Rheological Behavior of Fresh Cement Pastes: Interaction between Superplasticizer and Viscosity-Enhancing Admixture

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Title: Rheological Behavior of Fresh Cement Pastes: Interaction between Superplasticizer and Viscosity-Enhancing Admixture

Author(s): L. D'Aloia Schwartzentruber and J. Cordin

Publication: Special Publication

Volume: 239

Issue:

Appears on pages(s): 409-422

Keywords: cement paste; interaction; mix design; rheological behavior; self-compacting concrete; superplasticizer; viscosity-enhancing admixture

Date: 10/1/2006

Abstract:
Self-compacting concrete (SCC) has high flowability and can be placed without vibration. It is defined as concrete that exhibits high deformability and good resistance to segregation. This kind of concrete is of great interest and has gained wide use especially in the case of structures that presents difficult casting conditions, such as heavily reinforced sections. From a rheological point of view, the use of a viscosity-enhancing admixture (VEA) along with an adequate superplasticizer (SP) content can ensure high deformability and stability. However, little is known about the interactions between SP and VEA. Hence, a study on several cement pastes formulated from the original paste of a typical SCC is proposed. One of the major aims of this paper is to show that empirical tests, such as spread and flow time, are suitable to characterize the rheological behavior of cement paste instead of more complex ones. Rheological properties, i.e. viscosity and shear yield stress can be well correlated with empirical test results in the range of flowable mixtures. Moreover, the experimental program leads to emphasize the effects of the mixing procedure and especially the introduction of the SP on the rhelogical properties of cement paste. Finally, test results enable to underline the interactions between SP and VEA used in designing SCC. VEA affects both viscosity and shear yield stress. However, its effect depends on the SP dosage.