A simplified view on chemical effects perturbing the action of superplasticizers

Understanding and quantifying effects of superplasticizers in concrete is a complex task. Even for nonreactive systems, such as ceramic suspensions, the stabilizing effects of dispersants are a subject of ongoing research. In cementitious systems, hydration reactions can perturb the behavior of suspensions. In this article, we propose three categories to describe the interactions and state of the superplasticizers with the cement suspensions. The first pail would be consumed by intercalation, coprecipitation or micellization, i.e., by the formation of an organo-mineral phase (OMP). A second part of the polymer could be adsorbed onto the surface of particles and help disperse cement agglomerates. The third part consists of the excess superplasticizer neither consumed nor adsorbed and which remains dissolved in the aqueous phase. Thus, at equal dosage, a cement with a larger degree of consumption (Part 1) could have a lower surface coverage and consequently poorer workability (for cements otherwise equal: specific surface, composition, etc.), unless an excess of superplasticizer is added to ensure saturation. Differentiating consumption from adsorption is essential for correct interpretation of experimental data, a fact that is not yet appreciated often enough and to which this paper attempts to draw larger attention. (C) 2001 Elsevier Science Ltd. All rights reserved.