Self-healing degradation of asphalt concrete materials due to cooling cycles

Asphalt concrete is one of the most widely used materials in transportation infrastructure, covering the surface of approximately 94% of more than 4 million miles of highways in United States. Self-healing is an intrinsic property of asphalt material, which can reverse the cracking process in asphalt pavements and therefore extend their pavement service life. The present study utilizes an Acoustic Emission (AE) approach to provide quantitative assessment of self-healing of thermally induced cracks in asphalt concrete materials. Asphalt concrete specimens were subjected to eight cooling cycles and effects of resting time between cooling cycles on self-healing were investigated. The AE test results showed gradual degradation in self-healing capability of asphalt mixtures as the material was exposed to increasing numbers of cooling cycles. However, it was also observed that the rate of self-healing degradation was not constant as it was higher at beginning and then gradually reduced until it reached almost zero after the fourth cooling cycle. Moreover, AE results also indicated that the 12 hours of resting time between cooling cycles significantly increased the self-healing by more than 30% and allowed the material to regain most of its self-healing capabilities.