Modelling the nonlinear viscoelastic response of asphalt binders

In a recent article, Narayan et al. [Narayan, S.P.A., et al., 2012b. Nonlinear viscoelastic response of asphalt binders: experimental study of relaxation of torque and normal force in torsion. Mechanics Research Communications, 43, 66–74] recorded both torque and normal force in torsional relaxation experiments on asphalt binders. The data are three-dimensional and thus, require interpretation using three-dimensional constitutive relations. In this article, we develop such a three-dimensional nonlinear viscoelastic model for asphalt binder. The predictions of the model fit the experimental data reasonably well. While there are already some three-dimensional constitutive relations available in the literature for asphalt binders which can describe the normal forces that are developed during torsion, they do not capture the relaxation behaviour presented by Narayan et al. (2012b). This new model, however, captures most of the key features of the experimental data including the development of normal forces in torsion and the relaxation behaviour. In this respect, the new model performs considerably better than the existing models.