Modeling the DSR complex shear modulus of asphalt binder using 3D discrete element approach

The mechanical performance of an asphalt mixture is largely dependent on the material properties of its components and the way they are reciprocally interacting. Asphalt binder plays a very significant role because it displays a time and temperature dependent behavior that is characteristic of a viscoelastic material. An understanding of the contacts mechanisms of the system through a 3D micromechanical model provides insight into the macroscale material behavior, and guides its design and performance prediction. Based on such considerations, a micromechanical based three-dimensional discrete element approach was used in order to capture the time-dependent behavior usually studied with the Dynamic Shear Rheometer analysis. The results, obtained comparing the numerical simulation of a frequency sweep test with a laboratory one, show that the adopted approach is found to be successful in predicting, both quantitatively and qualitatively, the complex modulus and the phase angle of the studied polymer modified bitumen, over a wide range of temperatures and frequencies. In addition the microstructural analysis has permitted to evaluate the internal forces configuration induced by shear stress in the specimen.