Abstract
By using Discrete Element simulations, we study the bulk properties of bidisperse granular mixtures. We focus on the role of the size ratio between components and show that the effective bulk modulus of a granular (base) assembly can be enhanced by up to 20% by substituting as little as 5% of its volume with smaller radius particles. Using particles of a similar size barely affects the average bulk properties of the assembly. On the other extreme, when a huge number of very small particles are included, most of them lie in the voids of the base material, acting as rattlers, leading to an overall weakening effect. In between the limits, for dense systems, an optimum size ratio that maximizes the bulk modulus of the mixture can be found. Conversely, loose systems always get weaker since more and more small particles become rattlers. Finally, we relate the mixture properties with the ‘typical’ pore size in a disordered structure as induced by the combined effect of operating volume fraction and size ratio.