Hydration of Cement

Hydration of cement begins when water is added to cement particles.

In the presence of water, the anhydrous cement compounds initially dissociate, releasing ions into the water that eventually form hydrates of silicates and aluminates in the solution and get precipitated, holding the cement grains in position.

Subsequent hydration takes place on the surface of the cement particles.

The hydration of silicates involves the reaction of tricalcium silicate and dicalcium silicate with water to form calcium silicate hydrate, the major product of hydration along with calcium hydroxide.

Although the hydration of C2S and C3S consume almost similar amounts of water, the hydration of C2S produces more C-S-H and less CH compared to C3S.

The hydration of aluminates initiates with the reaction of tricalcium aluminate with water in the presence of gypsum to form ettringite, which later transforms into calcium monosulfoaluminate hydrate.

In addition to this, the hydration of aluminates produces calcium aluminate hydrate and calcium aluminoferrite hydrate.

As long as the unreacted cement grains and free water in the mix come in contact, the hydration continues.