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 (stress-free) configurations with distinct internal structures of the body, asphalt concrete is modeled. The authors assumed asphalt concrete to be a mixture of aggregate matrix and 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 and the manner of the rate of dissipation. As an example, a specific form for the Helmholtz potential and the rate of dissipation function that leads to a generalized "upper convected Burgers's model" were chosen, its linearized version being the viscoelastic model that is usually used for modeling asphalt concrete. This model is just one example of how a class of thermodynamically consistent models can be generated to describe the nonlinear behavior of materials such as asphalt concrete. The uniaxial compressive and tensile creep of asphalt concrete for 2 different types of specimens and test methods are modeled. Details are provided of the numerical scheme used to solve the initial value problem, and the experimental data of Monismith and Secor (1962) is compared with predictions of the model.