Date of Award
8-2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil Engineering
Committee Chair/Advisor
Dr. Bradley J. Putman
Committee Member
Dr. Prasad Rao Rangaraju
Committee Member
Dr. Amir Poursaee
Committee Member
Dr. Whitney Huang
Abstract
The objective of this study was to characterize the variability of dynamic modulus of asphalt mixes in South Carolina on the basis of geometry and anisotropy. 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 seven different contractors each having a different aggregate source and 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. One-way ANOVA test was conducted on the control specimen to find the variability of dynamic modulus between mix types and contractor. The results showed that there were 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 130℉) and lower frequencies, there was less variability between the mixes for a given contractor. The feasibility of having small-scale specimen was analyzed and the results show that reducing the specimen size from 100 mm x 150 mm to 38 mm to 110 mm has direct effect on dynamic modulus and the small-scale specimen had reduction in dynamic modulus as well. The ratio of small-scale to the control specimen ranged from 0.81 to 1.23 with an average of 0.96. The feasibility of having specimen cored horizontally was studied so that determining the dynamic modulus of field cores are possible where each individual layer could be extracted from the composite specimen to study the pavement performance. The horizontally cored specimen exhibited an opposite trend to the vertically cored specimen, where there was an increase in dynamic modulus. The horizontally cored specimen exhibited higher dynamic modulus than the control specimen. The ratio of small-scale horizontal to control specimen ranged from 0.84 to 1.32 with an average of 1.06. The mastercurves generated for control and small-scale samples indicated that the horizontally cored specimen was in alignment with the control specimen than the vertically cored specimen. It also showed that the small-scale specimen had little to no variability in dynamic modulus with the control specimen at lower temperatures. There was high variability at high temperatures irrespective of mic type and contractor. The pavement performance using the PavementME indicated that horizontally cored small-scale specimen was highly resistant to AC layer deformation and prone to top-down cracking. But the opposite trend was observed in the vertically cored small-scale specimen where it was prone to rutting and resistant to cracking. This is solely because the horizontal specimen had higher dynamic modulus while the vertically cored specimen had lower dynamic modulus. The dynamic modulus data on field cores cored horizontally indicates the feasibility of testing the field specimen with a reduced dimension. Banks SMA had similar dynamic modulus for both field cores and plant mix-lab compacted cores. The lab/field performance was close to 1 for all the distresses except top-down cracking which was found to be 0.85. The above result was an indication that the mixes produced at the plant and compacted at the lab was an ideal representation of actual pavement in the field.
Recommended Citation
Nagarajan, Srinivasan, "Influence of Specimen Geometry and Anisotropy on Dynamic Modulus of Asphalt Mixes in South Carolina" (2022). All Dissertations. 3136.
https://tigerprints.clemson.edu/all_dissertations/3136
Author ORCID Identifier
0000-0002-3382-2858