Impact of micro crack healing on resilient characteristics of asphalt concrete

Asphalt concrete is susceptable to cracking under repeated loading and various environmental conditions during its service life. This will impare the serviciability and durability of the pavement layers. Asphalt concrete mixtures can heal by themselves in slow process under repeated loading at ambient temperature. The micro cracks healing phenomena can increase the lifetime of asphalt treated layer for several years. The aim of this work was to investigate the impact of micro crack healing phenomena of asphalt concrete on the resilient characteristics under shear and tensile repeated stresses. Specimens of 100 mm diameter and 75 mm of height have been prepared at optimum asphalt content, and at 0.5% asphalt above and below the optimum. Specimens were devided into two groups, the first group was subjected to repeated indirect tension, while the second group was subjected to repeated punching shear stress. Both testing techniques were conducted using the Pneumatic repeated load system (RPLS) at 25 ° C for 20 minutes at three constant stress levels to allow for the initiation of micro cracks. Specimens were withdrawn from the testing chamber and stored in an oven for 120 minutes at 60 ° C to allow for crack healing. Specimens were subjected to another cycle of repeated tensile or shear stresses at 25 ° C for 20 minutes. Another healing process was conducted on the specimens. The deformation of the specimens under repeated indirect tensile or shear stresses was captured using video camera for both conditions. The impact of crack healing was detected through the variation of the resilient characteristics under three levels of stress application before and after healing.