Liquid limit of mixtures of smectite, kaolinite and quartz powder with water and NaCl solution

Abstract

Clay mineralogy plays an important role in determining the mechanical properties of clayey materials. Several liquid limit and water uptake tests were performed on kaolinite-smectite mixtures for different quartz powder content and water and / or NaCl content as pore fluids. To interpret the results, the diffuse double layer theory is used. The experimental results show the effect of quartz powder in reducing the liquid limit of smectite with water and 1 M NaCl as fluid. A linear relationship is obtained from the tests. The quartz powder acts only to dilute the liquid limit values. To better understand the behavior of the clays regarding the liquid limit, predicted values for the liquid limit of all the mixtures with water and NaCl as pore fluid have been developed assuming the linear law to be valid. The prediction is very good for water, but it becomes less good with lower liquid limit values/higher quartz contents. The correlation with NaCl as fluid is not that good when the quartz content is high. A correlation of water uptake and liquid limit is also presented. The data fit is good. The overall results confirm that the effect of the pore fluid type is significant when the smectite content in the mixture is high.