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A Contractor's Guide to Superplasticizers

Using high-range water reducers, also known as superplasticizers, to increase slump may be necessary for difficult wall placements. Conditions like narrow forms, heavy reinforcement, and sections with many blockouts, penetrations, or embedded items require the use of high-slump concrete. Superplasticized concrete also works well for pumping operations. The fluid concrete consistency reduces pump pressures and eliminates the need for altering mix designs for pumping great heights. It can also eliminate the need to use staging pumps. But what types of superplasticizers are there, and how do you choose the best type for the job? When should you add superplasticizers to the mix? How will a change of brands affect set time and slump loss? High-range water reducers are classified by ASTM C 494, "Standard Specifications for Chemical Admixtures for Concrete", as Types F and G. Type F is a water-reducing, high-range admixture, and Type G is a water-reducing, high-range, retarding admixture. Within the different ASTM types, manufacturers offer many different brands. Different brands may produce different results.