Composition, hydration, setting and curing
Cements

Portland cement contains four main constituents:

• tricalcium silicate 3 CaO, SiO₂ (or, by abbreviation, C₃S);

• dicalcium silicate 2 CaO, SiO₂ (or C₂S) ;

• tricalcium aluminate 3 CaO, AI₂O₃ (or C₃A) ;

• tetracalcium-alumino-ferrite 4 CaO, AI₂O₃, Fe₂O₃ (or C₄AF).

By hydration, tricalcium silicate C₃S and bicalcium silicate C₂S give hydrated monocalcium silicate CSH, as well as hydrated free lime CH known as "portlandite", forming a microcrystalline gel at the origin of the so-called "setting" phenomenon...