Study on physical properties of mortar for section restoration using calcium nitrite and CO₂ nano-bubble water

This study investigated the physical properties of section-restoration mortar with calcium nitrite (Ca(NO₂)₂) and carbon dioxide (CO₂) nanobubble mixing water to develop materials and methods for the repair and reinforcement of cracks in reinforced concrete (RC) structures. As the calcium nitrite content increased, the generation rate and generated amount of nitrite-based hydration products also increased, owing to the rapid reaction between NO₂^- ions in calcium nitrite and C₃A(Al₂O₃). Further, the reaction with C₃S and C₂S was accelerated, thereby increasing the generation rates of Ca(OH)₂ and C-S-H. The large amount of Ca²⁺ ions in these hydration products reacted with CO₃^2- ions in CO₂ nanobubble water, thereby increasing the generation of calcite-based CaCO₃ in the cement matrix. This appears to have affected strength development and durability improvement via the densification of the structure. These results suggest that the performance of polymer cement mortar for repairing concrete structures can be improved if calcium nitrite and CO₂ nanobubble water are properly combined and applied.