| Abstract | The early-age impacts of CO₂ activation (using a dose of 0.3% CO₂ by weight of cement) on two binder systems (tricalcium silicate and cement) were studied, principally across the first 3 h of hydration. The investigation included calorimetry, ICP-OES, TGA, and SEM. The in-situ mineralization of CO₂ accelerated the hydration of both the systems, with the effect being more pronounced in cement. During the first 30 min of hydration, the CO₂ addition impacted the solution phase pH and certain elemental concentrations (Ca, Mg, S). At later times of observation, the values were comparable to the level of the reference sample. Thermodynamic modeling revealed that the presence of CO₂ resulted in stronger undersaturation with respect to the binder phases, which implies a strong driving force for their dissolution. The carbonates were observed in SEM micrographs as a multitude of rhombohedral-shaped calcite crystals while TGA confirmed an increased quantity of carbonates in both binder systems. |
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