The water cement ratio has a direct relation with the strength of concrete.water cement ratio law states that the strength of concrete is only dependent upon w/c ratio provided the mix is workable.
When the w/c ratio increases beyond the practical limit the concrete exibits a tendency for separation of constituent particles ( Segregation ) and some of the water also comes out of concrete(Bleeding) being of the lowest specific gravity among all the ingredients of concrete.
With increase in water cement ratio, the amount of water in concrete increases, which affects sample in following ways.
Strength:- The strength decreases with increase in water cement ratio.
Workability:- The Workability increases with increase in water cement ratio, but higher water cement ratio can lead to bleeding and segregation of concrete mixture.
Compaction:- For proper compaction, less compactive efforts are required for higher water cement ratio.
Void ratio:- For higher water cement ratio the no. of voids in concrete sample will be high after curing period, which inturn will affect the strength.