Impact of pre-carbonation duration on carbonation-induced physicochemical changes in OPC

Carbonation curing of cement composites enhances mechanical properties while enabling permanent CO₂ sequestration. This study examines the influence of pre-carbonation duration and carbonation regimes on OPC paste, optimizing CO₂ uptake and physicochemical performance. Carbonation was initiated after 0, 3, 7, or 24 h of hydration for 3-hours at either 15 or 60 psi. Two post-carbonation curing methods were assessed: moist curing for 28 days or extended carbonation (48 h) followed by moist curing. Compressive strength, Thermogravimetric-Analysis (TGA), X-Ray-Diffraction (XRD), Fourier-Transform Infrared-Spectroscopy (FT-IR), Scanning-Electron-Microscopy (SEM), pH, and drying shrinkage analyses evaluated phase composition, microstructure, and mechanical performance. Results indicate that shorter pre-carbonation durations (0–3 h) enhanced CO₂ uptake and strength via calcium carbonate formation, whereas extended pre-carbonation reduced efficiency. Higher carbonation pressure (60 psi) had minimal impact. Increased carbonation elevated drying shrinkage, but subsequent hydration maintained it within acceptable limits (<500µm). These findings optimize early carbonation strategies for improved OPC paste performance.