Carbonation of a Synthetic CAF Compound by CO₂ Absorption and Its Effect on Cement Matrix

In the field of construction materials, the development of fundamental technologies to reduce energy consumption and CO₂ emissions, such as manufacturing process improvement and the expanded use of alternative materials, is required. Technologies for effectively reducing energy consumption and improving CO₂ absorption and reduction that can meet domestic greenhouse gas reduction targets are also required. In this study, calcium-aluminate-ferrite (CAF), a ternary system of CaO·Al₂O₃·Fe₂O₃, was sintered at a low temperature (1100 °C) to examine the possibility of CO₂ adsorption, and excellent CO₂ absorption performance was confirmed, as the calcite content was found to be 11.01% after 3 h of the reaction between synthetic CAF (SCAF) and CO₂. In addition, the physical and carbonation characteristics were investigated with respect to the SCAF substitution rate for cement (10%, 30%, 50%, 70%, and 100%). It was found that SCAF 10% developed a compressive strength similar to that of ordinary Portland cement (OPC 100%), but the compressive strength tended to decrease as the SCAF substitution rate increased. An increase in the SCAF substitution rate led to the rapid penetration of CO₂, and carbonation was observed in all the specimens after 7 days. As carbonation time increased, the CO₂ diffusion coefficient tended to decrease. This is because the diffusion of CO₂ in the cement matrix follows the semi-infinite model of Fick's second law. SCAF can contribute to reduced energy consumption and CO₂ emissions because of the low-temperature sintering and can absorb and fix CO₂ when a certain amount is substituted.