Mechanical Resistance due to Shearing of Partially Wet Granular Media

抄録

Mixing granular media with a given amount of liquid is an operation conducted and used intensively for the preparation of concrete. The power and time required to obtain good homogeneity of the granular paste are known to have a complex relationship with the physical properties of the particles, with the liquid and with the mixer design. In this paper some of these issues are addressed by evaluating the shear resistance of a granular paste. Using model spherical materials (glass beads) and ground and sieved minerals (calcite CaCO₃), we investigate experimentally the impact of the particle size, liquid amount and morphology of the particles.From quasi-static experiments in shear cells, different regimes of shear resistance are revealed. In dry conditions, van der Waals’ forces dominate. In wet conditions, a capillary or consolidation regime where shear resistance is dominated by capillary forces is strongly impacted by the morphology of the particles and by the formation of texture. These regimes are qualitatively observed in a bowl mixer for which the variation of the current intensity correlates with the shear resistance observed in quasi-static experiments.