Rheological studies on the flow behavior of two-phase solid-liquid materials

Abstract

Fresh concrete as well as mortar can be considered as a two-phase material with solid particles dispersing in non-Newtonian fluid. In this study, rheological models were developed to predict the flow behavior of cement-based two-phase materials. The models include four different aspects: aggregate particles direct shear stress, fresh cement paste yield stress, fresh mortar yield stress and shear stress. Firstly, mathematical approach to model the direct shear of coarse granular material was performed in order to study the relationship between the bulk internal friction angle of granular materials and the friction coefficient of raw material of granular materials, the former can be measured directly by different methods, however, the later cannot. Threedimension probabilistic and mechanical two-particle contact models were developed to calculate both the shear stress generated on shear plane when granular material is under direct shear and volume change due to shear. The models show that the friction angle of coarse granular materials is dependent on surface properties of granular material, and independent on the size of and size distribution of granular material. Direct shear tests on different type of particles were performed using standard direct shear box and a modified large size direct shear box. For different kind of granular materials, the peak friction angles showed good consistence with previous experimental results and proved that the present models are reasonable and experimentally correct.