Study on the Carbon Dioxide Sequestration Properties of High-Magnesium Nickel Slag-Based Cementitious Backfill Materials

High-magnesium nickel slag (HMNS) is a type of metallurgical waste that has the potential for cementitious activity, and its high content of olivine minerals also makes it a potential for CO2 sequestration. We prepared HMNS-based cementitious backfill materials (HMNS-CBMs) using mechanical activation and chemical activation methods. Furthermore, we explored the sequestration efficiency of CO2 under accelerated carbonation conditions. The hydration products and carbonation products of the test blocks were analyzed by using a thermogravimetric-differential scanning calorimeter and X-ray diffraction. Additionally, the microstructure of the materials was analyzed by using mercury intrusion porosimetry and backscattered electron microscopy. Results showed that under carbonation conditions at 80 degrees C for 72 h, the HMNS-CBM had a CO2 adsorption content (CAC) of 6.62 wt.% after a 28-day water curing period. Moreover, under the same curing conditions, the compressive strength of HMNS-CBM treated with citric acid activation reached 49.35 MPa, which was the highest among all the studied samples. The addition of citric acid facilitated CO2 adsorption during the early water curing period and enhanced the development of compressive strength during the later water curing period.