Influence of Aging, Temperature and Moisture Damage on the Stiffness of Asphalt Concrete through the Fatigue Process

Abstract

The stiffness of asphalt concrete is considered as a key element in the fatigue process under load repetitions. In this study, an investigation was made in order to better understand the influence of long term aging, moisture damage, low testing temperature, asphalt content, and Microstrain level on the stiffness through the fatigue process of asphalt pavement. Repeated four-point flexure bending beam test in controlled strain mode has been implemented using Nottingham apparatus. Asphalt concrete mixtures were prepared using different percentages of asphalt cement, (optimum and 0.5% above and below the optimum). Asphalt concrete slab samples of (300x 400x 60) mm were prepared using roller compaction, beam specimens of (400x 50x 60) mm were cut from the slab samples. Beam specimens were divided into four groups, the first group was tested for fatigue life under the influence of three levels of micro strain (750, 400, and 250). The second group was tested at 30, 20, and 5 °C, while the third group was subjected to long-term aging, before testing for fatigue life. The fourth group was subjected to moisture damage impact, and then tested for fatigue life. The changes in stiffness per load cycles have been monitored. It was concluded that the stiffness is susceptible to moisture damage and aging, the increase in Microstrain level leads into a remarkable decrease in initial and failure stiffness's. The stiffness is susceptible to the testing temperature and asphalt content, lower testing temperature of 5o C exhibits higher stiffness value, while higher binder content has a negative impact on the stiffness.