*Proceeding Paper* **Geopolymers Based on Fly Ash from the Bełchatów Power Plant †**

**Agnieszka B ˛ak \* , Patrycja Bazan , Kinga Pławecka and Michał Łach**

Faculty of Material Engineering and Physics, Cracow University of Technology, Jana Pawła II 37, 31-864 Cracow, Poland

**\*** Correspondence: agnieszka.bak@pk.edu.pl

† Presented at the 10th MATBUD'2023 Scientific-Technical Conference "Building Materials Engineering and Innovative Sustainable Materials", Cracow, Poland, 19–21 April 2023.

**Abstract:** Geopolymer materials are attracting increasing interest from scientists due to their specific properties and the possibility of using waste materials from the power industry for their production. The most common raw material for their production is fly ash from the combustion of hard coal in pulverized coal boilers, but it is also possible to use ash from the combustion of lignite for this purpose. This article presents the results of a study of geopolymers produced with the use of ashes from lignite combustion at the Bełchatów Power Plant. It includes characterization of the ashes (laser particle size analysis, SEM/EDS morphology, XRD phase composition) and the strength properties of geopolymers made from these ashes and activated with 10 M and 14 M aqueous sodium hydroxide solution with water glass. As a result of this study, it was found that it is possible to obtain geopolymers characterized by flexural strength of almost 3 MPa and compressive strength of 30 MPa. A comparison of activators with concentrations of 10 M and 14 M made it possible to conclude that, due to the lack of significant differences in the properties of the obtained geopolymers, from an economic point of view, it is more advantageous in this case to use activators with a lower concentration.

**Keywords:** geopolymers; fly ash; fly ash from lignite; Belchatów; alkaline activation; flexural strength; compressive strength
