Abstract
The viscometric behavior of laponite and bentonite suspensions at different concentrations in shear flow is studied. It is discovered that in the equilibrium state, a master curve of viscosity can be constructed when the applied shear stress is normalized by the respective suspension’s yield stress. The interparticle interaction controlling the yield behavior at the gel state also dominates the behavior of particles at the equilibrium flowing state. A constitutive framework is developed to describe the master curve of viscosity as a function of the shear stress normalized by the yield stress. Based on the proposed model, the effect of concentration on the viscosity of clay suspensions can be estimated via their yield stress.
Highlights
The rheological behavior of the clay suspension is complex due to strong interparticle forces between disk-shaped clay particles, including electrostatic and van der Waals forces, which is distinct from noncolloidal suspensions (Loisel et al, 2015; Mwasame et al, 2016; Vázquez-Quesada and Ellero, 2016; Chun et al, 2017; and Tanner, 2018)
At low ionic strength, the system forms a gel when the concentration reaches a critical value and becomes fluidlike when a shear stress is greater than a yield stress, τy, giving rise to the yielding behavior. τy is considered to be a very important parameter reflecting the microstructure in gel
Other approaches based on the excluded volume effects or the statistical hydrodynamic trapping of a particle by another can capture the yield stress and the elasticity of swelling clay suspensions (Michot et al, 2009; Paineau et al, 2011)
Summary
The rheological behavior of the clay suspension is complex due to strong interparticle forces between disk-shaped clay particles, including electrostatic and van der Waals forces, which is distinct from noncolloidal suspensions (Loisel et al, 2015; Mwasame et al, 2016; Vázquez-Quesada and Ellero, 2016; Chun et al, 2017; and Tanner, 2018). A number of constitutive models have been developed to predict both the transient and steady (equilibrium) rheological behavior for complicated systems, such as clay suspensions, paints, pastes, and food products, based on both phenomenological approaches (Herschel, 1924; Powell, 1995; and Phan-Thien et al, 1997) and microstructural approaches (Nguyen and Boger, 1985; Toorman, 1997; Mujumdar et al, 2002; Coussot et al, 2002; and de Souza Mendes, 2011). The steady and transient behavior of the clay suspensions in flow has been well predicted in various degrees In these models, the effect of the concentration has rarely been discussed. A rheological model is proposed based on the experimental results, in order to describe the shear thinning behavior of the clay suspension taking into account the clay concentration
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