Every cubic yard or cubic meter of concrete, batched with ordinary portland cement, can readily benefit from the use of a conventional ASTM C494 certified water reducing admixture (WRA). The benefit can be realized in one of three basic ways relative to a reference mix without any admixture:
1. All the mixture proportions of the reference mix can be kept constant. Upon adding the water reducing admixture and increase in slump or workability can be realized. The amount of slump increase will be a function of the type (or chemistry) and dosage rate of the water reducing admixture.
2. With the addition of a WRA, the water content of the reference mix can be reduced (accompanied by an increase in fine and coarse aggregate). The resulting mixture will have increased strength and reduced permeability versus the reference mix.
3. Both the water and cement contents can be reduced proportionately, maintaining a constant w/c ratio. The resulting mixture will have approximately the same workability and strength at a lower production cost.
All these benefits are made possible by the action of water reducing chemicals on the inter-particle forces between hydrating cement grains. To learn more, an excellent course on chemical admixtures for concrete is available from Dr. Ara A. Jeknavorian.