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The following steps demonstrate the chemical reactions, which occur during the forming process of Portland cement clinker. The presence of oxidizing conditions, during the clinker forming reaction, is critical to the production of Portland cement.

1. Decarbonation of Calcium Carbonate(Calcination)

CaCO3 ---->CaO + CO2 @1650 F

(Highly Endothermic)

2. Rapid neutralization of free lime (exothermic)

3CaO + Al2O3 ---->C3A

Melt (>2250 F)

2CaO + Fe2O3 ---->C2F

2CaO + SiO2 ---->C2S (Belite)

3. Formation of alite (slow reaction)

CaO + C2S ---->C3S (Alite)

(>2200 F)