United States Department of Transportation
i
Balanced Asphalt Concrete Mix Performance in Utah. Phase V: Field Evaluation for Intermediate and Low-Temperature Cracking
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2021-07-01
[PDF-4.08 MB]
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Edition:Final Report
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Abstract:A follow-up study was conducted in which the performance of five asphalt pavements was documented after three years of field service in Utah. Cores were taken at each pavement section and brought to the lab where they were cut and tested using the BBR, the IFIT, and the IDEAL CT. The respective performance indices from these tests were compared to the previous results obtained from the loose mix obtained at the time of construction. The predicted performance from the original study was compared to the actual performance of the pavement sections. Based on the test results from laydown material, it was found that the BBR was correct in predicting poor low-temperature performance and the IFIT was also able to predict poor intermediate temperature performance. These results can help in setting a threshold that new mixtures must meet for good performance. For the BBR, a maximum creep modulus of 12,000 MPa and a minimum m-value of 0.12, at the expected environmental conditions, were found. Furthermore, the effect of aging should be considered. For the FI a minimum value of 8 at 25 ºC was found, and, based on a relation between the FI and the CT Index, a minimum CT Index of 125 to 150 was estimated. Finally, the chemical changes of standard asphalt mixtures from aging and the introduction of RAP were studied using FT-IR and SEM. The results showed an inverse relation between the formation of certain chemical groups produced from the oxidation of the material and the mechanical properties. The final conclusion of this study was that mechanical tests such as the BBR at low temperatures and the IDEAL CT at intermediate temperatures performed on recently produced asphalt mixtures can predict those sections that are likely to show poor performance. It is recommended that such tests be adopted as part of the asphalt mixture design process within UDOT.
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