Development of a Fatigue Testing Protocol for Asphalt Mixture Using Hamburg Wheel Tracking Device

The Hamburg Wheel Tracking Test (HWTT) has been widely accepted as a reasonable and reliable test to evaluate the rutting and moisture damage performance of asphalt mixtures. The standardized protocol for HWTT has been around under AASHTO Test Method T 324 for almost two decades. Several state DOTs and industries are now adopting this testing method as part of their routine testing protocols to verify the mix designs and to perform mixture performance evaluation. Some are also considering this testing protocol as part of their approach to a balanced mix design. However, for fatigue performance evaluation, there is still not a standard testing method that has been widely accepted by state DOTs as a routine testing method. In this study, it is proposed to develop and standardize a new fatigue test protocol that can evaluate the fatigue cracking resistance of the asphalt mixture in HWTT, with specific supporting conditions, so that an integrated design of material and structure can be achieved for use by the pavement industry. In addition, this test method should be practically feasible as a routine test method in terms of reliability, equipment availability, and data processing efficiency. The research in this work order will build upon the preliminary work conducted by the researchers to identify any test equipment modifications needed and to develop a draft testing protocol that is feasible and reliable. An important consideration will be to develop the test procedure in a way that the test can be completed within a reasonable level of time and number of cycles. The scope of work includes an initial evaluation of the HWTT in deciding the needed adjustments to the system to make it capable of conducting fatigue tests. This evaluation will be part of the test setup analysis and development of the experimental plan. Once the plan is developed and approved, the work will proceed to execution of the plan. The plan will consider the type of mixes to be studied, the temperature range, support conditions, number of wheel tracking cycles, the method of data collection, and the type of data to be collected. Development of the new fatigue testing protocol will be mainly based on the laboratory testing and evaluation of various mixes. During and after data collection, analysis of data will be conducted. This analysis includes investigating the relationship between fatigue cracking indices and mechanical responses from the test, so that proper fatigue failure criteria can be established from the test. Finally, a testing protocol along with final report will be developed and submitted. This scope of work includes five tasks.