Selecting the Optimum HRWR for SCC

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Title: Selecting the Optimum HRWR for SCC

Author(s): I. Schober and U. Mader

Publication: Special Publication

Volume: 235

Issue:

Appears on pages(s): 283-290

Keywords: adsorption; polycarboxylate; self-compacting concrete; superplasticizer

Date: 3/22/2006

Abstract:
Polycarboxylate type Superplasticizers have become the most widely used in SCC since they show outstanding performance regarding water reduction and flow retention. In some cases, depending on polymer structure and binder used, incompatibility problems like rapid slump loss may be observed. In order to overcome such problems, the mode of action of different polycarboxylates was studied by measuring the adsorption of the polymer on cement, the flow in cement paste, the flow and strength development in mortar as well as in standard concrete and self compacting concrete. The structure of the polycarboxylate (molecular weight, length of side chains, grafting degree) strongly influences its adsorption on cement and thus the performance as Superplasticizer. The increase of flow of the cement paste and polymer adsorption follows a quasi linear relationship. However the polycarboxylate with the highest adsorption is not necessarily the best performing in SCC applications. The outstanding performance of polycarboxylates in SCC and the importance of using a knowledge based approach for reaching the optimal properties of this materials is demonstrated in case studies.