Carbonation curing of cement-based materials by using potassium glycine solution: Uniformly CO₂ sequestration and secondary strengthening

In this research, an internal carbonation curing method was proposed to achieve inside-outside synergistic carbon capture and performance improvement of cement-based materials. Potassium glycine (KG) solution with various concentrations was used as the CO₂ carrier. The results indicate that the addition of CO₂-rich KG solution increases 7-d and 28-d compressive strength by 29.8% and 16.2%, as well as achieving an overall CO₂ uptake of 4∼11% in cement paste. However, at higher KG concentrations, the rapidly generated amorphous calcium carbonate covers the surface of cement particles, which shortens the setting time and inhibits early-age hydration. The presence of carbamate in CO₂-rich KG solution improves the stability of metastable CaCO₃ polymorphs and prolongs the period of dissolution-recrystallization. Calcite generated by the slowed recrystallization within 14 days having a filling and binding ability in the cement matrix, significantly reducing porosity and providing a secondary strengthening effect.