Cracking features of asphalt mixtures under induced heating-healing

This research presents effects of induced heating-healing process on fracture properties and life extension of asphalt mixtures. Induced heating-healing technique is an innovative technique to repair damages and heal cracks in asphalt mixtures, implementing an external electromagnetic field to raise temperature of asphalt mixture. Temperature rising results in melting and flowing of asphalt binder between crack edges, healing cracks, and recovering internal strength of asphalt mixture lost during service life. Previous researchers considered different criteria to quantify induced healing efficiency in asphalt concrete, resulting in substantial differences. Nevertheless, conclusions presented by previous researchers are not comparable due to different materials, heating, healing, and testing conditions. Hence, a further study is needed to identify induced healing effectiveness based on asphalt mixtures form different binder grades. In this study, activated carbon modified and unmodified asphalt binders were utilized to prepare asphalt mixtures. Then, a cyclic heating-healing scenario under semi-circular bending (SCB) test was conducted at intermediate and low temperatures. Values of the fracture criteria (i.e., peak load, stress intensity factor, stiffness, strain energy, critical strain energy release rate, and fracture energy) were quantified at each cycle. Besides, extensions of fatigue and thermal fatigue lives obtained via induced healing process were characterized. Comparing results of modified and unmodified mixtures indicates that activated carbon significantly improves efficacy of induced healing. Additionally, induced healing process leads to different effects on different crack features. Moreover, induced healing efficiencies obtained based on fatigue and thermal fatigue extensions are approximately similar to that of peak load criterion. This study indicates that to evaluate effects of induced heating-healing process on improvement of different mechanical behaviors in asphalt mixtures over service life, corresponding crack property (criteria) needs to be considered.