution and evolution during microwave heating and subsequent natural cooling. Two novel indicators—healing duration and healing energy—were introduced to correlate thermal-temporal parameters with self-healing potential. Results showed that the critical self-healing temperature decreased with increasing asphalt penetration grade and was slightly lower than the corresponding softening point. The incorporation of rejuvenator-loaded fibers enhanced microwave heating rate and improved temperature uniformity. A minimum irradiation time of 40 s was required for effective self-healing. The majority of healing occurred during the cooling phase rather than during microwave irradiation. Extended microwave irradiation time was the critical factor in cold environments, while employing a high fiber content was highly advantageous in warm environments. These findings provide a theoretical foundation for designing energy-efficient microwave-responsive asphalt pavements with enhanced durability.