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Gypsum Effect on the Aggregate Size



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Gypsum Effect on the Aggregate Size and Geometry of Three Sodic Soils Under Reclamation I Lebron D L Suarez and T Yoshida ABSTRACT the soil particles and aggregates Dispersion or flocculation of clays occurs because of the repulsion of similar charged clay platelets and the ability of the soil solution to mitigate this repulsion Irreversible changes in soil structure may occur when clay particles become dislodged if for example the electrolyte level is decreased or the Na fraction increases There are several studies in which the decrease of Ksat has been related with increases in Na content McNeal and Coleman 1966 Frenkel et al 1978 Shainberg and Letey 1984 Suarez et al 1984 However there is no quantification to our knowledge of the repercussion that increases or decreases of Na have on the soil structure while water flow is occurring Flocculation slacking and aggregate stability studies show that increases in ESP cause dispersion and a decrease in aggregate stability and aggregate size but these tests are performed in fractions of the soil placed in sieves or test tubes Despite all the information collected in the laboratory there are some doubts about our capability to predict the extent of aggregation and dislodging in real soils Explanation for the clay behavior has been typically based in the Derjaguin Landau Verwey and Overbeek DLVO model this theory has been used successfully to explain a great number of laboratory experiments Unfortunately there is evidence that the electrical double layer interactions between charged particles in confined geometries are different than in isolated environments Larsen and Grier 1997 Grier 1998 Bowen and Sharif 1998 Sader and Chan 1999 Grier 1998 and Bowen and Sharif 1998 found that isolated pairs of like charged spheres behave as predicted by DLVO theory but spheres confined by a concentration of other spheres develop long range attractions inconsistent with DLVO Dilute systems may not properly represent the soil scenario as



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