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https://www.nationalacademies.org/trb/events

Evaluation of Hamburg Wheel Tracking Test (HWTT) for Rutting Resistance Assessment

The primary objectives of this project are to determine if the Hamburg Wheel Tracking Test (HWTT) test accurately represents rutting and stripping behaviors of fine-graded asphalt pavement design mixtures, and make appropriate adjustments to the HWTT criteria and/or propose and develop a representative rutting test that allows Wisconsin Department of Transportation (WisDOT) to retain the benefits of fine-graded mixes while supporting the state’s goal of fully implementing balanced mix design concepts. WisDOT expects to use the results and recommendations of this research study to support the acceptance of performance-based asphalt pavement designs. Practical candidate test procedures must also be considered for production. WisDOT has conducted significant external and internal research efforts in the past several years toward the implementation of Balanced Mix Design (BMD) to improve the performance of asphalt mixtures in Wisconsin. Based on experience, WisDOT has observed a tendency of the HWTT to rank fine-graded mixtures as having more rutting potential than coarse-graded mixtures. This tendency is noticeable even when rutting in the field is not a primary concern regarding the performance of fine-graded mixtures. A reliable BMD performance test is expected to be sensitive to changes in mixture components, but it also should have a good correlation with the field performance. Because the current rutting performance of fine-graded mixtures in Wisconsin is satisfactory, WisDOT does not want to implement the BMD approach using the HWTT as a rutting performance indicator if the test is going to lead mixture designers to develop coarser gradation mixture designs. It is, therefore, critical for WisDOT to investigate what factors drive HWTT results and understand how BMD specifications could be written to allow for finer mixtures while properly representing their field performance.