Exploring the Strength Formation Mechanism of Coal Gangue and Ground Granulated Blast Furnace Slag‐Based Geopolymer Using Molecular Dynamics

The research into the molecular dynamics (MD) behaviour of coal gangue (CG)–ground granulated blast furnace slag (GGBFS) geopolymers contributes to uncovering the strength formation mechanism of geopolymer. Geopolymers were prepared by using CG and GGBFS, and Na 2 SiO 3 as alkali activator. This study systematically investigated the unconfined compressive strength (UCS) and microstructure of geopolymers via a synergistic approach combining experimental testing and MD simulation. A validated C(N)–A–S–H molecular model was established, and the polymerisation characteristics were revealed through microstructural and kinetic analyses.The results indicate that the UCS of alkali‐activated CG‐ground‐granulated blast furnace slag geopolymer increases with curing age. Furthermore, the design of appropriate mix proportions can result in geopolymers with high UCS. Prepared with a GGBFS content of 40%, an alkali activator content of 25%–26% and an alkali activator modulus of 0.8–1.0, achieved a UCS of 34.1 MPa at 28 days of curing. MD simulations were performed to obtain three kinetic parameters, including the radial distribution function (RDF) analysis, the mean square displacement (MSD) analysis and the potential energy components (PEC). Analysis based on RDF indicates that systems with appropriate bond lengths and excellent coordination environments correspond to higher macroscopic mechanical properties, whereas excessively long bond lengths and distorted coordination structures lead to a reduction in macroscopic mechanical properties. The optimal formulation (40% GGBFS, 26% alkali activator, modulus 1.0) achieves 34.1 MPa at 28 days, attributed to ideal bond lengths and low degree of coordination distortion. The trends in the MSD and UCS are primarily influenced by the synergistic effects of the Si/Al and Ca/Si ratios.Furthermore, the system exhibits optimal UCS when the Ca/Si ratio exceeds 0.27, and the Si/Al ratio exceeds 2.0. A Pearson correlation analysis between PEC and UCS revealed a strong positive correlation between the two. This indicates a potential trend of association between micro‐energy and UCS. These findings provide valuable insights into the preparation mechanisms of geopolymers.