Carbonation curing of modified magnesium-coal based solid waste backfill material for CO2 sequestration

CO2 sequestration is an effective method for dealing with the global climate crisis, and carbonation curing is considered an effective method of sequestering CO2 and improving the mechanical properties of cement-based materials (CBM). Regarding modified magnesium-coal based solid waste backfill material (MB), to explore its carbonation curing performance and CO2 sequestration capacity, its uniaxial compression strength (UCS), carbonation depth, microstructure, CO2 transport performance, CO2 uptake capacity, and carbonation efficiency are analyzed and characterized using UCS tests, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) analysis. The results show that the early UCS of the MB is significantly improved by carbonation curing. The UCS at 7 days is 10.91 times higher than that of the MB without carbonation curing, and the UCS increases as the concentration and modified magnesium slag-based cementitious material (MC) content increase. Carbonation curing makes the microstructure of the MB significantly denser and reduces the porosity, pore diameter, and permeability. The formation of carbonated products such as calcium carbonate and hydration products makes the microstructure more compact, which is the main reason for the rapid increase in the early UCS of the MB. The maximum CO2 uptake capacity of the MB through carbonation curing is 14.3%, and the carbonation efficiency is up to 92.2%. Therefore, carbonation curing of MB has broad application potential in improving the UCS and sequestering CO2.