Molecular dynamics simulation of the initial stage induction of alkali-activated aluminosilicate minerals

Abstract

With the increasing global concern over carbon emissions, geopolymers have garnered significant attention due to their energy-saving, waste utilization, and eco-friendly advantages. Metakaolin and slag, as aluminum-containing mineral materials in geopolymer production, have been widely studied and applied. Previous research has mainly focused on performance design and theoretical development, while the underlying mechanisms at the microscopic level remain unclear. In this study, we employed molecular dynamics simulations to investigate the microscale reaction behavior of geopolymers, exploring the induction process and structural evolution during the initial stages, and revealing the similarities and differences under alkali activation for different materials. Our findings indicate that the alkali activation process can be divided into two stages: mineral crystal deconstruction and oligomer polymerization. The role of NaOH differs between low-calcium and high-calcium systems, where in the low-calcium system, Na⁺ substitutes Ca²⁺ due to Ca²⁺ deficiency, participating in the formation of the network framework. Moreover, the high-calcium system exhibits a faster formation of the gel phase during alkali activation compared to the low-calcium system. This study provides valuable insights into the research and application of geopolymers.