Concentration Dependence of Yield Stress and Dynamic Moduli of Kaolinite Suspensions

Abstract

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.

Effect of temperature on rheological behavior of kaolinite and bentonite suspensions

“…2 shows the yield stress deduced from the shear-rate curves. Clearly, we find that the yield stress of clay suspensions increases with increasing mass fraction, c, and temperature, T. y becomes more sensitive to the concentration at higher T. As the yield stress is related to the electrostatic interactions between clay particles [15,10,11], the temperature-dependence behavior of yield stress is proposed to be caused by the change of electrostatic potential of clay particles with temperature. García-García et al [16] find the repulsive energy potential of two neighboring particles increases with increasing T, which would affect the yield stress of the clay suspension.…”

“…Take kaolinite suspensions for example, when the applied shear stress exceeds a critical stress, the shear rate increases sharply by several orders of magnitudes, while below this critical stress, the shear rate is negligibly small and reflects mainly a solid-like behavior. This critical stress may be defined as yield stress, y , as was done in our previous work [15]. From Fig.…”

“…3(b), the phase angle, ı, defined as tan ı = G /G is found to increase with increasing clay concentration at 25 • C, indicating a more liquid-like property. In our previous study, we consider that the increasing of ı should be accounted for the change of gel structure with increasing mass fraction of kaolinite clay [15]. At low concentrations (e.g., c = 0.1), the card-house structure resulting from a face-edge attractive electrostatic interaction is dominant, while at higher concentrations (c ≥ 0.22), due to the packing effect, the card-house structure is replaced completely by a face-face structure which is stabilized by the repulsive electrostatic interaction between clay particles.…”

“…As a result, the yield stress is mainly determined by the electrostatic double-layer forces between particles [10][11][12][13][14]. For kaolinite suspensions, it is found that the yield stress origins from the edge-to-face electrostatic attractive interaction between particles at a low concentration, while the interaction changes to the face-to-face electrostatic repulsive interaction with increasing concentration of clay [15]. The effect of temperature on the rheological properties has rarely been studied.…”

“…The temperature behavior is related to the changing of repulsive electrostatic potential based on our previous study [15].…”