Prediction of bituminous mixture fatigue life based on accumulated strain

This research was aimed to predict the number of cycles that cause fracture of hot-mix asphalt (HMA) based on the number of cycles at which the slope of accumulated strain switched from decreasing to increasing mode. In addition, the effect of aggregate gradation and temperature on fatigue behaviors of HMA were evaluated.HMA specimens were prepared at optimum asphalt content using the Marshall mix design procedure. The specimens were prepared using crushed limestone aggregate, 60/70 penetration asphalt, and three different aggregate gradations with maximum nominal aggregate size of 12.5, 19.0, and 25.0 mm. Five magnitudes of load (1.5, 2.0, 2.5, 3.0, and 3.5 kN) were evaluated for their effect on fatigue behavior.Constant stress fatigue tests were performed using the Universal Testing Machine (UTM) at 25 °C. Other temperatures (10, 45, and 60 °C) were evaluated at a load of 3.5 kN.The tests results indicated that the slope of accumulated strain continued to decrease until the number of loading cycles approached 44% of the number of cycles that caused fracture of the HMA. Also, the initial stiffness of asphalt mixtures was found to increase as the magnitude of the load applied increased and as the aggregate gradation maximum nominal size decreased.