Dynamic microstructure evolution of charged kaolinites with counterions during hydration—A large-scale molecular dynamics study

Abstract

As porous materials, clayey soils are very prone to lose strength under wetting, which may trigger catastrophic engineering accidents or natural disasters. However, the underlying triggering mechanism of pore water fluids at microscale remains unknown due to limited experimental techniques. In the present work, the dynamic hydration process of charged kaolinites with counterions has been fully explored by applying large-scale full-atomistic molecular dynamics. Topology study showed that the dry kaolinites hydrated immediately when exposed to water. Under the control of the ionic hydration effect, the ionic bridging effect, the water bridging effect and the surface adsorption effect, the adsorption behavior of interparticle water molecules experienced instantaneous adsorption, rapid adsorption and expulsion to reach dynamic equilibrium. The interparticle pore water pressure underwent rapid growth, slow growth and exponential growth along with the adsorption of water molecules. After fully hydration, the net distance between two kaolinite particles decreased by 1/5–2/5 with two or three layers of water molecules occupying the interparticle space. The reported results enhanced the comprehension of the dynamic microstructure evolution of kaolinite clay during hydration, which could further sketch interesting scientific avenues for future researches.