Superplasticizers: How they Work and Why They Occasionally Don't

Abstract

This article discusses superplastcizers which are highly efficient dispersing admixtures when they are properly used. These compounds make it possible to increase concrete workability without addition of water; efficiently disperse cement particles so that concretes can be made using less water than needed for full hydration of cement particles; produce hydrated cement paste stable and dense enough to bond strongly to aggregates and reinforcing steel; and increase concrete density so that it can be stronger than many rocks. This article describes the nature of superplasticizers (characterization, specification, standards); how they work (deflocculation, etc.); efficiency; dosage; and potential problems (rheology, segration, overretardation, air-entraining admixture compatibility, etc.); and blended superplasticizers.