Laboratory analysis reveals contrasting effects of sodium and calcium on bentonite gel strength, indicating that cation valence and initial exchange status determine clay stability.
The effect of cations on the gel strength of a bentonite clay was studied by measuring the maximum yield value of clay salt mixtures. Cations which are in large concentration as exchanged ions on the clay act very differently upon the clay strength than do cations which are only in trace concentrations in the clay. For those cations which were originally in only trace concentrations, the ability to build up the gel strength is inversely proportional to their valence. Sodium and calcium ions reacted completely differently. The clay was tolerant to a large sodium concentration but lost gel strength with the addition of only a small amount of calcium. This result is explained in the light of previously reported ion exchange properties of clay.
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Hu et al. (1974) studied this question.
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