Experimental Evaluation of a Simple Contact Model Containing Two Elastic Particles Bonded by a Thin Layer of Viscoelastic Binder

Abstract

This paper presents an experimental study on the aggregate contact behavior in asphalt mixture. As a three-phase material composed of aggregates, asphalt binder, and air voids, asphalt mixture is considered as a viscoelastic material at a low stress level. The behavior of the mixture depends largely on the interaction among different components. A contact model between two aggregates is very important for understanding the deformation mechanism of the mixture. In this study, a contact model between two aggregates was reviewed in details. A closed-form time-dependent relationship between the contact forces and the relative particle/binder movements was derived. An experimental test was designed to evaluate the model which contains two elastic particles bonded by a thin layer of asphalt binder. The displacement and resistant force of the aggregate-binder system under uniaxial compression loading were documented using a cabinet X-ray tomography system. The effectiveness of the model was evaluated by comparing the experimental results with the theoretical model predictions. It was found that the model performs better when the thickness of binder is thinner. Polynomial regression equations are more suitable to fit the model-predicted results with experimental results. Selection of the model parameters is also critical to the performance of the model. The effect of the binder film thickness on the aggregate-aggregate contact was also discussed with different binder layer thicknesses. It was found that the stiffness of the aggregate-binder-aggregate system increases as the bonding layer gets thinner, which indicates that optimum asphalt content is very important to the mix design of asphalt concrete.