Two-Stage Viscoelastic-Viscoplastic Damage Constitutive Model of Asphalt Mixtures

A two-stage viscoelastic-viscoplastic damage constitutive model is developed for describing different mechanical deformation response of asphalt mixtures under various loading conditions. The model decomposes total strain into viscoelastic and viscoplastic components with damage considered. The model is calibrated using the creep-recovery test for viscoelastic parameters and using the static triaxial creep test for viscoplastic parameters, respectively. The calibrated constitutive model is then validated using triaxial constant strain rate compression tests. The calculated volumetric deformation exhibits initial contraction caused by viscoelastic component of the model, followed by dilation caused by the viscoplastic damage component, which is consistent with the experimental phenomena. Results show that the model can reasonably represent the three-stage deformation of creep test as well as the hardening and softening stages of constant strain rate compression test.