Monitoring the Impact of Micro Cracks Healing Cycles on the Deformation of Asphalt Concrete Under Repeated Loading

Abstract

The micro cracks healing property in asphalt concrete is considered as a good start for understanding and controlling the durability issue of the pavement. However, the impact of repeated micro crack healing cycles have not been investigated thoroughly. In this work, cylindrical asphalt concrete specimens of 100 mm diameter and 63 mm height have been prepared in the laboratory using Marshall method. Specimens were divided into two groups. The first group was subjected to repeated indirect tensile stresses, while the second group was subjected to repeated double punch shear stresses (both at 25 °C) to initiate micro cracks within the specimens using controlled stress mode of loading for 0.1 s followed by rest period of 0.9 s for specified load cycles. Afterword, Specimens were subjected to external heating in an oven at 60 °C and allowed to heal for two hours, conditioned at 25 °C for two hours, then subjected to another course of repeated tensile or shear stresses. The healing process was continued for two successive courses of loading and heating. The deformation of the specimens was monitored through continuous video capture. The impact of asphalt content, type of test, and healing cycles on the permanent deformation have been analyzed. It was concluded that higher deformation of 16% could be detected under tensile stresses as compared to that under shear stresses. The healing cycles causes (7–30) % and (16–37) % reduction in permanent deformation under repeated (ITS) and repeated (PSS) respectively.