Linear and nonlinear viscoelastic analysis of the microstructure of asphalt concretes

The paper at hand presents a methodology for analyzing the viscoelastic behavior of asphalt concretes, whose microstructure is captured through two-dimensional imaging techniques. The paper describes the viscoelastic behavior of the binder through mechanistic models fitted to rheological data obtained at different strain levels. The resulting binder stress-strain behavior is computed through a convolution integral approach and implemented into a subroutine defining material behavior in a commercially available finite element program. The use of a convolution integral approach is shown to facilitate incorporating the binder nonlinear viscoelatic behavior in the analysis of the asphalt concrete microstructure response. This is conducted by assigning the binder model constants as a function of strain level. The model is tested by comparing asphalt concrete shear modulus G^* predictions to earlier predictions obtained with a generalized piecewise linear viscoelastic model, as well as measurements obtained with a simple shear tester. The model is used to explain some of the discrepancies observed between experimentally obtained axial and shear dynamic moduli.