# Mechanism controlling the volume change behavior of kaolinite

Rao, SH and Sridharan, Asuri (1985) Mechanism controlling the volume change behavior of kaolinite. In: Clays and Clay Minerals, 33 (4). pp. 323-328.

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## Abstract

The possible physical and chemical forces controlling the volume change behavior of kaolinite [1318-74-7] were ascertained from the sediment volume of kaolinite in various solvents under no external load condition and from conventional oedometer measurements of kaolinite in several pore fluids. The minimum sediment volume of $14.5 cm^3/10 g$ clay occupied by kaolinite in water where repulsive (R) forces were dominant indicated that the R contribution was insignificant for kaolinite. The maximum sediment volume of $25.0 cm^3/10 g$ clay in $C_6H_6$, where coulombic attraction forces were significant, suggested that electrostatic attraction between silicate sheets and midplane cations and van der Waals forces were not appreciable for kaolinite. The positive edge-negative face bonding of kaolinite particles in $C_6H_6$ was unlikely. The $3688 cm^{-1}$ band in the IR spectrum of a kaolinite-dimethylamine sample decreased by $10 cm^{-1}$ on H-bond formation of the solvent molecule with the exposed structural hydroxyls of the octahedral sheet. The adsorbed solvent molecules likely H-bonded with an adjacent clay particle as indicated by the decrease in sediment volume with increase in dipole moment of the solvent molecule. In the oedometer tests with various pore fluids, a high void ratio of approximate 1.3 was obtained for kaolinite in n-heptane, and hexane (\mu \simeq 0) at an external pressure of $1 kg/cm^2$ probably because the weakly bonded kaolinite particles were randomly oriented. At the corresponding applied pressure, a lower void ratio of 0.88 resulted in water (\mu = 1.84) where the stronger H-bond between flat layer surfaces of adjacent particles favored a parallel orientation of clay particles. The volume change behavior was essentially controlled by frictional forces and clay fabric. In nonpolar solvents the random arrangement of kaolinite particles and the frictional forces mobilized a high shear resistance on the application of a consolidation pressure, resulting in a lower compressibility. In a solvent with high dipole moment the parallel array of clay particles mobilized less shear resistance and produced a greater compression.

Item Type: Journal Article Copyright of this article belongs to Clay Minerals Society. Division of Mechanical Sciences > Civil Engineering 26 Jun 2008 27 Aug 2008 13:31 http://eprints.iisc.ernet.in/id/eprint/14711