Assessment of Deformation under Repeated Cracking-Healing Cycles of Asphalt Concrete

Abstract

The Asphalt concrete wearing course is subjected to direct tyre loading and practices distresses such as microcracks. However, asphalt pavement is known to exhibit self-healing ability of microcracks under repeated loading with rest period and controlled environment. In this work, the permanent deformation of the wearing course was assessed under repeated cracking and healing cycles. Asphalt concrete specimens of 100 mm diameter and 63 mm height have been prepared with optimum asphalt requirement and with additional 0.5% asphalt content above and below the optimum. Specimens were tested in the pneumatic repeated load system PRLS under repeated tensile and punching shear stresses at 25°C. A heavier sine pulse of 0.1 sec load duration and 0.9 sec rest period was applied. Specimens were subjected to 1000 load repetitions then allowed to heal by external temperature of 60°C for 120 minutes. The loading and the healing cycles were repeated three times. The crack healing was evaluated as a function of the reduction in permanent deformation under repeated tensile and shear stresses. It was observed that the permanent deformation decreases as the healing cycles increase regardless of the testing technique adopted. The variation of asphalt content was more significant under repeated tensile stresses as compared to the case under repeated punching shear stresses. The crack closure after the several cracking-healing periods was quantified by the (%) healing Index. It was concluded that the crack healing index (decrease in permanent deformation) of asphalt concrete increases by (20.6 and 25.8) % and (14.2 and 25) % after the second and third healing cycles when testing under repeated tensile and shear stresses respectively.