This research project utilized laboratory evaluations to study effects of freeze-thaw cycling on the tensile strength of eight Hot Mix Asphalt mixtures and to determine if the Georgia Loaded Wheel Tester could be utilized to measure moisture susceptibility of Hot Mix Asphalt mixtures. The evaluation involved eight Hot Mix Asphalt mixtures from combinations of two aggregate types and four asphalt-additive-aging possibilities. Laboratory testing was accomplished in the first phase with the production of 2.5 by 4 inch cores that were freeze-thaw cycled and tested for their indirect tensile strength following Wyoming modified AASHTO T283. The second phase was accomplished using 3 by 6 inch cores that were conditioned and tested for rutting using the Georgia Loaded Wheel Tester. Finally, a statistical analysis was performed to determine if performance of the various mixtures was significantly different in groups of asphalt types and to determine if the Georgia Loaded Wheel Tester was a viable measurement tool for moisture susceptibility.

This synthesis will be of interest to pavement designers, construction engineers, maintenance engineers, and others interested in avoiding or limiting moisture damage in asphalt concrete. Information is provided on physical and chemical explanations for moisture damage in asphalt concrete, along with a discussion of current practices and test methods for determining or reducing the susceptibility of various asphalt concrete components and mixtures to such damage. Moisture damage in asphalt concrete is a nationwide problem which often necessitates premature replacement of highway pavement surfaces. This report of the Transportation Research Board describes the underlying physical and chemical phenomena responsible for such damage. Current test methods used to determine the susceptibility of asphalt concretes, or their constituents, to moisture damage are described and evaluated. Additionally, current practices for minimizing the potential for moisture damage are examined.

"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's description