Feasibility of implementing Active Acoustic Emission (AAE) Technology to Monitoring the Crack Healing Process of Asphalt Concrete (AC)

Active Acoustic Emission (AAE) is a non-destructive test (NDT) technique used for monitoring crack initiation detection and the progress of internal damage at the microscopic scale. In this assessment, specimens of asphalt concrete (AC)were prepared with optimum binder requirements using Marshall method. Specimens were tested for fatigue using PRLS (pneumatic repeated load system) at 20°C environment and monitored through AAE technology. Dynamic indirect tensile stress (DITS)was applied to the diametral specimen, and the vertical strain is recorded after each load repetition. A constant loading frequency of 60 cycles per minute was applied. Each load cycle is 0.9 sec rest period and 0.1 sec load duration. The ultrasound pulse velocity (USPV)after 600 and 1200 load repetitions was recorded. Testing was terminated after 1200 load repetitions, and the specimens were withdrawn from the PRLS chamber and stored in an oven at 60 °C for 120 minutes to allow microcrack healing. Specimens were returned to the testing chamber and subjected to second round of load repetitions. It was observed that the USPV declined after practicing 1200 repetitions of indirect tensile stresses by (26, 14.2, and 12.3) % for wearing, binder, and base courses mixtures respectively as compared with their control mixtures. However, after practicing crack healing, USPV increased by (13.5, 25.8, and 2.3) % for wearing, binder, and base courses mixtures respectively. Deterioration of the mixtures was monitored through AAE technology and modeled. AAE technology is recommended for prediction the damage behavior of AC through its fatigue life.