Dastgir:

C2S being hudrophilic, should have liberated any form of SO3 in water and may have modified setting behaviour of cement . But in case of pet coke use, no such modification is observed in cement setting behaviour.

Hello Gulam,

SO3 which gets incorporated into belite in high SO3 clinker, has the following effects;-

1. It stabilises the belite structure and prevents the uptake of CaO thus retarding the conversion of belite into alite.
2. It also retards the early hydration of belite.

This last point means that the SO3 which is is present in solid solution with belite is released too late in the hydration process to have much effect on set control.

It is the rapidly-soluble alkali sulphates and calcium langbeinite, K2Ca2(SO4)3, which  strongly influence set control in cements made with high SO3 clinker.

Regards,

Ted.