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

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.