Effects of solutes on clay–water interactions: Some comments

Schmitz [Schmitz, R.M., 2006. Can the diffuse double layer theory describe changes in the hydraulic conductivity of compacted clays? Geotechnical and Geological Engineering, 24, 1835–1844.] suggests that ‘unique interpretations and predictions of changes in hydraulic conductivity in clays’ follow appropriate interpretation of changes in double layer thickness. Existing data, however, suggest that reality is more complicated and that both the water content-water potential and hydraulic conductivity functions of clay–water systems must continue to be regarded as macroscopically measurable material properties and that double layer considerations provide only qualitative indications of general behaviour. At the same time, the composition of the equilibrium solution remains a necessary characteristic of the hydrostatic and dynamic properties of clay–water systems. Some experiments that might help our understanding of the hydrostatics and hydrodynamics of these systems are suggested.