Other effects of cooling rate

C3S is sufficiently intimately mixed with either C2S or CaO. Some substituent ions affect the rate Al has little effect, Fe markedly accelerates, Na slightly retards, and Mg markedly retards decomposition. Where both and Fe are present, the accelerating effect of the Fe is dominant. The decomposition is also accelerated by water vapour and, very strongly, by contact with sulphate melts with a CaS04-Na2S04 melt, decomposition was complete in 2 h at 1025 C. 

All the effects described above indicate that rapid cooling is desirable the aluminate phase reacts more slowly with water when finely grained and intimately mixed with ferrite, making it easier to control the setting rate (S24), decrease in alite content either from reactions involving the interstitial material or from decomposition is avoided, a higher MgO content can be tolerated, and the clinker is easier to grind. 

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