Temperature-Dependent Viscoelastic Model for Asphalt–Concrete Implemented within a Novel Nonlocal Damage Framework

AbstractA viscoelastic constitutive model for an asphalt–concrete (AC) material that accounts for temperature and material degradation effects is proposed. The model is implemented within a finite-element framework and consists of a new nonlocal damage regularization approach that is based on a nondimensional equivalent stress measure. The viscoelastic model is introduced as a generalized Maxwell model with the shear modulus described in terms of Prony series. Damage behavior is described in rate form with an anisotropic damage accumulation law for tension, compression, and shear loadings. Prediction of the AC response is obtained by solving the nonlinear system, which includes an equilibrium equation that is coupled to a nonlocal damage equation. The latter introduces a length scale in the problem that renders the damage results mesh-independent. The system is solved implicitly until convergence using a robust staggered scheme. A rigorous material calibration is carried out for both viscoelastic and damage material parameters using optimization techniques. The proposed material model is validated by comparison to published experimental tests conducted on a range of temperatures from −20°C to 0°C. In particular, an Arrhenius-type relation is introduced to describe the dependence of material damage on temperature. Good agreement between predicted and experimental results shows that the proposed model is suitable for describing the thermoviscoelastic damage behavior of common AC.