In this study, kaolinite, Ca-montmorillonite, and Na-montmorillonite were used as research objects to study the adsorption behavior of water molecules in clay minerals. The adsorption behavior of water molecules on the surface and interlayers of clay minerals was studied by density functional theory, XRD, Einstein viscosity theory, surface morphology, TG/DSC, and molecular dynamics. The experimental results show that under the same number of water molecules, the interlayer spacing of Na-montmorillonite increases slowly. After high-temperature dehydration, the interlayer spacing change of Na-montmorillonite is small. In the water-saturated state, the interlayer spacing of Na-montmorillonite is larger than that of Ca-montmorillonite. High-temperature removal of interlayer water has a small effect on the interlayer spacing of kaolinite. The thickness of the surface hydration film and the degree of hydration of Ca-montmorillonite are greater than those of Na-montmorillonite. The thickness of the surface hydration film of kaolinite (00-1) is greater than that of kaolinite (001), and the thickness of the surface hydration film and the degree of hydration of kaolinite are less than those of montmorillonite. The higher water absorption rate of Na-montmorillonite interlayers is the main reason for its higher water content than Ca-montmorillonite.
 

Montmorillonite,Kaolinite,Absorption expansion,Surface hydration