Viscoelastoplastic Continuum Damage Model Application to Thermal Cracking of Asphalt Concrete

A viscoelastoplastic continuum damage (VEPCD) model has recently been developed and validated under the auspices of the National Cooperative Highway Research Program 9-19 project, entitled “Advanced Mixture Characterization for Superpave Support and Performance Models Management.” The VEPCD model is able to characterize the viscoelastic and viscoplastic responses of asphalt concrete (AC) in addition to microcracking. The primary objective of this paper is to validate the model under thermal loading conditions that are distinctively different from the mechanical loading conditions used in model development and calibration. Viscoplastic (VP) behavior is a typical response in AC at high temperatures; however, based on the t-T superposition principle, it is the slow strain rate observed in thermal cracking that triggers the VP response. Measured responses and fracture parameters from thermal strain restrained specimen tensile (TSRST) strength tests were compared with those predicted using the VEPCD model, the viscoelastic continuum damage model, and the linear viscoelastic model. The comparison confirmed: (1) the ability of the VEPCD model to accurately characterize the tensile behavior of asphalt concrete under thermally induced loading; and (2) a decrease in accuracy as the complexity of the model decreases.