Impact of Aging and Moisture on Fatigue Life of Asphalt Mixture

Abstract

Abstract In this study, the mechanical behavior of a dense-graded asphalt mixture subjected to unaged, short-term, and extended aged conditions along with one freeze-thaw moisture conditioning cycle was evaluated at two temperatures and three stress magnitudes. A stress-controlled repeated indirect tensile loading fatigue test with 0.1-s loading and a 0.4-s rest period was used for determining the fatigue life of asphalt mixture. Aging, moisture conditioning, and an increase in the test temperature adversely affected the tensile strength of the asphalt mixture. The reduction in stiffness modulus of asphalt mixture that was due to moisture conditioning increased with the increase in the level of aging. The ratio of conditioned to unconditioned stiffness modulus (stiffness modulus ratio) was noticed to be more sensitive to different aging conditions compared with the ratio of conditioned to unconditioned tensile strength (tensile strength ratio). The effect of aging on fatigue life of asphalt mixture reduced with the increase in stress from 450 kPa to 550 kPa and 650 kPa. Further, the fatigue life of asphalt mixture reduced with the increase in test temperature and moisture conditioning. The short-term and extended aged mixture had higher damage value at failure compared with the unaged mixture. The mean fatigue life represented by the scale parameter of Weibull distribution reduced with the increase in aging and moisture conditioning. Further, the reliability of fatigue life of short-term aged and extended aged asphalt mixture was lower than the unaged asphalt mixture. The fatigue model based on plateau value and fatigue life was found to be more accurate compared with other regression models considered. Statistical analysis showed that the critical combinations of factors that influenced the mechanical behavior of asphalt mixture were also dependent on the test type, which included the tensile strength test, stiffness test, and fatigue test.