Geopolymerization in Fly Ash and Flotation Tailings: Thermodynamic Modeling

This study presents a thermodynamic modeling approach to the geopolymerization of fly ash (FA) and flotation tailings (FT), aiming to predict the physicochemical composition of the resulting geopolymers based on the input materials, alkali activators, and water. Simulations were performed using the GEM-Selektor software (Gibbs Energy Minimization) for four different FA-FT ratios (100%, 80%, 65%, and 50% FA). The model's predictions were validated against experimental data by comparing the geopolymerization products to structural and mechanical properties characterized via Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) and Unconfined Compressive Strength (UCS) measurements after 28 days of curing. The results demonstrated that increasing fly ash content led to greater formation of C-A-S-H phases. The model also underscored distinguishing between C-A-S-H and N-A-S-H proportions in evaluating material stability. Both experimental findings and literature emphasize maintaining optimal molar ratios of Ca/Si, Si/Al, and Na/Al to ensure geopolymer integrity. This model provides a valuable predictive tool for optimizing geopolymer formulations, reducing the need for extensive experimental trials.