A theoretical-experimental visco-elastic-plastic analysis of Mastic Asphalt

This report introduces a generalised visco-elastic-plastic constitutive model for the characterization of stress-strain behaviour in asphalts (bituminous mixtures), with particular reference to the problem of permanent deformation accumulation. With the introduction of the function of density of Helmholtz free energy, for the description of the energy status of visco-elastic-plastic material, and with the support of appropriate internal variables, it has been possible to express a law of plastic flow in mechanically rigorous terms, which can reliably quantify permanent deformations. The formulation of the constitutive relationship has been developed in such a way as to verify “a priori” the universal dissipation principle, expressed by the Clausius-Duhem dissipative inequality, and bound to the thermodynamic constraints that the system has to satisfy. The model has been calibrated and validated on the basis of the deformation behaviour of a particular Mastic Asphalt mix, through a specifically developed experimental-numerical procedure.