Water-Strength Connection in Concrete

The ratio of water to cement in mixing concrete can controlled to ensure that the concrete reaches the specified strength. Adding more water when mixing concrete makes it easier to work with, but it creates two big problems: the concrete gets weaker (can't hold as much weight) and it shrinks more as it dries (causing cracks). On site, contractors should add the minimum amount of water needed to make the concrete workable. The sketch shows that adding just 2 gallons of water per cubic yard of concrete makes it 10% weaker and causes 20% more shrinkage. This is why properly mixed concrete is so important for things like driveways and house foundations.