Formulas for C3S and C2S calculation

For C3S calculation we have to mines free lime from total CaO and its Clare. What about C2S, do we have to mines free lime from total CaO, and if yes, why? Thank you in advance BR

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re Formulas for C3S and C2S calculation

Hello GLT,

No it is not necessary to compensate for free lime in the Bogue equation for C2S.
This is because C2S forms first in the kiln by the reaction of silica caontaining minerals and lime i.e.;

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

Only after this reaction has occured can C3S then form by the reaction of C2S with more CaO i.e;

2CaO.SiO2 + CaO ---> 3CaO.SiO2 (C3S)

Any CaO left over in the clinker after this last equation has reached equilibrium is called free lime.

Therefore since the free lime did not react with C2S to form C3S, it only needs to be subtracted from the total CaO in the C3S calculation.

Hope this helps...

Regards,Ted.

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