“It is the ratio of water and the weight of the cement used in a concrete mix.”
It is denoted as
WC = Wt. of water/
Wt. of cement
It has an important influence on the quality of concrete produced. A lower WC ratio leads to higher strength and durability but may make the mixture more difficult to place; placement difficulties can be resolve by using plasticizer.
The WC ratio is independent of the total cement content or total water content of a concrete mix.
Often the w/c characterize as the water, cement + pozzolane ratio (wt of water/C+P)
(Pozzolane is material that can be used as binding material)
A pozzolane is typical a fly ash or blast Furness slag it includes a number of other material such as silica fume, rice hull ash or natural pozzolane. The addition of the pozzolane will influence the strength gain of the concrete. Concert hardens has a result of chemical reaction between water and cement known as hydration.
For every 4lb of cement 1 lb of water is needed to fully complete the reaction
Cement = 4 lbs
Water = 1 lbs
This results in a WC ratio of 25 % (¼×100 = 25%)
in reality a mix formed with 25% water is to dry and does not flow well enough to the place and same of the water is taken up by the sand and stone and is not available to participate in the hydration reaction so more water is used that is technically necessary to reach with the cement mostly a typically WC ratio of35% – 45% are used, to much water will result in settling and segregation of concrete component( more sand in the top layer because the stone will settled at the bottom) any water that is not consume by the hydration reaction will eventually leave the concrete as it hardens, resulting in microscopic porous or holes that will reduce the final strength of concrete and finally a mix with to much water will experience more shrinkage as the excess water leaves resulting in internal cracks and visible fractures, this can be reduced by keeping the water to an absolute value( suitable value)