As a natural product, bentonite is increasingly used in geotechnical engineering and environmental geotechnics due to its inertness and its characteristic properties. It is used in trench excavating, tunnel construction, grouting of cracks in bedrock soils, sealing of landfills, remediation of contaminated soils, etc. The outstanding and important properties of this material for the profession are undrained shear strength, viscosity, swelling potential, thixotropy, ability to bind certain pollutants and water permeability. The first three are discussed in more detail in this thesis, where we were interested in how selected properties of bentonite change when exposed to different saline or acidic (low pH) environments. The changes in properties due to different saline or acidic pore solutions were determined on two types of bentonite from the same manufacturer - calcium and sodium. Their behaviour was verified by laboratory tests to determine the liquid limit, undrained shear strength, rheological properties and swelling. The results were presented in tables or graphs then analysed and compared with each other. We critically commented on the influence of the specimen’s preparation and test procedures then assessed the usefulness of the tests for planning the targeted use of bentonites.
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