Effect of polycarboxylate admixture structure on cement paste rheology

• Main Authors: M. M. Alonso, M. Palacios, F. Puertas, A. G. de la Torre, M. A. G. Aranda
• Format: Article
• Language: English
• Published: Consejo Superior de Investigaciones Científicas 2007-06-01
• Series: Materiales de Construccion
• Subjects: portland cement; superplasticizers; rheology; addition; compatibility
• Online Access: http://materconstrucc.revistas.csic.es/index.php/materconstrucc/article/view/48
• ISSN: 0465-2746; 1988-3226

The purpose of the present study was to analyze the effect of the structural differences in four polycarboxylate and polyether admixtures on the rheological properties of cement pastes with different chemical and mineralogical compositions and different active additions (CEM I 42.5 R, CEM I 52.5 R, CEM I 52.5 N/SR, CEM II/AV 42.5R, CEM II/B-L 32.5 R, CEM III/B 32.5R, BL I 52.5R and CAC – European standard EN 197-1:2000). The results of the minislump test concurred with the variations observed in the values of the rheological parameters (shear stress and plastic viscosity). The structural characteristic of the admixtures found to play the most prominent role in their fluidizing effect was the proportion of carboxylate (CG) and polyether (EG) group components. In cements characteristics such as fineness and the C3A/calcium sulphate and C3S/C3A ratios were also observed to be essential to admixture effectiveness. In this regard, the rheological parameters varied most widely in CEM I 52.5N/SR pastes and least in BL I 52.5R cement pastes. Of the additioned cements, the CEM III/B 32.5R pastes, which contained granulated blast furnace slag, showed the highest rises in flowability. Finally, the fluidizing effect of polycarboxylate superplasticizers was much more intense in calcium aluminate cements, although flowability declined rapidly in this material.