Concentration dependence of yield stress and dynamic moduli of kaolinite suspensions.

The concentration dependence of yield stress and dynamic moduli of kaolinite suspensions is studied. Complex electrostatic interactions between kaolinite platelets promote a more liquid-like behavior, with clay particles changing from attractive interactions to a face-face repulsive interaction as the mass fraction of clay particles increases. A yield stress model is developed based on the repulsive interaction between disk-shaped particles, which yields a good prediction of experimental observations when repulsive face-face interaction is dominant. The critical concentration when attractive interaction changes completely to face-face repulsive interaction is estimated from the theory. Four regions are identified in the variation of yield stress as a function of the concentration.