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Title: Alteration of Superplasticizers Molecular Composition during Adsorption on Cement Hydrates

Author(s): Anatoly I. Vovk

Publication: Symposium Paper

Volume: 329


Appears on pages(s): 175-184

Keywords: high-performance liquid chromatography; mechanism of superplasticizers; molecular mass distribution; preferential adsorption; unusual PNS fraction

DOI: 10.14359/51711213

Date: 9/26/2018

The mechanism of superplasticizers (SP) action implies their obligatory adsorption on the products of binder hydration; the magnitude and kinetics of adsorption determine the efficiency of initial plastification and of the effect retention. It is generally recognized that high-molecular components of SP adsorbed more than low-molecular analogs. However, this conclusion is based on comparison of adsorption levels for individual fraction of different molecular mass while SP comprise set fractions of different molecular mass and their adsorption occurs simultaneously as a competitive process. Polymethylene naphthalene sulfonates (PNS) are the very thoroughly studied class of superplasticizers (SP) and they are considered as suitable model to study sulfonate-type SP mechanism with Portland cement hydrates. Using High Performance Liquid Chromatography this paper examines for the first time effect of molecular mass on adsorption kinetic under competition and reveals some trends. The results obtained were compared with adsorption data by UV-spectroscopy. An applicability of identified trends for PCE was considered.