CHARACTERIZATION OF ASPHALT CONCRETE IN UNIAXIAL TENSION USING A VISCOELASTOPLASTIC CONTINUUM DAMAGE MODEL (WITH DISCUSSION)

The objective of the research presented in this paper is to develop an accurate and advanced material characterization procedure to be incorporated in the Superpave performance models system. The procedure includes the theoretical models and its supporting experimental testing protocols necessary for predicting responses of asphalt mixtures subjected to uniaxial tension loading. The model encompasses the elastic, viscoelastic, plastic and viscoplastic components of asphalt concrete behavior. Some of the major factors affecting asphalt concrete response, such as rate of loading, loading time, stress/strain amplitude, temperature, and damage, are addressed. The modeling strategy is based on developing separate models for strain components and then integrating those models to form a viscoelastoplastic continuum damage (VEPCD) model. The developed model accurately predicts responses up to localization when microcracks start to coalesce and grow. After that, fracture process zone strains detected using digital image correlation are used to extend the model's ability in predicting responses in the post-localization stage. However, once major macrocracks develop and propagate, the currently developed model ceases to predict responses accurately. At that state, fracture mechanics needs to be integrated with the current continuum damage-based model to predict the response.