Self-healing of hardened cement paste affected by additional Ca²⁺ and CO₃^2- ions with temperature control

A self-healing phenomenon, in which the cracks become partially refilled as a result of rehydration of cement particles and deposition of CaCO₃, has been observed in narrow cracks under a constant supply of moisture. Also, according to previous studies, the self-healing performance can be maximized by changing the temperature and pH to control the crystal form of CaCO₃. In this study, attention was paid to the crystal form of CaCO₃ generated in the self-healing process of a cement-based composite material and, in order to generate denser crystal of CaCO₃, the change in the crystal form of CaCO₃ generated in the hardened cement paste by changing the temperature condition was observed and analyzed. Also, to increase generation of CaCO₃ which is a self-healing precipitate, nano-sized ultrafine CO3^2- bubbles using CO₂ gas were used along with effective supply of Ca²⁺ through adjustment of aqueous solution. As a result, the possibility for effective generation and control of denser vaterite together with calcite was confirmed by adjusting the temperature to about 40°C under the condition of pH 12.