Geopolymerization in Fly Ash and Flotation Tailings: Thermodynamic Modeling

Authors

  • Marija Štulović Innovation Center, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia
  • Dragana Radovanović Innovation Center, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia
  • Nataša Gajić Institute for Technology of Nuclear and Other Mineral Raw Materials, Boulevard Franše d’Eperea 86, 11000 Belgrade, Serbia
  • Nela Vujović Institute for Technology of Nuclear and Other Mineral Raw Materials, Bulevar Franš ’d’Eperea 86, 11000 Belgrade, Serbia
  • Jovana Djokić Innovative Centre, Faculty of Chemistry, University of Belgrade, Studentski Trg 12-16, 11000 Belgrade, Serbia
  • Željko Kamberović University of Belgrade, Faculty of Technology and Metallurgy, Belgrade, Serbia
  • Sanja Jevtić University of Belgrade, Faculty of Technology and Metallurgy, Belgrade, Serbia

Abstract

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.

Keywords:

Geopolymer, Fly ash, Flotation tailings, Geopolymerization products, GEM-Selektor
Supporting Agencies
This work was supported by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Contract No. 451-03-136/2025-03/200287).

References

Abaka-Wood, G. B., J. Addai-Mensah, and W. Skinner. "The Concentration of Rare Earth Elements from Coal Fly Ash." Journal of the Southern African Institute of Mining and Metallurgy 122, no. 1 (2022): 7–15. https://doi.org/10.17159/2411-9717/1654/2022.

Capasso, I., B. Liguori, C. Ferone, D. Caputo, and R. Cioffi. "Strategies for the Valorization of Soil Waste by Geopolymer Production: An Overview." Journal of Cleaner Production 288 (2021): 125646. https://doi.org/10.1016/j.jclepro.2020.125646.

Gomez-Zamorano, L., M. Balonis, B. Erdemli, N. Neithalath, and G. Sant. "C-(N)-S-H and N-A-S-H Gels: Compositions and Solubility Data at 25°C and 50°C." Journal of the American Ceramic Society 100, no. 6 (2017): 2700–2711. https://doi.org/10.1111/jace.14715.

Kulik, D. A., T. Wagner, S. V. Dmytrieva, G. Kosakowski, F. F. Hingerl, K. V. Chudnenko, and U. R. Berner. "GEM-Selektor Geochemical Modeling Package: Revised Algorithm and GEMS3K Numerical Kernel for Coupled Simulation Codes." Computational Geosciences 17, no. 1 (2013): 1–24. https://doi.org/10.1007/s10596-012-9310-6.

Lazorenko, G., A. Kasprzhitskii, F. Shaikh, R. S. Krishna, and J. Mishra. "Utilization Potential of Mine Tailings in Geopolymers: Physicochemical and Environmental Aspects." Process Safety and Environmental Protection 147 (2021): 559–577. https://doi.org/10.1016/j.psep.2020.12.028.

Lèbre, É., G. D. Corder, and A. Golev. "Sustainable Practices in the Management of Mining Waste: A Focus on the Mineral Resource." Minerals Engineering 107 (2017): 34–42. https://doi.org/10.1016/j.mineng.2016.12.004.

Lothenbach, B., D. A. Kulik, T. Matschei, M. Balonis, L. Baquerizo, B. Dilnesa, G. D. Miron, and R. J. Myers. "Cemdata18: A Chemical Thermodynamic Database for Hydrated Portland Cements and Alkali-Activated Materials." Cement and Concrete Research 115 (2019): 472–506. https://doi.org/10.1016/j.cemconres.2018.04.018.

Lothenbach, B., E. Bernard, and U. Mader. "Zeolite Formation in the Presence of Cement Hydrates and Albite." Physics and Chemistry of the Earth, Parts A/B/C 99 (2017): 77–94. https://doi.org/10.1016/j.pce.2017.02.006.

Luhar, Ismail, and Salmabanu Luhar. "A Comprehensive Review on Fly Ash-Based Geopolymer." Journal of Composites Science 6, no. 8 (2022): 219. https://doi.org/10.3390/jcs6080219.

Ma, B., and B. Lothenbach. "Synthesis, Characterization, and Thermodynamic Study of Selected Na-Based Zeolites." Cement and Concrete Research 135 (2020): 106111. https://doi.org/10.1016/j.cemconres.2020.106111.

Ma, B., and B. Lothenbach. "Thermodynamic Study of Cement/Rock Interactions Using Experimentally Generated Solubility Data of Zeolites." Cement and Concrete Research 135 (2020): 106149. https://doi.org/10.1016/j.cemconres.2020.106149.

Myers, R. J., S. A. Bernal, and J. L. Provis. "A Thermodynamic Model for C-(N-)A-S-H Gel: CNASH_ss. Derivation and Validation." Cement and Concrete Research 66 (2014): 27–47. https://doi.org/10.1016/j.cemconres.2014.07.005.

Park, S., S. Park, S. Park, and S. Pyo. "Thermodynamic Modeling and Mechanical Properties of Hybrid Alkaline Cement Composites." Construction and Building Materials 322 (2022): 126381. https://doi.org/10.1016/j.conbuildmat.2022.126381.

Štulović, M., D. Radovanović, J. Dikić, N. Gajić, J. Djokić, Ž. Kamberović, and S. Jevtić. "Utilization of Copper Flotation Tailings in Geopolymer Materials Based on Zeolite and Fly Ash." Materials 17, no. 24 (2024): 6115. https://doi.org/10.3390/ma17246115.

Tchadjie, L. N., and S. O. Ekolu. "Enhancing the Reactivity of Aluminosilicate Materials Toward Geopolymer Synthesis." Journal of Materials Science 53, no. 7 (2018): 4709–4733. https://doi.org/10.1007/s10853-017-1907-7.

Thoenen, T., W. Hummel, U. Berner, and E. Curti. PSI/Nagra Chemical Thermodynamic Database 12/07. Nagra Working Report NAB, 2014.

U.S. Environmental Protection Agency. Method 1311: Toxicity Characteristic Leaching Procedure, Part of Test Methods for Evaluating Solid Waste, Physical/Chemical Methods. Washington, DC, 1992.

Vujović, N., V. Alivojvodić, D. Radovanović, M. Štulović, M. Sokić, and F. Kokalj. "Towards Circularity in Serbian Mining: Unlocking the Potential of Flotation Tailings and Fly Ash." Minerals 15, no. 3 (2025): 254. https://doi.org/10.3390/min15030254.

Wagner, T., D. Kulik, F. Hingerl, and S. Dmytrieva. "GEM-Selektor Geochemical Modeling Package: TSolMod Library and Data Interface for Multicomponent Phase Models." The Canadian Mineralogist 50, no. 5 (2012): 1173–1195. https://doi.org/10.3749/canmin.50.5.1173.

Wang, C., D. Harbottle, Q. Liu, and Z. Xu. "Current State of Fine Mineral Tailings Treatment: A Critical Review on Theory and Practice." Minerals Engineering 58 (2014): 113–131. https://doi.org/10.1016/j.mineng.2014.01.018.

Wang, S., B. Liu, Q. Zhang, Q. Wen, X. Lu, K. Xiao, C. Ekberg, and S. Zhang. "Application of Geopolymers for Treatment of Industrial Solid Waste Containing Heavy Metals: State-of-the-Art Review." Journal of Cleaner Production 390 (2023): 136053. https://doi.org/10.1016/j.jclepro.2023.136053.

Xu, H., and J. S. van Deventer. "The Geopolymerisation of Alumino-Silicate Minerals." International Journal of Mineral Processing 59, no. 3 (2000): 247–266. https://doi.org/10.1016/S0301-7516(99)00074-5.

Xiaolong, Z., Z. Shiyu, L. Hui, and Z. Yingliang. "Disposal of Mine Tailings via Geopolymerization." Journal of Cleaner Production 284 (2021): 124756. https://doi.org/10.1016/j.jclepro.2020.124756.

Published

31-03-2025

Issue

Section

Sustainable Industrial Waste Processing