The use of alkaline CO₂ solvent for the CO₂ curing of blast-furnace slag mortar

Moving toward carbon neutrality in the construction industry involves utilizing CO2 to produce construction materials. CO2 curing of cement-based materials induces carbonation at an early age, which enhances strength and performance. A new process for the CO2 curing is proposed using CO2-dissolved curing water, which needs no massive CO2-gas chamber encasing cement-based materials in mild pressure. Gaseous CO2 was dissolved in 1 M aqueous KOH solution beforehand, and mortar samples made with ground-granulated blast furnace slag were submerged and cured. The CO2-water curing for 3 days carbonated the samples, but was not beneficial for their 3-day strengths. Successive moist curing resulted in further hydration of the mortar with carbonate seeds. Finally, the samples' strengths at 28 days were enhanced, and their CO2 uptake was as much as the conventional CO2 curing provides.