State and Location of Water Adsorbed on Clay Minerals: Consequences of the Hydration and Swelling-Shrinkage Phenomena

Abstract

Abstract--The application of the Frenkel-Halsey-Hiil (FHH) formalism to the water desorption isotherms obtained for the whole range of the activity of water with the pressure membrane device (0.98 < aw < 1) and with the desiccator (0 < aw < 0.98) gives information concerning the nature and the relative importance of the 2 mechanisms involved in the dehydration-hydration processes: adsorption and capillary condensation. The state and location of water are described in each domain. An equation that gives the thickness t of the film of water adsorbed on the walls of pores versus the activity of water is developed. This t-curve is used to get, from the desorption isotherm, the pore size distribution curve of the studied hydrated materials. Then concepts of surface and fabric of clay pastes are discussed as a function of hydration and a mechanism is proposed to explain swelling and shrinkage of finely divided materials. Three kinds of surfaces, related to the aggregate fabric, are defined as a function of their capacity to adsorb water. Each kind of surface is determined by a specific technique: the total surface area (St) by ethylene glycol adsorption, the external surface area of particles (S~) by nitrogen adsorption and the external surface area of aggregates (Se) by hydraulic conductivity measurements. As a consequence it is only with completely dispersed clays that swelling is a function of St. With unwell-dispersed clays, water adsorption, which induces swelling, successively occurs on St, S s and Se surfaces.

Experimental study and isotherm models of water vapor adsorption in shale rocks

“…In general, the FHH plot allows us to analyze and determine the states and location of water adsorbed in shale rocks verses relative humidity, which is very common in soil science (Prost et al, 1998). The FHH curves can be obtained by plotting log(water content (mg/g)) as a function of log(log(1/RH)), as shown in Fig.…”

“…Water will be adsorbed on the hydrophilic sites of shale. With relative humidity increasing, the multilayer adsorption in the domain 2 will occur on free surfaces, which are the walls of shale pores or surfaces that allow to expand freely (Ho, 2004;Prost et al, 1998). The domain 3 is observed for the higher RH and corresponds to capillary condensation.…”

Hydraulic Conductivity of Nonprehydrated Geosynthetic Clay Liners Permeated with Inorganic Solutions and Waste Leachates

“…There are two types in the interlayer expansion of montmorillonite; the osmotic swelling and the hydration swelling (van Olphen, 1977;McBride, 1994;Prost et al, 1998). The osmotic swelling occurs when the exchange sites in the interlayer contain monovalent cations (Norrish and Quirk, 1954;Posner and Quirk, 1964;Low, 1987;Chang et al, 1995;Karaborni et al, 1996).…”

Efeito da calagem na relação entre solo e água

“…O caráter hidrófilo-hidrófobo do solo pode variar em função da eletroquímica do solo (Prost et al, 1998;Chenu et al, 2001;Pernes-Debuyser & Tessier, 2004). É notório que superfícies sólidas têm afinidades diferenciadas pelas moléculas de água, sendo estimadas pelo ângulo de contato formado entre o menisco da gota de água sobre a superfície (Jouanny et al, 1992).…”