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Title: Effect of the PCE Side Chain Length and Grafting Density on the Plastic Viscosity of Cement Paste

Author(s): David Nicia and Dirk Lowke

Publication: Symposium Paper

Volume: 354


Appears on pages(s): 25-34

Keywords: rheology of cement-based suspensions; plastic viscosity; polycarboxylate ether (PCE); PCE molecular structure; parallel-plate rheometry; PCE adsorption; cement paste; stickiness

DOI: 10.14359/51736059

Date: 7/1/2022

Molecular parameters of polycarboxylate polymers (PCEs) affect important rheological properties of cement-based suspensions such as viscosity. As the viscosity has a significant influence on the form filling ability and segregation resistance, understanding and predicting the effect of the side chain length and grafting density on viscosity is of considerable importance. To investigate the effect of tailored PCEs with systematically varying side chain length and grafting density on the plastic viscosity of cement paste, parallel-plate rheometry, TOC analysis, and spread flow measurements were performed. The results indicate that with decreasing side chain length as well as increasing grafting density, the plastic viscosity of cement paste with constant dynamic yield stress is reduced, with a dominating impact of the side chains. Furthermore, decreasing viscosity correlates with less non-adsorbed PCE. This finding could be related to the reduced viscosity of the interstitial aqueous phase, as less residual PCE and shorter side chains that protrude into the aqueous phase could reduce it. Hence, the macroscopic viscosity would decrease as well.