Impact of microstructure on the hydraulic conductivity of undisturbed and artificially prepared smectitic clay

The microstructure controls most physical properties of clays. This is obvious when comparing natural smectitic clay and clay prepared by drying, grinding and compression of air-dry powder. The hydraulic conductivity of the artificially prepared clay is higher than that of the undisturbed, natural clay. If the latter clay is percolated with distilled water and Ca-rich water, the difference in conductivity is obvious, while percolation of the natural clay with these solutions does not yield a very dramatic change. This is because the microstructure of the natural clay is very homogeneous, while the artificially prepared clay preserves the high density of the powder grains while the gels in the voids between the grains are soft.