Hot-Mix Asphalt Moisture Damage as a Function of Air Void Size Distribution, Pore Pressure, and Bond Energy (05-0063)
Eyad A. Masad, Texas A&M University
Adhara Castelblanco, Texas A&M University
Bjorn Birgisson, KTH Royal Institute of Technology, Sweden

The relationship between hot mix asphalt (HMA) moisture damage, air void structure, pore pressure, and cohesive and adhesive bond energies was investigated in this study using mixes with two different aggregate types and varying gradations. Moisture damage was evaluated using parameters derived based on the principles of fracture mechanics. Air void distribution was analyzed using a probabilistic approach with the assistance of X-ray computed tomography and image analysis techniques. Statistical parameters of the air void distribution were related to permeability, which controls the ability of the water to infiltrate into and drain out of the mix. The air void distribution was found to significantly influence moisture damage. A “pessimum” air void size was found at which the moisture damage was maximum. The cohesive and adhesive bond energies of the mix were calculated based on experimental measurements of aggregate and asphalt surface energies. These measurements were used to explain the difference in moisture damage between the two mixes that were used in this study.