Forced Internal Carbonation and Curing in Lc3 Blends Made With Different Cement Types

The construction industry significantly contributes to global carbon emissions, underscoring the need for sustainable strategies to mitigate its environmental impact. This study examines the two-fold effect of carbonic acid mixing and curing on four cement paste mixes: ordinary Portland cement (OPC), sulfate-resisting cement (SRC), limestone calcined clay cement (LC3) with OPC, and LC3 with SRC. Isothermal calorimetry showed no significant changes in hydration kinetics. Early compressive strength testing revealed comparable results when either carbonic acid mixing or curing was applied individually, with LC3 mixes exhibiting slightly higher later-age strengths than plain cement mixes in non-carbonated conditions. However, the two-fold approach, i.e., simultaneous mixing and curing with carbonic acid, led to a 12.9% to 30.6% reduction in the 28-day compressive strength compared to the mixes without carbonation. Contrary to expectations, X-ray diffraction (XRD) detected no significant CaCO₃ formation, suggesting inconclusive carbonation effects. Despite some strength reduction with carbonic acid treatment, LC3 mixes demonstrated a denser microstructural matrix than plain cement mixes. Scanning electron microscopy (SEM) images further confirmed this density, indicating that LC3 w/ SRC mixes consistently maintained relative compressive strengths in cases of partial carbonation.