Concrete mix designs
Water is the life blood of concrete. Without it, hydration and strength gain would not continuously occur. Concrete is one of those rare things that get stronger with age. Providing it stays moist throughout its life.
In order to make concrete, a very specific amount of sand and aggregate is combined with cement. The cement is hydrated with water to make glue.
If only the amount of water needed to hydrate cement were put into the mix, the slump would be virtually zero and the mix would be difficult to move.
In order to facilitate a workable mix, water in addition to that which is needed for hydration is added for convenience” (WoC) needed to make concrete workable is subject to the conditions and specification of the slab. Very few slab-on-grade specifications cite the ratio of water and compressive strength.
The WoC however, occupies physical space in the slab. When evacuated over a long period of time, the result is a degree of porosity that is determined by how much WoC was in the mix design.
In fast-track construction, WoC which has not evacuated sufficiently can lead to problems with floor installation. In older slabs, increased porosity that resulted from a high WoC can allow environment moisture to be drawn through the slab to the surface where it can lead to problems with the floor.