Pre-carbonation of calcium carbide slag for the preparation of eco-friendly mortars

• Published in: Construction & building materials 2023-10, Vol.399, p.132541, Article 132541
• Main Authors: Chen, Peiyuan, Wang, Chunjie, Wang, Yonghui, Xie, Jiankai, Shen, Xin, Wang, Cheng, Wang, Jialai
• Format: Article
• Language: English
• Subjects: CaCO3; Calcium carbide slag; CO2 uptake; Pre-carbonation; Seeding effect
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.132541

•Pre-carbonation can be a solution to the incompatibility of calcium carbide slag with cement.•The generation of CaCO3 through the carbonation of calcium carbide slag refined the pore structure of mortars.•The carbonation process of calcium carbide slag was characterized.•Calcium carbide slag can be a good CO2 absorbent. To promote the utilization of high-calcium and high-alkali calcium carbide slag (CCS) in the construction industry, a pre-carbonation method has been employed to convert Ca(OH)2 in CCS to CaCO3 to improve the compatibility of CCS with cement. The study investigated the effects of different carbonation durations (10 min, 20 min, and 30 min) on the performance of CCS mortars. Results showed that 30 min carbonation duration for CCS achieved a 24.83% CO2 uptake and converted 92.2% of Ca(OH)2 to CaCO3, thereby reducing the pH of the CCS suspension from 12.5 to 11.4. Moreover, the carbonation process generated CaCO3, which acted as seed and filling effects, accelerating, and promoting the hydration of the mortar. This led to an optimized pore distribution and a denser microstructure at 28d. The mortar with carbonated CCS for 20 min demonstrated the highest compressive strength, exhibiting an enhancement of 0.8% to 41.4% at 3d, 7d, and 28d compared to un-carbonated CCS mortar. These experimental findings provide a sustainable and efficient solution for the consumption of CCS in the construction industry.