Three-Stage Damage Evolution of Asphalt Mixture in the Wet Hamburg Wheel Tracking Device Test Using X-Ray Computed Tomography

AbstractThe Hamburg wheel tracking device (HWTD) test is widely used; however, limited research has been performed to fully understand the damage evolution of the asphalt mixture in the wet HWTD test. In this study, intuitive image analysis and air voids (AV) content analysis based on computed tomography (CT)-scanned samples confirmed and further supplemented the failure pattern of the HWTD testing specimens in three stages. The results indicate that the change in the calculated AV content and 3D reconstructed AV images from the CT analysis correlated well with the responses of the HWTD testing samples at different stages. Additionally, the decrease in closed voids in the sample can be used as an indicator of both the integrity of the specimen and the degree of damage in the HWTD test. Further, it was found that the optimum binder content determined by the wet HWTD test can reflect both the rutting resistance and moisture sensitivity of the HMA. The HWTD test is recommended as a pass/failure criterion during the design process of asphalt pavement.