Gel formation in concrete

C3S present in cement when reacts with H2O it forms C-S-H gel and CaOH2 (lime) with heat. This replaces the water and fills the voids in concrete. CaOH2 again reacts with SiO2 (silica) present in admix and again foms gel and fill the voids, hence this reaction continues inside concrete for years and increase its strength.

C3S produces 61% of gel and C2S produces 82% of gel. Hydration is a exothermic recation. C3S is  responsible for 7 days strength and C2S is responsible for 28 days strength.

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