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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Changes in Cement Paste and Mortar Fluidity after Mixing Induced by PCP: A Parametric Study
Author(s): L. Regnaud, A. Nonat, S. Pourchet, B. Pellerin, P. Maitrasse, J.P. Perez, and S. Georges
Publication: Special Publication
Appears on pages(s): 389-408
Keywords: adsorption; fluidity; over-fluidification; PCP; slump flow; sulfate
Abstract:The interaction mechanism between polycarboxylate-type superplasticizer (PCP) and cement hydration is not fully understood and incompatibilities between concrete and additive are sometimes observed. In some cases, the fluidity tends to increase ("over-fluidification") few minutes after mixing. This is a problem because the over-fluidification leds to bleeding of the concrete which could be critical on job site. Our study consisted first in highlighting the phenomenon of "over-fluidification" by slump flow tests on mortar. Next, the time evolution of the rheological behaviour of cement pastes in the presence of PCP was analysed thanks to a rheometry protocol in order to quantify the phenomenon. Later on, a parametric study was undertaken using this methodology. The operating conditions such as temperature and mixing process were studied as well as the effect of PCP structural parameters and the chemical characteristics of cement. In order to understand the origin of the phenomenon, adsorption measurements of PCP on cement particles were performed in the same conditions as those in the rheological measurements. Indeed, the phenomenon of "over-fluidification" could be related to the rate of the initial adsorption and the adsorption kinetics, both of which depend on the parameters of the process, the PCP structure and the cement reactivity.
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