Strength characteristics and carbonation depth evolution of modified magnesium slag based solid waste storage backfill materials

CO2 storage is one of the effective ways to achieve China's 30·60 dual carbon goal. The study of the interaction between CO2 and storage backfill material lays a foundation for the long-term stability and gas tightness of CO2 storage. Based on the modified magnesium slag-based solid waste backfill material constructed by the storage, in order to explore the strength characteristics and carbonation depth evolution of the CO2 storage backfill material, the interaction between CO2 and the storage backfill material was analyzed from the perspectives of uniaxial compressive strength, carbonation depth test, pore structure distribution, microstructure and phase composition. The results show that carbonation can significantly improve the compressive strength of the storage backfill material, and the carbonation depth increases with the increase of carbonation time, and increases slowly after complete carbonation. The later the initial carbonation age, the faster the growth rate of compressive strength and carbonation depth, and the greater the growth rate. After high concentration CO2 curing, the diffusion rate and carbonation degree of the storage backfill material gradually decreased from the outside to the inside, and the calcium carbonate content also gradually decreased. The carbonation can significantly reduce the porosity of the sample, gradually transform from large pores to small pores, and the pore size distribution and pore structure are significantly improved. Therefore, the later the initial carbonation age is, the more beneficial the carbonation effect is for the long-term stability and air tightness development of the backfill material of the CO2 storage, which provides important theoretical guidance for the construction and storage method of the CO2 storage.