Particulate Systems with Viscous and Viscoelastic Cement: From Contact Laws to Macroscopic Behavior

The overall objective of the proposed research was to provide a quantitative description of the microstructural, as well as macroscopic mechanical behavior of particulate materials with viscous and viscoelastic intergranular cement. By cement, a material is meant which fills the space between two or more particles at their contacts. The volumetric content of cement in the pore space of an aggregate may vary from zero to 100%. This objective was achieved by deriving microstructural contact laws for the combination of two elastic spherical grains with viscous cement. A simple and accurate viscoelastic approximation (Cole-Cole model) was found for the rigorous micromechanical solution. The contact law thus obtained was used to calculate the effective elastic moduli of a granular aggregate with viscous cement at a varying frequency of oscillations. The theoretical results were verified by experiments conducted on a pack of glass beads with viscous epoxy cement. Our second achievement was the extension of an exact solution for the elastic moduli of a cemented grain pack at a low cement content to a solution for the case where cement occupies the entire pore space or a large portion of it. The main relevance to the Air Force mission is through a quantitative description of cemented geomaterials such as asphalt cement. The results have been used at the Wright Laboratory to model asphalt concrete's behavior.