Contrasting Influence of Caustic Alkali on the Behavior of Two Swelling Soils


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by P. V. Sivapullaiah, Associate Professor; Department of Civil Engineering, Indian Institute of Science, Bangalore-560 012, India, siva@civil.iisc.ernet.in,
G. Sankara, Research Student; Department of Civil Engineering, Indian Institute of Science, Bangalore-560 012, India,
M. M. Allam, Professor; Department of Civil Engineering, Indian Institute of Science, Bangalore-560 012, India,



Document Type: Proceeding Paper

Part of: Advances in Unsaturated Soil, Seepage, and Environmental Geotechnics:

Abstract: Investigations were carried out to bring out the effect of varying concentration of caustic alkali, NaOH, solutions on the volume change behaviour of two swelling soils containing different types of clay minerals. The effect of contamination is studied not only during contamination but also on already contaminated samples. Bentonite and natural Indian black cotton soil containing interstratified illite-smectite mineral were contaminated with caustic soda solutions of 1 N and 4 N concentration. The oedometer tests revealed abnormal volume change behaviour in Black cotton soil during unloading. This has been attributed, to mineralogical alterations as suggested by XRD and DTA studies. Dissolution of interlayer potassium from interstratified illite-smectite due to interaction with alkali solution has led to the separation of unit layers of the interstratified mineral causing swelling. In bentonite characteristic swelling is restricted and compressibility has decreased due to changes in the thickness of diffuse double layer rather than mineralogical changes.

Subject Headings: Soil properties | Alkalinity | Expansive soils | Minerals | Pollution | Soil classification | Volume change | Bentonite | Crops |

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