Mineralogical changes and geotechnical properties of an expansive soil interacted with caustic solution |
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Authors: | Puvvadi Venkata Sivapullaiah Gullapalli Sankara Mehter M Allam |
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Institution: | (1) Indian Institute of Science, Bangalore, India |
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Abstract: | The type and amount of clay mineral plays an important role in the behaviour of fine-grained soils. Clay minerals are the
primary source and moisture is often the external agent of swelling in soils. Also soils may exhibit increased/reduced swelling
due to interaction with chemicals. Alkalis used in industrial operations are one such example. Concentrations of alkali and
mineral type are the key factors in such interactions. The present paper reports the changes in the properties of an expansive
Black Cotton soil containing a mixed layer mineral, rectorite upon interaction with high concentration caustic solutions.
X-ray diffraction studies have shown that the rectorite present in the soil undergoes changes with increase in the concentration
of alkali. Saponite gets transformed to nantronite. Small amount of kaolinitic mineral present in the soil also reacts with
alkali producing some changes in its mineralogy. Many hydroxides are produced. Differential thermal analysis studies have
been supportive of these changes. Consequent of these changes, the soil-specific surface increases, changes its Atterberg
limits and free swell volume increases. The results have been supported by the characteristics and behaviour of samples contaminated
in the field with alkali from an alumina extraction plant. |
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