The influence of starting materials´ solubility on tobermorite structure formation under the hydrothermal conditions

Abstract

Overall, the tobermorite mineral crystallises under the hydrothermal conditions from the CaO-SiO2-H2O system. The system of calcium hydrosilicates species is extremely complex and many factors play an important role. The solubility of starting materials belongs to one of the most important factors. Dissolution rates of SiO2 source are significantly affected by their particle size distribution. Also the starting cation´s concentration in the aqueous solution affects the yield of the hydrothermal reaction. The main aim of this contribution is to study the influence of water-to-solid ratio on tobermorite crystallization. The effect of particle size of various sources of SiO2 was also studied. The cost effective Ca and Si sources was primarily favoured. The C/S ratio of the experiments was set to 0.83. All syntheses were performed at 180 °C in laboratory steel autoclaves. The prepared powdered samples were characterized in order to determine the phase composition by using of X-Ray diffractometry. The thermal behaviour of prepared samples was studied by TG-DTA analyser. Morphology and particle size of synthetized powdered products was studied by scanning electron microscopy.Overall, the tobermorite mineral crystallises under the hydrothermal conditions from the CaO-SiO2-H2O system. The system of calcium hydrosilicates species is extremely complex and many factors play an important role. The solubility of starting materials belongs to one of the most important factors. Dissolution rates of SiO2 source are significantly affected by their particle size distribution. Also the starting cation´s concentration in the aqueous solution affects the yield of the hydrothermal reaction. The main aim of this contribution is to study the influence of water-to-solid ratio on tobermorite crystallization. The effect of particle size of various sources of SiO2 was also studied. The cost effective Ca and Si sources was primarily favoured. The C/S ratio of the experiments was set to 0.83. All syntheses were performed at 180 °C in laboratory steel autoclaves. The prepared powdered samples were characterized in order to determine the phase composition by using of X-Ray diffractometry. The thermal behaviour of prepared samples was studied by TG-DTA analyser. Morphology and particle size of synthetized powdered products was studied by scanning electron microscopy.