Characterizing Fatigue Behavior of Asphalt Mixtures Utilizing Loaded Wheel Tester

Abstract

Although widely used by state Departments of Transportation (DOTs) and other highway agencies for characterization of rut resistance and moisture susceptibility of asphalt mixtures, loaded wheel testers (LWTs) are rarely employed to evaluate the fatigue performance of asphalt mixtures because of their inherent problems. In this study, LWT was used to characterize the fatigue behavior of asphalt mixtures. A commonly used type of LWT, an asphalt pavement analyzer (APA), was chosen as a platform and modified to conduct the fatigue testing. A linear variable differential transformer (LVDT) was mounted to the bottom of the specimen to measure the tensile strain on the bottom surface. The tensile stress was calculated by treating the test specimen as a simply supported beam with a vertical load moving on its top. With the stress and strain measurements, theoretical analyses could be made to characterize the fatigue properties of asphalt mixtures. For comparison purposes, two other types of fatigue tests, beam fatigue and direct tension fatigue tests, were also conducted. Four types of asphalt mixtures were tested for their fatigue characteristics using the three fatigue tests. Two types of approaches—stiffness and dissipated energy—were adopted to analyze the fatigue behavior of asphalt mixtures. The results showed that LWT fatigue test was able to differentiate between asphalt mixtures in terms of fatigue behavior. The results from the LWT fatigue test were generally consistent with those from flexural beam and direct tension fatigue tests. The LWT fatigue test has the potential to become a useful tool to rationally characterize fatigue properties of asphalt mixtures and to differentiate good-performing from poor-performing mixtures in terms of fatigue resistance.