Viscoelastic constitutive model for asphalt concrete under cyclic loading

This paper presents a mechanistic approach to uniaxial viscoelastic constitutive modeling of asphalt concrete that accounts for damage evolution under cyclic loading conditions. Schapery's elastic-viscoelastic correspondence principle is applied as a means of separately evaluating viscoelasticity and time-dependent damage growth in asphalt concrete. The time-dependent damage growth in asphalt concrete is modeled by using a damage parameter based on a generalization of microcrack growth law. Internal state variable formulation was used in developing the analytical representation of the model. Tensile uniaxial fatigue tests were performed under the controlled-strain mode to determine model parameters. Then, the resulting constitutive equation was used to predict the stress-strain behavior of the same materials under controlled-stress mode. The constitutive equation proposed in this paper satisfactorily predicts the constitutive behavior of asphalt concrete all the way up to failure under various loading conditions including different stress-strain amplitudes, monotonic versus cyclic loadings, and different modes of loading.