Evaluation of various Hamburg wheel-tracking devices and AASHTO T 324 specification for rutting testing of asphalt mixtures

The Hamburg Wheel Tracking (HWT) laboratory test uses loaded wheel(s) to apply a moving load on asphalt mixture specimens to simulate traffic loading on asphalt pavements. Given that different machines with various degrees of compliance with the current AASHTO T 324 requirements are used by highway agencies, this study aimed to assess the capabilities of commercially available and representative HWT equipment, and to evaluate different analysis and reporting methods for rutting and stripping performance assessment. After performing a comprehensive evaluation of devices from different vendors, considerable discrepancies on equipment capabilities and configurations were identified. The machines did not meet all the requirements set forth in AASHTO T 324 including those for the wheel position waveform, the temperature range, and the reporting parameters. Evaluation of existing analysis methods revealed significant inconsistencies among different methods and deficiencies in the specification. Recommended modifications to the machines and test method were provided.