Diluting concrete with water to make it workable

[Rob Tucker]

What comes out of the truck is what is ordered. The concrete can be wet (high slump) or dry (low slump). The desired workability and work time is a matter of the mix design (test strength) including the wetness (slump).

Vibrators are needed depending on the use. Vibrators minimize or eliminate voids. The potential for voids increases with the dryness of the mix (low slump). Vibrators do not add test strength per se.

Haaheo okole puka is very correct on keeping the concrete surfaces wet during it's cure.