Structural properties and mechanical responses of geopolymer pore models under chloride exposure: Molecular dynamics simulation

Geopolymers are aluminosilicate materials and are an environmentally friendly alternative to Portland cement. However, the presence of nanoscale gel pores in geopolymers can affect their structural properties. At the molecular level, the main component of the geopolymer is sodium aluminosilicate hydrate (NASH). Therefore, this study uses molecular dynamics simulations to investigate the impact of various NaCl concentrations on NASH pore structures, revealing significant ion interaction mechanisms. The results showed that as the NaCl concentration increased, the adsorption rate of Na+ ions on the NASH surface increased and Cl− ions diffused together with the Na+ ions. Besides, the presence of NaCl had little effect on the elastic modulus and ultimate strength of NASH, but the ability of the model to resist deformation varied with different degrees of hydroxylation in the model. This article offers a nanoscopic explanation of geopolymer performance in a chloride environment, facilitating enhancements in the optimal design of materials. [Display omitted] •The presence of NaCl made the NASH pore model anisotropic.•NaCl had little effect on the elastic modulus and ultimate strength of the model.•Hydroxylation enabled the model to resist deformation.•High NaCl concentration resulted in a high adsorption rate of Na + on the NASH surface.•High NaCl concentration caused a small difference between the MSD of Cl− and Na+.