Fluidities of Thixotropic Gels: Bentonite Suspensions

Abstract

Flow measurements on bentonite suspensions, showing both the property of thixotropy and of fluidity variable with shearing stress, were performed in capillary tubes, brass pipes, and a rotary consistometer of special design. The latter instrument was used to show that the structure of such gels must be broken down or built up until an equilibrium state of flow is attained to obtain reproducible measurements. No slippage at the walls was found in non-plug flow. Turbulent flow of bentonite suspensions was investigated in one-half and one-inch pipes. It is demonstrated that these materials behave as any viscous liquid, in the turbulent region, and that the volume of flow at any pressure gradient may be assumed to be the same as for water, without great error. The importance of obtaining equilibrium flow conditions for fluidity measurements is stressed.