Optimum moment to heal cracks in asphalt pavement by means of waste carbon fiber-enhanced electromagnetic induction heating during multiple damage-healing cycles

Abstract

This study investigated the optimal timing for healing asphalt pavement cracks using waste carbon fibers (WCFs) reinforced electromagnetic induction (EMI) technology through multiple "damage-healing" cycles, focusing on mechanical and fatigue performance. Initially, an extensive research project was carried out to evaluate the rate of induction heating, surface temperature decline rate, and effective heating depth of the asphalt mixture. Subsequently, from a mechanical performance perspective, semi-circular bending (SCB) tests were employed. By setting four different load termination conditions, the extent of cracking in the specimens was quantitatively controlled, followed by multiple "damage-healing" tests to analyze the impact of healing timing on the mechanical properties and healing efficiency of the asphalt mixture. Lastly, from the perspective of fatigue performance, using the four-point bending fatigue test (4 PB), the fatigue damage extent of specimens was quantitatively controlled through the attenuation rate of stiffness modulus. Multiple "damage-healing" tests were carried out at four different healing timings to study the effect of healing timing on the fatigue performance and healing efficiency of the asphalt mixture. The results indicated that WCFs improved the heating performance of asphalt mixture, enabling 5 cm-thick specimens to be fully heated within 6 min. Both SCB and 4 PB tests yielded similar conclusions: in the process of multiple "damage-healing" cycles, earlier healing interventions were beneficial for the recovery and maintenance of the mechanical properties of asphalt mixtures and effectively extended their service life. However, the fatigue tests also revealed that overly early self-healing interventions, where cracks were insufficiently formed, did not fully exploit the potential of the healing process. Conversely, healing interventions conducted too late were extremely detrimental to the restoration of mechanical characteristics and the prolongation of the asphalt mixture's lifespan.