Philip F. Low, 1992. "Interparticle Forces in Clay Suspensions: Flocculation, Viscous Flow and Swelling", Clay-Water Interface and its Rheological Implications, P. F. Low, J. K. Mitchell, G. Sposito, H. van Olphen, N. Güven, R. M. Pollastro
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Forces between clay particles influence many industrial, geological, geotechnical and pedological processes. They include the van der Waals' force, the Coulomb force, the Born force, the double-layer force and the hydration or structural force. General discussions of these forces have been published by Verwey and Overbeek (1948), Derjaguin et al. (1987), Israelachvili (1974), Ninham (1981, 1985) and, elsewhere in this volume, by Güven. Therefore, the author will not discuss them further but will focus his attention on the roles they play in the processes of flocculation, viscous flow and swelling. Swelling will get the most emphasis because of the author's special interest in it. In particular, an attempt will be made to assess the relative contributions of double-layer and hydration forces to the swelling pressure and, thereby, facilitate the resolution of a long-standing controversy.
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Rheology is the science of the flow of fluids and deformation of solids. Of special interest to the clay scientist are the flow behavior and stability of clay suspensions, and the time-dependent deformation of clays in a solid or semi-solid state. The physical state of a clay may change with increasing water content; from a solid, to a semi-rigid plastic, then to a gel, and finally to a suspension. In each state, the main factors determining the rheological behavior of the system are related to: (a) the molecular configuration and dynamics of the clay-water interface, and (b) the nature of the particle interactions at this interface. The hydration of the ions and the clay surfaces plays a special role in clay rheology because flow and deformation directly involve molecular movements along the clay-water interface.