Study on the mesoscopic mechanical properties of carbonated steel slag fine aggregate concrete based on CT scanning

To investigate the influence of carbonated steel slag fine aggregate on the compressive properties and mesoscopic failure mechanism of concrete, a combined approach integrating macroscopic experiments and mesoscopic numerical simulation was adopted. Carbonated steel slag fine aggregate was used to replace natural sand at equivalent volume ratios. The applicability of steel slag was first verified through volume stability tests. Steel slag concrete with replacement ratios ranging from 0% to 30% was prepared for macroscopic mechanical tests. Meanwhile, a mesoscopic numerical model was established based on CT scanning, Avizo, MATLAB, and Abaqus, and its reliability was validated to analyze the mesoscopic damage evolution behavior. The results indicated that an appropriate amount of steel slag can enhance the compressive strength of concrete. For the non-carbonated group, the compressive strength reached the maximum at a 20% replacement ratio, whereas the carbonated group consistently exhibited higher strength than the corresponding non-carbonated group, with an increase of approximately 3–8% at the same replacement ratio. The prediction error of the mesoscopic model was less than 3%. In addition, steel slag altered the damage evolution behavior and failure mode of concrete, while carbonation treatment improved crack propagation behavior. This study clarifies the mesoscopic mechanism by which carbonated steel slag affects the compressive properties of concrete, providing a scientific basis for the failure analysis and engineering application of steel slag concrete.