VARIABILITY IN THE HAMBURG WHEEL-TRACKING DEVICE (HWTD) DATA AND RESULTS

Over the years, the Hamburg Wheel-Tracking Test (HWTT) has become one of the most popular devices used for characterizing asphalt mixtures for rutting potential and moisture susceptibility. However, although the HWTT is a reliable standard test for evaluating asphalt mixtures, it is not exempt from variability in the test data and result. Variability in the HWTT test data and results have been majorly attributed to imprecision in the test practice and due to some limitations in the HWT device setup. The primary goal of this study is to evaluate the variability in the HWTT data and result by investigating a variety of asphalt mixtures. To achieve this goal, the merits and limitations of available HWTT analysis approaches are identified and investigated. Moreover, the study also compares the HWTT to Rotary Asphalt Wheel tester (RAWT) to primarily assess the level of variability in data and result. Furthermore, the performances of both comparable devices and the ability of the devices to distinguish between asphalt mixtures are investigated. Based on the results obtained from this study, a low to moderate level of variability was found in the HWT data and results. However, variability was seen to be greater in the HWT result compared to the RAWT results. Moreover, this study also shows that the RAWT could better discriminate between asphalt mixtures than the HWTT. Furthermore, by evaluating various analysis approaches, the study found that the Texas DoT three-parameter novel approach is the most robust method because the approach avoids the bias of the quality of data and eliminates subjectivity in the analysis