The ratio of the volume of water to volume of cement used in a concrete mix is called water cement ratio.
By Water. Cement ratio Law
According to water cement ratio Law, "For any given condition of test, the strength of well compacted Concrete with good workability is dependent only on the water cement ratio."
The workability of Concrete is dependent to other factors like grading of Concrete, proportion of aggregates, proportion of cement, and the efficiency of mixture etc. Also depends upon the quantity of water used in the mixture.
According to Abram law the strength of mixture increases not merely by increasing the quantity of cement in the mix but it is an account it of reducing the water cement ratio the strength of concrete in accordance with the the law is given by modified formula.
P28= 984/4^x
Where P28 = Cylinder Crushing Strength of Concrete in Kg/cm^2
X= Water Cement ratio by volume
The observation results, it is observed that for a given proportion of ingredients in a design concrete mix, there is almost a certain around of water (optimum) which gives maximum strength.
A small changes in the quantity of water reason much higher variation in the strength of concrete.
In case the water used is less, the resultant concrete will be comparatively dry, difficult to place in position and may pose problems in compaction.
Moreover, with less water complete setting of cement cannot be ensured and hence the strength of concrete get reduced appreciably.
On the other hand, in case the water is more it would Tesult in formation cr excessive voids and honey-combing in the set concrete, thereby reducing its density, strength and durability.
so that, water cement ratio determine as a yard stick for achieving concrete of define strength.
The lower the water cement ratio, the larger is the strength of the Design mix of Concrete.
A rich mix of concrete gives higher strength than a lean mix, not because of more cenent but it is on account of the fact that concrete can be used with a lower water cement ratio.
