Fig. 2.11. Dependency of water density on adsorbed water content (after Lu and Lukos, 2004)

The density of water understood to be increasing with the decrease in gravimentric water content as shown in Fig. 2.11. The effect of surface characteristics of clays become more and more important for montmorillonitic clays. Such clays exhibit strong short-range interactive forces due to the presence of high specific surface area (~ 800 m² /g) and high surface charge density. It was observed that the density of pore water in sodium montmorillonite increases from 1.0 g/cm³ at full saturation (free water) to ~1.27 g/cm³ at residual condition (highly adsorbed state).