ISSN: 0149-6123
Page Count: 6

The Strength and Microstructure of High-Strength Paste Containing Silica Fume
Langan, BW
Associate professor, University of Calgary, Alberta

Ward, MA
Associate professor, University of Calgary, Alberta

Li, Y
Research engineer, Powertech Labs, Inc., British Columbia

Abstract

This paper describes the effect of silica fume on the strength and microstructure of high-strength paste. The particular tests carried out included: compressive strength, pore structure (mercury porosimetry), calcium hydroxide content, evaporable and non-evaporable water contents, and X-ray diffraction.

Water-cementitious ratios of 0.33, 0.30, 0.27, and 0.24 were tested at the ages of 14, 28, and 90 days. Silica fume contents were 5 and 10% of the total cementitious content by weight.

Results have shown that at a W/C ratio of 0.24, the strength of the paste decreased at all three test ages as the silica fume content increased. The positive influence of silica fume on the strength of paste decreased as hydration increased. The addition of silica fume did not reduce the total porosity but did reduce the maximum continuous radius significantly. X-ray diffraction results indicated that 10% silica fume virtually eliminated the calcium hydroxide content. The amount of non-evaporable water was less than would be expected by the reduction in the cement cogent.

Keywords:
silica fume, strength paste, compressive strength, microstructure, calcium hydroxide content, degree of hydration

Paper ID: CCA10158J
DOI: 10.1520/CCA10158J
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