(79e) Energy Distribution in the Squeezing of Particles in Concentrated Suspension

In the present work, the squeeze flow geometry is used to investigate the properties of concentred suspensions. The suspensions consist on hard glass spherical particles dispersed in a viscoplastic fluid. With such a material, following the solid volume fraction, the material rheological behaviour ranges from purely viscoplastic fluid to granular media. Thus, the shear rate has a main effect on the rheological behaviour because, at low shear rate, drainage effect through the granular squeleton produces. Moreover, materials with high solid volum fraction are generally submitted to local consolidation. During the squeezing action, the material structure suddenly evolves with energy losses due to particle displacement. The goal of our study is to identify the effect of these energy losses on the flow properties of suspensions. Flow can appear like a succession of quasi-steady and transient states. These modifications may occur, as example, during extrusion of cement composites pastes. During squeeze test, the sample height decreasing changes the distance between particles and modify the energy distribution in the squeezed volume. The proposed study consist on a energy approach based on the analysis of the global squeeze force and sample height with time. The squeeze force is decomposed in a combination of an average force component and a fluctuating one. This local fluctuating component is first investigated as a function of solid volum fraction and compression velocity. Results show the evolution of the energy distribution during compression and permit to detect the flow regime modification. Finally, the relationship between the fluctuating force component and the suspensions behaviour is studied.