Clinkering process sulphates

The simultaneous presence of sulphate ions with alkalis somewhat decrease the process rate, but it is farther much higher than for CaO. Thus it can be assumed that in industrial clinkers the C2S dissolution rate is from three to five times higher than this of calcium oxide. 

The raw mix for clinker production should contain some excess of gypsum, because the vapour pressure of CaSO is higher than of C4A3S which decomposition is thus prevented. The presence of anhydrite in the clinker is not unfavorable, only lower amount of this compound must be added to the grinding process. Some amount of free CaO is beneficial too, as it was discussed earlier. The sulphate spurrite ( 28)208 phase is sometimes produced at low temperature and at about... 

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