Study on the Influence of CO<sub>2</sub>-absorbed CaCO<sub>3</sub> from Different Sources on the Strength of Blast Furnace Slag Cement Mortar

This study explores the relationship between the physical properties of CO2-absorbed CaCO3 and the strength of BFS cement mortar. Four CaCO3 powders with different specific surface areas and particle sizes were synthesized from industrial by-products. These CaCO3 powders were used to partially replace BFS cement in mortar. Compressive strength was evaluated, and pore structure was characterized using mercury intrusion porosimetry (MIP). Paste samples were further analyzed to determine hydration degree by thermogravimetric analysis (TG), while early hydration behavior was investigated through isothermal calorimetry and X-ray diffraction (XRD). Although the average particle size, particle size distribution, and specific surface area of CaCO3 from four different sources varied, the results suggest that CaCO3 with a higher specific surface area can promote the reactivity of BFS, refine the pore structure, and improve compressive strength, while coarser particles are conducive to the formation of carboaluminate, thus contributing to long-term strength improvement. These findings provide guidance for optimizing CaCO3 utilization in low-clinker cements and demonstrate the potential of synthetic CaCO3 derived from industrial waste to enable carbon-negative cementitious materials.