ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 66, (4) 527 - 539 (2022)

Čeplak Barbara 1, Šter Katarina 2, Mrak Maruša 2, Škrlep Luka 2, Vrabec Mirijam 3, Dolenec Sabina 2
1 Geological Survey of Slovenia, Dimičeva ulica 14, 1000 Ljubljana, Slovenia
2 Slovenian National Building and Civil Engineering Institute, Dimičeva ulica 12, 1000 Ljubljana, Slovenia
3 University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Geology Aškerčeva 12, 1000 Ljubljana, Slovenia

Keywords: Belite-sulfoaluminate clinker, Clinker microstructure, Alkalis, Reactivity

This paper presents a study on the influence of different amounts of alkalis (K₂O and Na₂O) on clinker phase formation, microstructure, phase composition and reactivity of belite-sulfoaluminate cement clinker. Using X-ray powder diffraction and scanning electron microscopy with energy dispersive spectrometry, it was found that the amount of C₂S and C₄AF increases with the incorporation of alkalis, while the amount of C₄A₃Ś and CŚ decreases. In addition to the major phases, the samples with alkalis also consist of minor phases such as C₃A (tricalcium aluminate), KŚ (arcanite), and KC₂Ś₃ (Ca-langbeinite). The major ions in the major phases were substituted by alkali cations and some other ions (Ca2+, Al3+, Fe3+, S2-, S6+, Si4+). The alkalis also affect the microstructure of the clinker, e.g., the shape of the grains. Consequently, isothermal calorimetry was used to detect differences in hydration kinetics. The clinker with 2 wt. % K₂O content was the most reactive, while the sample with 0.5 wt. % Na content was the least reactive. The latter was primarily influenced by the content of the main and minor phases of the clinker.

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doi: 10.13168/cs.2022.0049
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