The article presents the test results and the analysis of selected properties of bentonites used as isolation barriers of engineering structures, especially landfills. Three types of bentonites were used as a research material and for each of them the dispersivity and swelling ability were assessed. The dispersivity was determined by using the crumb test and the double hydrometer test. Swelling index was determined in the Holtz and Gibbs method and in the method presented in ASTM D 5890-95. The investigations of the influence of liquid pollution with various chlorides concentrations (1000, 2500, 5000 and 10,000 mg·dm^–3) on swelling ability of bentonite were included. The results obtained were compared with values required for typical bentonite materials used as isolation barriers of engineering structures.

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