Hamburg Wheel-Track Test Equipment Requirements and Improvements to AASHTO T 324 (2016)

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1 Table of Contents 1. Summary ........................................................................................................................................ 3 2. Introduction and Research Approach ............................................................................................. 5 2.1. Problem Statement.................................................................................................................. 5 2.2. Research Objective ................................................................................................................. 6 2.3. Research Approach ................................................................................................................. 6 2.3.1 Task 1 – Available Hamburg Test Equipment Specifications ........................................ 6 2.3.2 Task 2 – Engineering Desk Analysis of Existing Hamburg Test Systems ..................... 6 2.3.3 Task 3 – Propose Revisions to AASHTO T 324 ............................................................ 7 2.3.4 Task 4 – A Framework for Future Laboratory Evaluation ............................................. 7 2.3.5 Task 5 – Prepare and Submit Final Report ..................................................................... 7 3. Methodology and Experimental Program ...................................................................................... 8 3.1. Review of Test Equipment Specifications .............................................................................. 8 3.2. Nationwide Survey ................................................................................................................. 8 3.3. Experimental Program ............................................................................................................ 8 3.3.1 Wheel Position Waveform, Frequency, and Maximum Speed ....................................... 9 3.3.2 Impression Measurement System ................................................................................. 12 3.3.3 Temperature Control System ........................................................................................ 16 3.3.4 Wheel Dimensions ........................................................................................................ 17 3.3.5 Wheel Loads ................................................................................................................. 18 3.3.6 Specimen and Track Length ......................................................................................... 18 3.3.7 Free Circulating Water on Mounting System ............................................................... 19 3.3.8 Data Collection and Reporting ..................................................................................... 20 4. Results and Analysis .................................................................................................................... 21 4.1. Review of Test Equipment Specifications ............................................................................ 21 4.1.1 Loading Mechanism ..................................................................................................... 24 4.1.2 Wheel Speed ................................................................................................................. 24 4.1.3 Temperature Measurement and Control System .......................................................... 25 4.1.4 Impression Measurement System ................................................................................. 25 4.1.5 Specimen Length and Track Length ............................................................................. 25 4.1.6 Data Collection and Reporting ..................................................................................... 25 4.2. Findings of the Nationwide Survey ...................................................................................... 26

2 4.2.1 Type of HWTs Used ..................................................................................................... 27 4.2.2 Test Methods Used ....................................................................................................... 27 4.2.3 Test Temperature .......................................................................................................... 28 4.2.4 Mix Acceptance Criteria ............................................................................................... 29 4.2.5 Reporting of Test Results ............................................................................................. 30 4.3. Wheel Position Waveform, Frequency, and Maximum Speed ............................................. 30 4.3.1 Test Results .................................................................................................................. 30 4.4. Experiment I – Wheel Dimensions ....................................................................................... 36 4.5. Experiment II – Wheel Loads ............................................................................................... 38 4.6. Experiment III – Free Circulating Water on Mounting System ........................................... 39 4.7. Experiment IV – Temperature Measurement and Control System ...................................... 39 4.7.1 Evaluation at 50°C ........................................................................................................ 40 4.7.2 Evaluation at 25°C ........................................................................................................ 45 4.7.3 Evaluation at 70°C ........................................................................................................ 48 4.8. Experiment V – Impression Measurement System .............................................................. 51 4.8.1 Test Results .................................................................................................................. 52 4.9. Data Collection and Reporting ............................................................................................. 56 4.9.1 Test Materials ............................................................................................................... 58 4.9.2 Results and Analysis ..................................................................................................... 58 4.10. Proposed Modifications to AASHTO T324 Specifications .............................................. 63 4.11. Laboratory Experimental Plan for Validation of Proposed Changes ............................... 65 5. Conclusions and Recommendations ............................................................................................. 66 5.1. Recommendations ................................................................................................................ 67 6. References .................................................................................................................................... 68 7. Appendix A .................................................................................................................................. 70 8. Appendix B .................................................................................................................................. 76 9. Appendix C .................................................................................................................................. 78 10. Appendix D .................................................................................................................................. 82