Study on the Influence of CO₂-absorbed CaCO₃ from Different Sources on the Strength of Blast Furnace Slag Cement Mortar

Abstract

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.