Electromagnetic Induction Heating-Activated Self-Healing of Asphalt Mastics with Alternative Fillers: Mechanical Recovery and Rheological Response

Electromagnetic induction heating (EIH) enables rapid thermal activation of self-healing asphalt, but the extent to which EIH susceptibility translates into a flow-capable condition, mechanical recovery, and subsequent rheological response remains insufficiently established at the mastic scale. This study therefore evaluated these relationships in eight mastics combining two binders (50/70 and PMB 45/80-65) with limestone, steel slag aggregate, metallic, and iron fillers. Preliminary EIH screening was followed by a formulation-specific flow-threshold procedure developed by adapting the ring-and-ball concept to localized induction heating. The resulting exposure times were transferred to a repeated fracture–healing–fracture protocol, followed by rheological characterization. Metallic- and iron-filler mastics showed the strongest EIH response and reached the flow threshold within 235–450 s, although heating rate alone did not predict flow time. After two EIH-assisted healing stages, 50/70-MF and 50/70-IF retained approximately 76–77% of their initial peak nominal tensile stress, compared with approximately 43% for the corresponding PMB mastics. Under the distinct, non-equivalent protocols adopted, the EIH-treated groups generally showed higher observed mechanical recovery than the corresponding Oven-treated groups while requiring substantially shorter active-heating periods. Rheological responses after the complete EIH- and Oven-based healing protocols were generally less pronounced than after adapted laboratory aging, while fatigue-damage testing was more sensitive to differences among the complete conditioning histories. Overall, effective EIH-assisted healing depended on electromagnetic susceptibility, flow behavior, and the mechanical/rheological response of the complete binder–filler system.