Nature and Properties of Water in Montmorillonite‐Water Systems

Low, Philip F.

doi:10.2136/sssaj1979.03615995004300040005x

Cited by 154 publications

(99 citation statements)

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“…This leads to Equation (21) between the air pressure and the pedostructural macro and micro water contents at equilibrium W eq mi and W eq ma . This equation is similar to the empirical equation found by Low and Margheim (1979) between the applied pressure and the water content of the clay pastes in the membrane press apparatus and that Low (1979) expressed such as:…”

Section: Discussion Comparison With the Membrane Press Results Of Lowsupporting

confidence: 78%

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Soil water thermodynamic to unify water retention curve by pressure plates and tensiometer

et al. 2014

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The pressure plate method is a standard method for measuring the pF curves, also called soil water retention curves, in a large soil moisture range from saturation to a dry state corresponding to an applied pressure of near 1500 kPa. However, the pressure plate can only provide discrete water retention curves represented by a dozen measured points. In contrast, the measurement of the soil water retention curves by tensiometer is direct and continuous, but limited to the range of the tensiometer reading: from saturation to near 70-80 kPa. The two methods stem from two very different concepts of measurement and the compatibility of both methods has never been demonstrated. The recently established thermodynamic formulation of the pedostructure water retention curve, will allow the compatibility of the two curves to be studied, both theoretically and experimentally. This constitutes the object of the present article. We found that the pressure plate method provides accurate measurement points of the pedostructure water retention curve h(W ), conceptually the same as that accurately measured by the tensiometer. However, contrarily to what is usually thought, h is not equal to the applied air pressure on the sample, but rather, is proportional to its logarithm, in agreement with the thermodynamic theory developed in the article. The pF curve and soil water retention curve, as well as their methods of measurement are unified in a same physical theory. It is the theory of the soil medium organization (pedostructure) and its interaction with water. We show also how the hydrostructural parameters of the theoretical curve equation can be estimated from any measured curve, whatever the method of measurement. An application example using published pF curves is given.

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Section: Discussion Comparison With the Membrane Press Results Of Lowsupporting

confidence: 78%

“…where Low (1979) was thinking, namely that could be identified to the swelling pressure (−ρ w μ w ).…”

Section: Discussion Comparison With the Membrane Press Results Of Lowmentioning

confidence: 99%

Soil water thermodynamic to unify water retention curve by pressure plates and tensiometer

et al. 2014

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“…The firmly bound water molecules are thought to form the inner hydration sphere of the interlayer cations (water bound directly to cations), while the readily removable water consists of outer sphere water molecules H-bonded to each other in the interlayer region (Farmer and Russell 1971). The water molecules bound to the interlayer surfaces in montmorillonite have been predicted to have higher H-O-H stretching vibrations than bulk water (Low 1979(Low , 1981, but it is not uniformly accepted that these "surface" bonded water molecules have significantly different H-O-H stretching vibrations than other highly H-bonded interlayer water molecules (Sposito et al 1983).…”

Section: Water In Montmorilionitementioning

confidence: 99%

Infrared Spectroscopic Analyses on the Nature of Water in Montmorillonite

Bishop

Pieters

Edwards

1994

Clays and clay miner.

373

256

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Abstract--Interlayer cations and moisture content greatly influence the molecular vibrations of H20 in montmoriUonite as shown through reflectance spectroscopy in the infrared. The absorptions due to H~O have been studied in montmorillonites exchanged with H, Na, Ca, Mg and Fe 3+ interlayer cations under variable moisture environments. Band assignments have been made for absorptions in the 3 ~tm region due to structural OH vibrations, symmetric and asymmetric 1-120 stretching vibrations and the H20 bending overtone. Changes in the energies of the absorptions due to H20 stretching vibrations were observed as the samples were dehydrated by reducing the atmospheric pressure. Absorptions near 3620 cm -1 and 3550 cm -1 have been assigned to water bound directly to cations (inner sphere) and surfacebonded H20 and absorptions near 3450 cm -1 and 3350 cm ~ have been assigned to additional adsorbed water molecules. Band assignments have been made for combination bands in the near-infrared as well. Absorptions near 1.41 ~m and 1.91/zm are assigned to bound H20 combination bands, while the shoulders near 1.46 izm and 1.97 ~*m are assigned to combinations of additional H20 molecules adsorbed in the interlayer regions and along grain surfaces.

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“…This is known as osmotic swelling [15]. It occurs when diffuse clouds of positively charged ions overlapping the clay minerals cause the mineral structures to entirely delaminate and peptise to form a colloidal suspension [16]. Compaction of sodium bentonite will increase the overlap of diffuse clouds and the effect of osmotic swelling (Fig.…”

Section: Theory Of Waterproofing With Claymentioning

confidence: 99%

Clay barriers for protecting historic buildings from ground moisture intrusion

2017

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Background: Conservators and architects working with built heritage at risk from ground moisture intrusion face a difficult choice. Leaving the building unprotected can lead to moisture related deterioration; installing vertical and/ or horizontal barriers using standard materials requires chemical or mechanical intervention with the historic fabric. The use of compacted clay to form a barrier is commonplace in some areas of environmental engineering, and can be applied to built heritage conservation. Naturally occurring or slightly modified soils were traditionally used for protecting buildings in a number of vernacular techniques. Knowledge of what types of soils are suitable for use could provide certain regions with a low-cost, low-impact alternative for protecting historic buildings. Three commercially available products previously shown to have low hydraulic conductivity were analysed in order to identify waterproofing mechanisms; these included two specialised bentonite-sand mixtures and a Saxonian glacial till. Results:The till relies on a high proportion of densely agglomerated fine grains to achieve a low permeability when consolidated, possibly assisted by the presence of calcite. The specialised mixtures rely on an engineered grain size distribution, with practically no silt sized grains, and a fraction of sodium bentonites capable of forming colloidal suspension when compacted. All materials showed a low risk of shrinkage when compacted at optimum moisture content. Conclusion:Different mechanisms appear to account for the low hydraulic conductivities found in clay barrier material. The implication is that a range of soil material may be suitable for protecting built heritage from ground moisture intrusion and its associated decay mechanisms. The suitability of glacial till may present large areas of Northern Europe with locally available barrier material.

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Nature and Properties of Water in Montmorillonite‐Water Systems

Cited by 154 publications

References 0 publications

Soil water thermodynamic to unify water retention curve by pressure plates and tensiometer

Soil water thermodynamic to unify water retention curve by pressure plates and tensiometer

Infrared Spectroscopic Analyses on the Nature of Water in Montmorillonite

Clay barriers for protecting historic buildings from ground moisture intrusion

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