The Effects of a New High-Range Water-Reducing Agent on the Improvement of Rheological Properties

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Title: The Effects of a New High-Range Water-Reducing Agent on the Improvement of Rheological Properties

Author(s): T. Sugamata, T. Sugiyama, and A. Ohta

Publication: Special Publication

Volume: 217

Issue:

Appears on pages(s): 343-360

Keywords: high-range water-reducing agent; hysteresis loop; superplasticizer; thixotropy; ultra high-strength concrete; viscosity reducing effect

Date: 9/1/2003

Abstract:
Recently, ultra high-strength concrete with a specified concrete strength of 100 N/mm2 or more is being applied in Japan. The use of ultra high-strength concrete in the lower stories of high-rise buildings allows the architects to reduce the sectional area of support columns and thus increase floor areas. Other advantages are the suppression of cracking caused by earthquakes, and the increased durability of the concrete structure. In Japan, these ultra high-strength concretes are placed to congested reinforcement point. So, they are required to have high deformability and low viscosity. To produce this kind of concrete having an Fc of 100 N/nun2 or more, the water-cement ratio must be below 25%. Conventional BNS-based high-range water-reducing agents cannot impart high deformability and low viscosity until placement is finished to concrete with low water-cement ratio. Conventional polycarboxylate-based high-range waterreducing agents make the fresh concrete very deformable; however, the viscosity of the concrete increases, resulting in high loads when pumping and subsequent poor placing ability. It is clear that a new high-range water-reducing agent that imparts high deformability and low viscosity to the concrete is needed. A newly developed high-range water-reducing agent (SPN) imparts high deformability and low viscosity to the concrete until placement is finished. The authors compared the viscosity reducing effects of SPN and conventional polycarboxylatebased high-range water-reducing agent in concrete.