*Proceeding Paper* **The Use of Calcined Diatomite as an Additive to Geopolymeric Materials †**

**Kinga Pławecka \* , Agnieszka B ˛ak , Maria Hebdowska-Krupa and Michał Łach**

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

**\*** Correspondence: kinga.plawecka@pk.edu.pl; Tel.: +48-576547854

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

**Abstract:** Diatomites are mineral resources formed from diatoms. They are widely used in sorption processes, medicine, cosmetology, and in protecting animals from parasites. Attempts are being made to incorporate them into concretes and construction binders to improve various performance properties. This paper presents the results of analyses (particle size analysis, XRD, and SEM) of a fine fraction of non-calcined and calcined diatomite as an additive to geopolymers made from fly ash from lignite combustion. The fly ash was also analyzed in the same way. Diatomite was introduced in its calcined and non-calcined form at 10%, 15%, and 30% by weight, replacing parts of the filler sand. The geopolymer mixtures were activated with 10 and 14 M aqueous sodium hydroxide solution with sodium water glass. As a result, it was found that it was possible to obtain geopolymers with diatomite additives with a compressive strength of about 34 MPa. In addition, after the strength tests, the microstructure of the obtained geopolymers was analyzed by scanning electron microscopy.

**Keywords:** diatomite; geopolymer materials; ash from lignite combustion
