Investigations for Chemical Parameters Effect on Swelling Characteristics of Expansive Soils

A comprehensive understanding of the chemical parameters effect can greatly aid in selecting the most compatible additive and stabilization technique to treat expansive clays. In the present study, influence of chemical parameters (total, leachable and exchangeable forms of sodium and calcium) on swelling (swelling potential, Sa, and swelling pressure, Sp) and consistency properties is quantified by relating them in the form of histograms. It is, in general, noticed that swelling property increases, reaches a peak, and thereafter, decreases with an increase in sodium (Na) and calcium (Ca) content. The value of Ca, Na, and Ca/Na ratio induced maximum swelling to soils are measured in the range of 3–7%, 0.5–0.8%, and 8–11.5 for total, 75–103 mg/kg, 108–164 mg/kg, and 0.7–1.12 for leachable, and 0.8–2.5 and 50–100 meq/100 g, 2–6 meq/100 g, and 0.2–0.5 for exchangeable forms. Three forms including, total, leachable, and exchangeable are found to have a distinct impact on swelling property. The results revealed that Ca/Na ratio, not the individual Ca or Na content, is the better parameter to estimate Sa and Sp of soils. Pertinent to exchangeable form, it is noticed that (a) the range within which Na has pronounced effect on Sa, the impact of Ca in the same range has obscured, (b) Ca/Na ratio, which varied over wider range from 2–120, could be a potential parameter for classifying expansive soils, and (c) exchangeable Ca has no bearing on Sp regardless of its intensity. From the results of the study, it is recommended for expansive clays to accord importance to chemical parameters of the above prescribed limits to design effective foundation systems, avoid swelling induced damage to superstructure, identify the most practicable additive, and select remedial technique to mitigate swelling.