CVG-2107 (Chapter 2) 15

CVG-2107 (Chapter 2) 15 - Let’s first define following...

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Prof. M. Fall - Uniersity of Ottawa Prof. M. Fall - Uniersity of Ottawa 15 Interaction water-clay mineral (swelling mechanisms) The exact mechanisms of water adsorption are complex, but include Water is strongly attracted to clay minerals and adsorbed by them. This is important, as the mechanical response of clay soils is greatly influenced by the degree of hydration of its clay particles. The exact mechanisms of water adsorption are complex, but include Hydrogen bonding between the surface oxygen anions of hydroxyl molecules and the dipolar water molecules. Hydration of exchangeable cations. Attraction by osmosis Interaction water-clay mineral (swelling meca.) Hydrogen bonding between the surface oxygen anions of hydroxyl molecules and the dipolar water molecules. Adsorbed layers 3 monolayers Kaolinite Oxygen Hydroxyl Clay Surfaces Free water Bulk water O OH H O H O H Interaction water-clay mineral (swelling meca.)
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Unformatted text preview: Let’s first define following terminology : Interlayer Interparticle Layer Particle Ion Hydration Interaction water-clay mineral (swelling meca.) The water molecules wedge into the interlayer after adding water Ion hydration Dry condition (Interlayer) Clay layers cation The cations are fully hydrated, which results in repulsive forces and expanding clay layers (hydration energy). Na + crystal radius: 0.095 nm radius of hydrated ion: 0.358 nm Interaction water-clay mineral (swelling meca.) Attraction by osmosis The concentration of cations is higher in the interlayers (A) compared with that in the solution (B) due to negatively charged surfaces. Because of this concentration difference, water molecules tend to diffuse toward the interlayer in an attempt to equalize concentration. From Oxtoby et al., 1994 A B Interaction water-clay mineral (swelling meca.)...
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