Fatigue damage growth and healing of asphalt concrete are studiedin this paper using laboratory and field experiments. The fieldstudy was performed using the stress wave technique on asphaltpavement sections with varying degrees of damage. The elasticmodulus of an asphalt concrete layer is calculated from the stresswave data using the dispersion analysis based on Short KernelMethod. The laboratory study employs two fundamentally differentapproaches to modeling the mixture fatigue behavior; continuumapproach and micromechanical approach.

The continuum approach applies the elastic-viscoelastic correspondenceprinciple to eliminate the time-dependence from the hystereticbehavior of asphalt concrete under cyclic loading. Pseudo stiffness,stiffness after the application of the elastic-viscoelastic correspondenceprinciple, decreases following a characteristic S-shape curvedue to the fatigue damage growth when plotted against number ofloading cycles. This curve is vertically shifted when rest periodsare introduced, resulting in a longer fatigue life. The same trendis observed from the field study between the elastic modulus andthe number of loading cycles.

Work potential theory, a continuum damage theory based on thermodynamicsof irreversible process, is then applied to the laboratory datato model the changes in pseudo stiffness due to fatigue damagegrowth and microdamage healing. The resulting model is found tobe mode-of-loading independent and capable of predicting the changesin stress-strain behavior under compound loading histories withmulti-level loading and varying durations of rest. A validationstudy is performed on the fatigue performance prediction modelusing the data obtained from uniaxial fatigue testing of AAD andAAM mixtures under constant stress/strain amplitude cyclic loadinghistories with and without rest periods.

Finally, a micromechanical approach is presented which describesa fracture process as a balance between the energy imparted tothe system and the energy taken up by the newly created cracksurfaces. Different microdamage healing behavior of AAD and AAMmixtures described by the coefficients in the continuum damagemodel is explained by the difference in micromechanical propertiesbetween the two binders, such as total cohesive surface energyand different proportions of the Lifschitz-Van der Waals and theacid-base components in the surface energy.