Assessing CO2 uptake of CO2-cured cement mortar through theoretical modeling and experimental validation

•A practical model framework is developed to assess the CO2 uptake of cement mortar.•High-concentration CO2 accelerates diffusion process and has little effects on carbonation process.•The CO2 uptake for different sizes of specimens tends to be the same after sufficient curing.•Achieving overall curing is an effective way to ensure high carbonation rate and CO2 uptake. CO2 curing of cement-based materials is considered a promising carbon–neutral technology for large-scale storage of CO2, and CO2 uptake is the key parameter for evaluating CO2 storage capacity. This study assessed the CO2 uptake of cement mortar subjected to flue gas curing through theoretical modeling and experimental validation. It is found that the CO2 uptake for the high-concentration group is higher at early stages but becomes the same after sufficient curing, asthe higher CO2 concentration accelerates the diffusion process but has little effect on the carbonation process. Meanwhile, although the initial CO2 uptake for the smaller specimens is larger, the difference gradually decreases with curing time after overall curing. Achieving overall curing is an effective way to ensure high carbonation rate and CO2 uptake. The CO2 uptake at overall curing increases with increasing specimen size or decreasing CO2 concentration. For fixed-depth CO2 curing, the CO2 uptake decreases significantly with increasing specimen size, while the curing time and carbonation degree change little. The findings of the present work will be beneficial to improve the CO2 storage capacity of cement-based materials and push forward the application of CO2 capture, utilization and storage (CCUS) technology in the construction industry.