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

Ceramics-Silikáty 64, (3) 239 - 248 (2020)

Smalakys G., Siauciunas R.
Department of Silicate Technology, Kaunas University of Technology, Radvilenu pl. 19, LT- 50299 Kaunas, Lithuania

Keywords: Hydrothermal synthesis, 1.13 nm tobermorite, X-ray diffraction analysis, Simultaneous thermal analysis

This study presents the peculiarities that occur during the hydrothermal synthesis of 1.13 nm tobermorite from granite sawing powder waste and CaO. The molar ratios of the primary mixtures were CaO/SiO₂ = 0.83 and 1.0; a hydrothermal curing temperature of - 180 and 200 °C; a duration of - 4, 8, 12, 24, 72 h. The instrumental analyses (XRD, STA, SEM, TMA) data showed that this industrial by-product is a suitable material to synthesise of 1.13 nm tobermorite. Traces of the aforementioned mineral together with semi-amorphous C-S-H(I) were detected after 4 h at 180 °C. The crystallinity of the target mineral in the products grows steadily throughout the entire duration of the synthesis (up to 72 h at 180 °C). By increasing the temperature of the hydrothermal curing to 200 °C, the highest crystallinity of the 1.13 nm tobermorite was identified after 8 h of isothermal curing. Due to the chemical composition of the granite sawing powder waste, the 1.13 nm tobermorite remains stable and does not recrystallise into xonotlite even after 72 h at 200 °C in mixtures with CaO/SiO₂ = 1.0.

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doi: 10.13168/cs.2020.0013
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