Nanoscale modeling of the mechanical properties of asphalt and aggregate

Asphalt binder and mineral aggregates constitute the building blocks of asphalt concrete as pavement materials. An important trait of these materials is that they display highly characteristic hierarchical structures across multiple scales from nano to macro. Asphalt and aggregates are intriguing examples of materials that balance multiple tasks, representing some of the coarse/fine frame and stick solutions that integrate structure/function. This paper presents nanoscale modeling to investigate the mechanical properties of asphalt/mineral materials to investigate structure-property relations. The atomistic simulation provides a powerful approach in studying mechanical properties of asphalt concrete materials. The molecular origin of mechanical processes of two minerals and two asphalt mix models are demonstrated in this paper. Elastic constants of bulk quartz and calcite, as well as thermodynamic quantities of two asphalt molecular structures are all calculated. The simulation results indicate that the characteristics of bitumen are determined by both the constitution (chemical composition) and the structure (physical arrangement) of the molecules in the bitumen. Changes to the constitution, structure or both will result in a change to the thermodynamic and mechanical properties. In addition, viscosity and cohesive energy density of asphalt molecular models are both temperature dependent quantities. Furthermore, the highly anisotropic elastic properties of mineral structure appear at atomic scale. The elastic constants from atomistic simulation have both positive and negative values, as well as the non-diagonal components of mineral crystals can be non-zero at nanoscale. These mechanical properties are in correspondence with the two mineral crystals structures.