7. Cement evolution

The reactions that take place right from the start of the mixing process and continue over time are extremely complex.

Portland cement contains four main constituents:

• Tricalcium silicate 3 CaO, SiO2 or C3S for short;

• dicalcium silicate 2 CaO, SiO2 or, by abbreviation, C2S ;

• tricalcium aluminate 3 CaO, AI2 O3 or, by abbreviation, C3A ;

• tetracalcium alumino-ferrite 4 CaO, Al2 O3, Fe2 O3 or, for short, C4 AF.

In the presence of water, these anhydrous constituents give rise to silicates, hydrated calcium aluminates and hydrated lime known as "Portlandite", which form a microcrystalline gel and give rise to the phenomenon known as "setting".