Thermodynamic framework for the constitutive modeling of asphalt concrete: Theory and applications

The response of an asphalt concrete pavement to external loading depends on its internal structure. Using a recent framework that associates different natural configurations (for example, stress-free configurations) with distinct internal structures of the body, we model asphalt concrete. We assume asphalt concrete to be a mixture of, an aggregate matrix and an asphalt mortar matrix with evolving natural configurations. The evolution of the natural configuration is determined using a thermodynamic criterion, namely, the maximization of the rate of dissipation. Appropriate choices for the Helmholtz potential, the rate of dissipation and the other thermodynamic criteria are assumed to describe how energy is stored, the manner of the rate of dissipation, etc. As an example, we choose a specific form for the Helmholtz potential and the rate of dissipation function that leads to a generalized "upper convected Burgers's model," its linearized version being the viscoelastic model that is usually used for modeling asphalt concrete. This model is just an example of how a class of thermodynamically consistent models can be generated to describe the nonlinear behavior of materials such as asphalt concrete. We model the uniaxial compressive and tensile creep of asphalt concrete for two different types of specimens,and test methods. We provide details of the numerical scheme we use to solve the initial value problem and we compare the experimental data of Monismith and Secor in 1962 with predictions of the model.