A VISCOELASTIC CONTINUUM DAMAGE MODEL AND ITS APPLICATION TO UNIAXIALBEHAVIOR OF ASPHALT CONCRETE

An existing viscoelastic constitutive model which accounts for the eff ects of rate-dependent damage growth is described and applied successf ully to characterize the uniaxial stress, constant strain rate behavio r of asphalt concrete. The special case of an elastic continuum damage model with multiaxial loading, which is based upon thermodynamics of irreversible processes with internal state variables, is first reviewe d and then it is shown how this model has been extended to a correspon ding viscoelastic damage model through the use of an elastic-viscoelas tic correspondence principle. The general mathematical model is next s pecialized to uniaxial loading. A rate-type evolution law, similar in form to a crack growth law for a viscoelastic medium, is adopted for d escribing the damage growth within the body. Results from laboratory t ests of uniaxial specimens under axial tension at different strain rat es are then shown to be consistent with the theory. The discussion of data analysis describes the specific procedure used here to obtain the material parameters in the constitutive model for uniaxial loading an d how the method may be generalized for multiaxial loading.