| This thesis examines AASHTO T 283 and Hamburg (OHD L-55) Wheel Track test methods on determining hot mix asphalt (HMA) moisture damage. AASHTO T 283 is one of the most widely accepted test methods to identify moisture susceptible HMA. However, because of its poor repeatability and the time it takes to complete the procedure, it was desired to determine if it could be replaced by the Hamburg test. In order to meet the objective, laboratory compacted and plant produced samples were used. Mixes were selected based on their need of anti-strip. Mixes that required anti-strip to pass AASHTO T 283 were tested with and without anti-strip at optimum asphalt content. Mixes that did not require anti-strip were tested at optimum asphalt content, with 0.5% extra asphalt, and foamed. All mixes were tested in accordance with AASHTO T 283 and OHD L-55 test procedures. According to the test results, the Hamburg test at 20,000 passes did a better job of identifying mixes that failed AASHTO T 283 and at detecting the presence of 0.5% extra asphalt. However, this would make OHD L-55 a more severe test than it currently is. Comparisons were made between laboratory and plant produced test results for the two test methods. The Hamburg test method showed high variability, which raised repeatability concerns. In order to check repeatability of the Hamburg, five replicate samples were prepared and tested. Results were recorded at 10,000 and 15,000 passes. There was a significant difference in the results recorded at 15,000 passes but not at 10,000 passes. The Hamburg test method needs a thorough evaluation of its repeatability. The Hamburg test failed to successfully identify mixes that failed AASHTO T 283. Therefore, the Hamburg test method is not recommended to replace AASHTO T 283. |
