THERMODYNAMIC SIMULATION OF FLY ASH AND FLOTATION TAILINGS GEOPOLYMERISATION PROCESS

Abstract

This work aims to develop a thermodynamic model for the geopolymerisation process of fly ash (FA) and flotation tailings (FT) with a prediction of the physicochemical composition of the geopolymers based on the initial materials (FT, FA), alkali reagents, and water. Modeling was carried out using the thermodynamic model (Gibbs Energy Minimization Software) GEM-Selektor. The simulation was done for the four compositions of geopolymer mixtures (100%, 80%, 65%, and 50% of FA). The validation of the thermodynamic simulation relies on experimental results. It involves comparing the geopolymerization products predicted by the model with those obtained through experimental quantification. This comparison focuses on the structural and mechanical properties of the geopolymers, specifically using techniques such as Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) and measuring the Unconfined Compressive Strength (UCS) of geopolymer materials for 28 days of curing. The simulation results from the model confirmed an increase in the quantity of C-A-S-H formed with the addition of FT. Additionally, the results indicated that distinguishing between the proportions of C-A-S-H and N-A-S-H is crucial for predicting material stability. According to both the experimental results and the literature, it is important not to exceed the optimal limits for the three parameters studied: Ca/Si, Si/Al, and Na/Al molar ratios. This model can be utilized to predict and enhance understanding of how various parameters affect the final composition of geopolymers. This approach will help minimize the number of trials needed to investigate these parameters and optimize them.