Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
R. Christopher Williams
Moisture damage in hot mix asphalt (HMA) pavements has been extensively documented since the late 1970's. The current test method for detecting moisture susceptibility in HMA is American Association of State Highway and Transportation Officials (AASHTO) T283. Inclusion of this test method in Superpave did not consider the change in specimen diameter size from 100mm to 150mm nor corresponding heights, method of compaction, nor is AASHTO T283 a performance test to accompany the mix design procedure;A new test procedure to evaluate the moisture susceptibility of HMA was developed in this dissertation. In addition, two sensitivity studies were undertaken: (1) Using AASHTO T283 to consider the number of freeze-thaw cycles, diameter size, and compaction method and (2) Evaluation of test temperature, conditioning, and dynamic modulus and flow number tests. This dissertation develops a moisture susceptibility procedure which utilizes the dynamic loading of saturated and unconditioned sets of specimens and compares the two sets of specimens. The Witzcak model is also analyzed to see how well the model predicts dynamic modulus on conditioned and unconditioned specimens. The major findings of this research are: (1) Three freeze-thaw cycles for conditioning is satisfactory when using Superpave compacted specimens. (2) To maintain the same probability level as attained with a TSR value for 80% for 100mm diameter Marshall compacted specimens, a TSR value of 87 and 85% should be used with 150mm and 100mm diameter Superpave compacted specimens, respectively. (3) It was determined that the effective test temperature for rutting would be used for dynamic modulus testing of moisture conditioned specimens and would follow the conditioning procedure outlined in AASHTO T283. (4) The new test procedure uses a retained dynamic modulus of 60% of conditioned specimens to unconditioned specimens for all frequencies. (5) A statistical analysis was performed: gradation, NMAS, traffic, polymer modification, aggregate type, permeability, asphalt content, FAA, RAP, and frequency for dynamic modulus testing. The factors affecting AASHTO T283 are polymer modification, aggregate type, permeability, and RAP. The factors affecting dynamic modulus are mix type, polymer modification, aggregate type, permeability, RAP, and frequency. (6) Local calibration is needed for the Witczak model.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Jason Paul Bausan
Bausano, Jason Paul, "Development of a new test procedure to evaluate the moisture susceptibility of hot mix asphalt " (2006). Retrospective Theses and Dissertations. 3076.