• Korean Chemical Engineering Research
• /
• v.57 no.5
• /
• pp.666-671
• /
• 2019

Calcium carbonate involves three phases such as calcite, vaterite, and aragonite. Calcite and aragonite were more thermodynamically stable than vaterite. The synthesis of aragonite crystals by the reaction with sodium carbonate and calcium chloride solutions was investigated focusing on the effect of temperature and rpm in continuous crystallizer. In the batch crystallization test, calcite was synthesized by a relatively low temperature (under $40^{\circ}C$), but aragonite was formed at high temperature. In the continuous process with 100 rpm, no aragonite was found regardless of reaction temperature. But as increasing the stirring rate to 300 rpm and 500 rpm, the ratio of aragonite to calcite increased as increasing the temperature.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.151-152
• /
• 2023

This study investigates the effect of nano-silica and nano-calcite on the hydration properties and mechanical performance of limestone calcined clay cement (LC³) paste. The pastes were synthesized by replacing limestone with nano-silica and nano-calcite in order to enhance the mechanical properties in both early and late stages of hydration. The nano-calcite enhanced the strength of LC³ pastes at 1 day of hydration, however, the strength decreased compared to the ordinary LC³ pastes afterwards due to excessive amount of carboaluminate produced in the pastes. On the other hand, nano-silica improved the mechanical properties of LC³ pastes at all ages of hydration. This is mainly due to the nucleation effect and pozzolanic reaction of nano-silica, affecting the early age and late ages of hydration, respectively. The nucleation effect of both nanomaterials were confirmed by the analysis of hydration heat, supporting the enhanced early age strength of nanomaterial incorporated LC³ pastes. Furthermore, the dense matrix was shown in the pore size distribution, and the increased C-S-H due to the pozzolanic reaction evidence the improved compressive and splitting tensile strength of nano-silica incorporated LC³ pastes.