The water–cement ratio is the ratio of the weight of water to the weight of cement used in a concrete mix.
For easy placement of concrete it is a general practice to mix more water, which can badly affect the quality as well as strength of the concrete. Too much water will result in segregation of the sand and aggregate (stone chips) from the cement paste. Also concrete will experience more shrinkage as the excess water leaves, resulting in internal cracks and visible fractures (particularly around inside corners) which again will reduce the final strength.
However, a lower water-cement ratio leads to higher strength and durability, but may make the mix more difficult to place.
Therefore it always advised to stick to the correct water cement ratio so as to get a workable concrete mix for easy placement and proper compaction without compromising the strength of the concrete.
As per general practice for 1:1½:3 concrete mix 25-30 liters water should be added per 50 kg of cement (one bag) depending upon the temperature, humidity and water associated with sand and aggregate (if any).