Effect of salt of various concentrations on liquid limit, and hydraulic conductivity of different soil-bentonite mixtures

Mishra, A.K.; Ohtsubo, M.; Li, L.Y.; Higashi, T.; Park, J.

Environmental Geology (Berlin) 57.5

2009


DOI: 10.1007/s00254-008-1411-0
Accession: 037040819

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Abstract
Effect of the various concentrations of Na Cl and Ca Cl2 on the four different soil-bentonite mixtures has been evaluated. The results show that the liquid limit of the mixtures decreases with an increase in the salt concentration. Liquid limit decreased significantly with an increase in Ca Cl2 concentration from 0 to 0.1 N. However, a further increase in the concentration did not produce any significant decrease in liquid limit. A quite opposite trend was observed for the Na Cl solution. An increase in Na Cl concentration from 0 to 0.1 N did not produce any major decrease in the liquid limit, but a further increase in concentration from 0.1 to 1 N decreased the liquid limit significantly. Consolidation tests were carried out on the mixtures to evaluate the effect of mineralogical composition of the bentonite on the hydraulic conductivity (k) of the mixture in the presence of various salts concentrations. The k for any mixtures was found to be decreasing with decrease in the salt concentration. At relatively low concentration, Ca2+ had more effect on the k in comparison to the same concentration of Na+. However, at 1 N of Na Cl and Ca Cl2 almost an equal value of k was observed. A comparison of the performance of four bentonites showed that the mixture with bentonite having highest exchangeable sodium percentage (ESP) exhibited the lowest k when permeated with de-ionized (DI) water, however, k increased with an increase in the salt concentration. Similarly, mixture with a bentonite of lower Esp exhibited a higher k with Di water but with the increase in the salt concentration alteration in the k, compared to all other mixtures, was relatively less.

Effect of salt of various concentrations on liquid limit, and hydraulic conductivity of different soil-bentonite mixtures