A serial two-stage viscoelastic–viscoplastic constitutive model with thermodynamical consistency for characterizing time-dependent deformation behavior of asphalt concrete mixtures

A serial two-stage viscoelastic–viscoplastic constitutive model is developed using internal variables theory and orthogonality principle of thermodynamics for modeling time-dependent behavior of asphalt concrete mixtures. In one stage when the actual stress is lower than the yield stress, the constitutive model only exhibit viscoelastic component, while in another stage when the actual stress exceeds the yield stress, the constitutive model exhibit both viscoelastic and viscoplastic components. Model parameters of viscoelastic component are estimated using data obtained from dynamic modulus test, whereas model parameters of viscoplastic component are consecutively estimated from creep test, assuming a known viscoelastic component.