Investigation on Microwave-Activated Self-Healing Mechanisms in Asphalt Mixtures Under Single Damage Condition

Abstract

Asphalt pavement can self-heal through the flow of asphalt binder, which helps fill microcracks. However, in field conditions, this self-healing process is ineffective when there is no external application of heat. In addition to this, repeated traffic wears it down over time. To overcome this problem, adopting various methods to enhance the self-healing ability of asphalt mixtures is necessary for making pavements more sustainable. This study investigates microwave heating as an external stimulus to accelerate and enhance the self-healing process in asphalt mixtures. Microwave energy induces rapid volumetric heating, which enhances asphalt binder mobility by reducing its viscosity, thereby facilitating rapid and effective crack closure. The objective of this research is to evaluate the self-healing efficiency of asphalt mixtures using microwave heating at a single and controlled damage degree under varying healing temperatures. The scope of this study encompasses a literature review, material characterisation, and laboratory investigation through multiple fatigue–healing cycles, with a focus on fracture-based recovery. A systematic experimental program was conducted using the Semi-Circular Bending (SCB) test to induce a predefined degree of damage in asphalt mixture specimens. After applying damage, specimens were heated in a microwave at selected healing temperatures and subsequently re-tested using the SCB method. Healing efficiency was measured based on the recovery of fracture parameters measured before and after the healing process, both with and without heating application. The findings indicate that microwave heating significantly enhances the healing efficiency of asphalt mixtures, and the healing temperature has a significant effect on crack recovery. However, an increase in healing temperature after a certain limit resulted in deteriorated crack closure and mechanical restoration. Additionally, the effect of ageing on the self-healing of the asphalt mixture was carefully examined and considered in this comprehensive study. Overall, this study confirms the potential of microwave-induced self-healing as an efficient technique for extending the service life of asphalt pavements.