Novel Method for Moisture Susceptibility and Rutting Evaluation Using Hamburg Wheel Tracking Test

The Hamburg wheel tracking test (HWTT) has been widely used as a standard laboratory test to evaluate the moisture susceptibility and rutting resistance of asphalt mixtures. The stripping inflection point and the rut depth at a certain number of load cycles are two common parameters obtained from the test. Although these parameters have been widely adopted by several transportation agencies, the accuracy and variability in characterizing mixture properties of these parameters have been questioned. In this study, a novel method to analyze the HWTT results is introduced and three new parameters are proposed to measure the moisture susceptibility and rutting resistance of asphalt mixtures. The new parameters are compared against the current ones to assess their capability to discriminate between three types of asphalt mixtures with different performance results in the HWTT. Significant advantages in characterizing mixture resistance to stripping and rutting are demonstrated by the new parameters. In addition, the effect of anti-stripping additives and recycled materials on mixture performance in the HWTT is evaluated with mixtures from a field project in Texas. Test results for the new parameters show that the addition of antistripping additives improves the susceptibility of asphalt mixtures to moisture. Specifically, the use of lime is more beneficial for improving mixture performance than a liquid antistripping agent. Conversely, the addition of recycled materials provides mixtures with increased moisture susceptibility but improved rutting resistance.