Interfacial characteristics and mechanical behavior of geopolymer stabilizers with clay mineral: A molecular dynamics study

There is a lack of research on the molecular interactions between clay minerals and geopolymers at the nanoscale, as well as the interfacial mechanism and mechanical behavior of geopolymers, as a highly promising sustainable soft soil reinforcement stabilizer (grouting reinforcement method). In this study, molecular dynamics simulations were used to reveal the interfacial characteristics and the molecular behavior of geopolymer stabilizers and clay minerals. Molecular models of two geopolymers (calcium aluminosilicate hydrate (C-A-S-H) and sodium aluminosilicate hydrate (N-A-S-H)) and two major minerals (montmorillonite and illite) in soft Hangzhou clays were developed. Then, the interfacial characteristics, interaction mechanisms and mechanical behaviors of different geopolymer/clay mineral interface systems were compared. It was found that montmorillonite and illite attract water molecules to aggregate on the mineral surfaces and promote the migration and diffusion of Ca2+ and Na+ at the interfaces. The interfacial interactions of the geopolymer/clay mineral system mainly consisted of electrostatic interactions. Stronger hydrogen bonding interactions occur at the interface of the geopolymer/clay mineral system. The metal cations and the geopolymer stabilizer between the clay mineral layers form a complex ion nest in concert with the aggregated water molecules to stabilize their interfacial interactions. In terms of the mechanical properties, the C-A-S-H stabilizer has a stronger interfacial shear strength. The shear strength of the illite system is stronger than that of the montmorillonite system, but montmorillonite can produce stronger interfacial bonding with the ground polymer stabilizer, and the curing effect is more obvious.