Water Requirement for Hydration:

For building of concrete the water is majorly needed for the following purposes:

(a) For hydration of cement compounds.

(b) For giving proper lubrication between the concrete ingredients to make the concrete workable in plastic stage.

(c) After hardening of concrete, water is required for curing purpose. Requirement of water for workability and curing has been discussed, in detail, in separate units. The requirement of water for hydration is as below:

About 23 percent water through weight of cement is needed for the hydration of cement compounds and about 15 percent water is needed to fill the gel pores.

The gel pores are the pores of very small size and are part of hydrated cement gel. The water occupied within the gel pores is not available for further hydration. So, about 38 percent water by weight of cement is generally considered as sufficient to complete the hydration process along with occupying the space of gel pores. Any excess quantity of water than above will lead to form the capillary pores in the concrete mass and such water is free to evaporate leaving capillary pores behind, which reduces the strength of concrete. Therefore, it is quite necessary to monitor the quantity of water for preparation of concrete mix.