2025 Volume 32 Issue Supplement Pages S99-S105
In this study, the formation of amorphous calcium carbonate (ACC) from calcium oxide and quicklime by a dry process was investigated. ACC was formed in the process of air slaking and carbonation of CaO. As CaO sources, calcium oxide and quicklime produced by heating precipitated calcium carbonate and limestone were used. The effects of relative humidity (RH) levels of 50% and 65% were also examined. ACC was already formed when each CaO was converted to calcium hydroxide. When calcium oxide was used, the maximum amount of ACC was formed at －24 h at 50% RH. By contrast, the amount of ACC produced with quicklime reached a maximum at －50 h. In this case, the maximum amount of ACC produced was －5% higher for calcium oxide. The time to produce ACC was 1.3 to 2.4 times longer with quicklime than with calcium oxide. Higher humidity resulted in faster hydration and carbonation and a shorter ACC production time, but no change was observed in the maximum amount of ACC produced.
