Influence of Salinity on the Consistency and Swelling Characteristics of Bentonite

Bentonite clay liners are used as a barrier material for water, chemicals and gas in civil
engineering structures such as engineered landfills and in structural water proofing. Bentonic clays
absorb water and expand greater than any other ordinary plastic clay. The expansiveness of the clay is
characterised by the absorbed cation in the clay and the geochemical environment. This paper
critically investigates factors that contribute to the swelling characteristics of bentonite clay and its
products. It takes particular view on different types of bentonite used in clay liners and their
interaction with saline ground water conditions. The swelling pressure of sodium bentonite in
deionised water is demonstrated to be very high. However when it is in a saline environment the
magnitude of swelling pressure can be less than halved. A parallel observation is noted under
conditions of free swell. These are explained as being a consequence of reduction in the double layer
thickness which is further reflected in the reduction of cationexchange
capacity when the bentonite is
in a saline environment. Variations in cation exchange capacity, consistency limit and free swell of
the bentonite products in different saline environment are observed and its significance discussed.

Citation:
Kreft, A. et al. (2009) ‘Influence of Salinity on the Consistency and Swelling Characteristics of Bentonite’ Proceedings of the AC&T, pp.102-111..