Pursuance of Workability Retention by New Superplasticizer

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Title: Pursuance of Workability Retention by New Superplasticizer

Author(s): D. Hamada, K. Sagawa, Y. Tanisho, and H. Yamamuro

Publication: Special Publication

Volume: 262

Issue:

Appears on pages(s): 297-308

Keywords: adsorption; cement; ethylene oxide chain; hydrolysis polymer; hyper-branched polymer; plastic viscosity; rheology; superplasticizers; workability retention.

Date: 10/1/2009

Abstract:
Recently, concrete workability has become regarded as much more important because of large demands for high -strength concrete with high unit powder content and unstable quality of concrete materials. The new hyper-branched polymer was developed to provide better workability with much lower plastic viscosity of the mortar than the conventional polycarboxylate type superplasticizers. In this study, further workability improvement for a longer periods was investigated to provide better workability to the construction job site. The higher density of ethylene oxide (EO) chains adsorbed on cement surfaces was found to provide a more stable dispersion state that leads to lower viscosity of the dispersion system. However, the cement dispersion states might change with time generally due to the cement hydration process, so that the viscosity of the mortar or the concrete tends to become higher although the fluidity is maintainable. Thus, new additional EO chains were thought to be required with time on the hydrated cement surfaces to maintain a stable dispersion state. Based on this hypothesis, theoretically required EO chains were calculated and it was possible to maintain the mortar viscosity utilizing new hyper-branched polymer and hydrolysis type polymer.