Discrete Element Simulation of Bending Beam Rheometer Tests for Asphalt Binder

Abstract

This study presents a discrete element modeling approach to bending beam rheometer (BBR) tests for control and nanomaterial modified asphalt binders. In the discrete element model, a linear elastic contact model was used to simulate force displacement relations among adjacent elements, while a slip model and two bonding models were used to simulate the strength properties at each contact. The two bonding models include the contact bond model and parallel bond model, which were utilized simultaneously. In order to compute contributions of the two bonding models, a coefficient of α was introduced. A compressive study found that discrete element simulation results were acceptable when α was close to 1.0. Since asphalt materials exhibit time dependent behaviors and cannot be directly simulated with an elastic model, the time domain was represented by a few key time points that were simulated individually to account for the time dependency of asphalt materials. In order to obtain inputs for the discrete element model, BBR testing results of control and nanomaterial modified asphalt binder were fitted with the five-parameter Generalized Maxwell model, which represents the laboratory testing data well. A careful analysis of the discrete element simulation results indicates that 1) the discrete element model in this study can simulate a BBR test of asphalt binder, and 2) the stress and displacement distributions within the beam model can be virtualized and demonstrated.