Viscoplasticity Modeling of Asphalt Concrete Behavior

A constitutive model based on an extended form of the Schapery continuum damage formulation is currently being evaluated and developed as a comprehensive material model for asphalt concrete. This model considers the viscoelastic, damage, and viscoplastic components of asphalt concrete behavior over the full range conditions of interest for the mechanistic prediction of flexible pavement distresses. The focus of the present paper is limited to the viscoplastic response component at intermediate and high temperatures. The results confirm earlier findings that asphalt concrete in compression is a thermorheologically simple material well into the large strain viscoplastic regime at elevated temperature. The study demonstrates that the proposed viscoplastic model component provides a good representation of the viscoplastic response of asphalt concrete in uniaxial unconfined compression. Given the validity of time-temperature superposition for viscoplastic response, the viscoplastic material parameters can be calibrated from a limited number of uniform time and uniform load creep and recovery tests. Typical viscoplastic material parameters are derived for a representative asphalt concrete mixture.