Viscoelasto-plastic Modelization of the Stone Mastic Asphalt Creep Behaviour

This paper introduces and discusses a viscoelasto-plastic constitutive model for the characterization of the creep behavior of asphalt concretes at high temperature. The correspondent uniaxial model was composed by a plastic element in series with a viscoelastic component, the latter given by an elastic spring in parallel with three Maxwell elements. Three different hardening laws, namely isotropic, kinematic and mixed hardening, have been implemented in the constitutive equations, in order to compare the different response in the prediction of the creep permanent deformation. A Stone Mastic Asphalt (SMA) has been tested under uniaxial creep-recovery tests at 40°C, at different stress and loading times; the creep-recovery data have been used in order to calibrate and then validate the constitutive model developed. The permanent deformation data predicted by the model resulted consistent with the experimental creep-recovery data, depending on the hardening law considered, so demonstrating the relevance of an appropriate modelling of the plastic behavior, in the analysis of the creep response of bituminous materials.