Date of Award
Master of Science (MS)
Dr. Bradley J Putman
Dr. Prasad Rao Rangaraju
Dr. Kalyan Piratla
The objective of this study was to characterize the variability of dynamic modulus of asphalt mixes in South Carolina. High priority mixes Surface Type B, and C; Intermediate Type B and C and Base Type A from three different days of production were collected from two different contractors each having a different aggregate source. The dynamic modulus was measured using the Asphalt Mixture Performance Tester (AMPT) at temperatures of 40, 70, 100 and 130℉ (4.4, 21.1, 37.8, and 54.4℃) and at frequencies of 25, 10, 5, 1, 0.5, and 0.1 Hz. The dynamic modulus from the AMPT is then used to determine the fitted dynamic modulus value using the Hirsch prediction model. The principle of time temperature superposition was used to fit the obtained dynamic modulus values from the AMPT onto a master curve which yielded the fitted dynamic modulus that serves as an input variable in the PavementME.
One-way ANOVA test was conducted on the dynamic modulus values from the AMPT to find its variability between production day, mix types and contractor. The results showed that there were significant differences in production day between the contractors. Based on variability in the mix type results, as expected, both contractors had similarities in their Intermediate mixes and Surface mixes. When both the contractors were compared on the mix type variability, Base A and both the Surface mixes had a trend of being similar at low temperatures and both the Intermediate mixes were significantly different between the contractors.
Similar one-way ANOVA was carried on the fitted dynamic modulus values and checked for variability in mix types and contractor. The results indicated no significant differences between the contractors for Intermediate mixes and Surface C and some, but little, variability in Base A and Surface B mix. Also, at higher temperatures (70, 100 and 130oF) and lower frequencies, there was less variability between the mixes for a given contractor. At lower temperature, there were differences between Base and Surface B mix type for Contractor 2 but not in Contractor 1.
The mix properties were used to analyze the influence of the results in the MEPDG and the results indicated that pavements made with materials from Contractor 1 performed better than Contractor 2 for same pavement section due to higher dynamic modulus at lower temperature. Additionally, there were no significant differences between surface mixes and intermediate mixes for a particular contractor source. Sensitivity analysis carried out on individual mix types from both contractors indicated similar trend in distress prediction. But the distress values for Contractor 1 was found to be lower than that of Contractor 2. This result was complimented by the better performance of Contractor 1 as seen in the other sensitivity analysis.
Nagarajan, Srinivasan, "Investigation of the Variability of Asphalt Dynamic Modulus in South Carolina and Its Influence in the MEPDG" (2019). All Theses. 3234.