Q: I am using a superplasticizer in my concrete. I have heard that since this is a water-reducer, the need for curing water is reduced. Is this correct?
A: This is a perfectly logical, but incorrect conclusion. Superplasticizers (aka high-range water reducers), along with their cousins the normal- and midrange water reducers, have the ability to reduce the amount of water needed to achieve the desired level of workability. None of these products reduces the amount of water required to hydrate the cement. In fact, superplasticizers are so powerful that the resulting water content required for workability often is less than the amount of water that would sustain maximum hydration of the cement. This is usually the case with high-strength/high-durability mixtures with low water-to-cementitious materials ratios. Another way to look at it: Mixtures with low initial water contents can tolerate very little loss of water due to evaporation. For these types of mixtures, a thorough wet cure is even more important.
— Kenneth C. Hover, Ph.D., P.E., is a structural/materials engineer and professor of structural engineering at Cornell University, Ithaca, N.Y., and a popular speaker at Hanley Wood's World of Concrete.