Microfabric characteristics of kaolinite flocculates and aggregates — Insights from large-scale molecular dynamics simulations

Abstract

Clay particles are usually associated in flocculates or aggregates with different microfabric manners, which will govern the macroscale mechanical behaviors of clayey soils. In this study, the characteristics of different microfabric manners of defect-free kaolinite were explored applying large-scale full-atomistic molecular dynamics simulations. Due to the special crystal structure, kaolinite particles were more likely to flocculate in Edge-to-Face (EF) and Edge-to-Edge (EE) manners than aggregate in Face-to-Face (FF) manner when analyzed from the system energy point of view. For EF and EE manners, the 1st layer of adsorbed water of every single kaolinite particle was complete while the 2nd and the 3rd layers of adsorbed water arranged in T-, L-/inverted L- or cross-shape according to the wettability performance of surrounding kaolinite particles' surfaces. A series of new schematic diagrams of different microfabric manners with adsorbed water structures were developed according to the corresponding equilibrium topologies and physicochemical characteristics. The conceptual hypothesis of the kaolinite sedimentary process was verified and improved based on the simulation results analysis. The research results enhanced the comprehension of microfabric characteristics of clay colloids. The simulation method applied in this work would foster future investigations into clay colloids in various physicochemical environments.