Rheological Behavior of Artificial Flocculated Clay/Guar-Gum Suspensions

Abstract

In this paper, artificial flocs, similar to the ones that are found in a recently deposited cohesive seabed, were prepared using Ca-montmorillonite and kaolinite (two of the most abundant clay minerals), guar gum (a polysaccharide closely resembling natural marine organic matter), and artificial sea water, in order to investigate the effect of the composition on their rheological response. Shear rate effects on viscosity of these suspensions were also systematically addressed. These effects typically have a strong influence on the overall rheological response of materials incorporating any polymeric substance. It was found that the addition of guar gum, even as little as 5% relative to the clay content, increases the viscosity of the floc suspensions significantly. The higher the guar-gum and clay content, the greater is the viscosity of the floc suspensions, within the guar-gum loading range investigated in this study. The floc suspensions with higher solid content were found to exhibit a slight shear thinning behavior, apparently due to the breakdown of the floc structure under high shear stress. This behavior is more pronounced in montmorillonite floc suspensions than in the kaolinite suspensions due to the differences in the clay mineral surface charge properties and surface-to-mass ratios. We explore different rheological models in their applicability to describing the observed viscous response and conclude that a cross-type formulation may be most appropriate.