The Molecular Parameters and the Effect of Comb-Type Superplasticizers on Self-Compacting Concrete: A Comparison of Comb-Type Superplasticizer Adsorption onto a Basic Calcium Carbonate

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Title: The Molecular Parameters and the Effect of Comb-Type Superplasticizers on Self-Compacting Concrete: A Comparison of Comb-Type Superplasticizer Adsorption onto a Basic Calcium Carbonate

Author(s): C. Comparet, A. Nonat, S. Pourchet, M. Mosquet, and P. Maitrasse

Publication: Special Publication

Volume: 217

Issue:

Appears on pages(s): 195-210

Keywords: adsorption; alkali sulphate; calcium carbonate; polymer; superplasticizer

Date: 9/1/2003

Abstract:
Several superplasticizers were synthesised by an esterification reaction using commercial polymethacrylic acid and polyethylene oxide chains to produce comb-type polymers. These superplasticizers, with same main chain length, but different ester ratios were evaluated in self-compacting concrete (SCC) using cement with a high C3A and soluble alkali content. There is a strong relationship between the initial efficiency (flow value) and the carboxylic ester ratio of the polymeric material. In order to further understand this relationship, preliminary adsorption isotherms using a basic calcium carbonate suspension medium in the presence of these polymers, with and without an addition of sodium sulphate were investigated. The results show clearly that the level of adsorption in a basic calcium carbonate suspension medium decreases when the concentration of sodium sulphate increases, and strongly decreases when the comb-type polymers ester ratio increases. The results tend to show an effect of ionic strength and not an effect of ions influence.