Résumé
Geopolymers are a type of alkali aluminosilicate polymer that are synthesized from a liquid precursor. Over the past several years, we have been conducting a joint theoretical and experimental investigation into the formation of geopolymers at various length and timescales. This work presents significant challenges due to the complex nature of geopolymer formation.Our first objective was to separate the high-pH effect, caused by the alkali-based solutions used to dissolve the metakaolin, from the aluminum effect. We found that these two effects counteract each other. Through simulations of aluminosilicate formation at high pH, using parallel tempering molecular dynamics, we observed the formation of grains with a size of approximately 1 nm, which is consistent with values measured using small-angle X-ray scattering (SAXS).In addition, we have been examining the interaction between two aluminosilicate grains in solution from a fully atomistic perspective using metadynamics. This has allowed us to reconstruct a potential of mean force for the interaction between two grains at the scale ofa few nanometers. For example, we have observed that the size and aggregation of grains is controlled by pH in a consistent manner with respect to the experiments and simulations at the molecular level.Our multi-scale simulation approach provides new insights into the mechanisms governing the formation and properties of geopolymers. This understanding can guide the design and optimization of new geopolymer materials and processes.