Study on damage energy evolution and characteristics of concrete subjected to supercritical CO ₂ based on acoustic emission technique

Constructing CO2 reservoirs in abandoned mine goafs supports China’s “dual carbon” goals. To clarify damage evolution in concrete linings under supercritical CO2 (SC-CO2), this study conducted SC-CO2 immersion tests, uniaxial compression tests, acoustic emission (AE) monitoring, and SEM analyses on concrete specimens, and subsequently developed a quantitative damage constitutive model based on cumulative AE ringing counts.Results indicate: (1) Compared to natural conditions, SC-CO2 exposure significantly improves the peak strength and elastic modulus of concrete, with maximum enhancements of 14.81% and 61.65% observed at 65°C for 3 days. (2) At 35–65°C, increased temperature and duration reduce dissipated energy at compaction points and raise elastic energy at peak points, resulting in minimal initial damage and the strongest damage resistance at 65°C for 3 days; conversely, 80°C increases dissipated energy, decreases elastic energy, and intensifies damage. (3) AE cumulative counts decrease at medium-low temperatures but recover at 80°C, reflecting that high temperatures exacerbate damage. (4) 35–65°C promotes calcium carbonate formation, filling pores; 80°C converts it to leachable calcium bicarbonate, causing mechanical degradation. These findings support safety evaluations for deep goaf CO2 storage.