A Study of the Properties of Portland Cement Incorporating Silica Fume and Blast Furnace Slag

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Title: A Study of the Properties of Portland Cement Incorporating Silica Fume and Blast Furnace Slag

Author(s): S. NagatakiI and C. Wu

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 1051-1068

Keywords: alkali-aggregate reactions; blast furnace slag; blended cements; chemical analysis; compressive strength; drying shrinkage; porosity; hardened paste structure; mortars (material); particle size distribution; hydration; silica fume; sulfate attack; Materia

Date: 6/1/1995

Abstract:
The workability, strength, and durability of concrete are affected by particle distribution and chemical composition of cement. So, a cement which has ideal particle distribution and chemical composition is needed is needed for making high performance concrete. This kind of cement can be realized by blending portland cement, silica fume, and blast furnace slag, because they have different particle distributions and chemical compositions. In this paper, the triple blended cement was composed of 10 percent silica fume, 30 percent blast furnace slag, and 60 percent portland cement as it had suitable chemical composition and the densest particle distribution in portland cement or portland cement admixed by silica fume or blast furnace slag in this research. The hydration process of the triple blended cement was similar to the portland cement, but the heat of hydration and Ca(OH) 2 content in the hydrates were much lower than that for portland cement. It was found that the porosity of the hardened paste was so low that it was half of that in portland cement paste. The R 2O in its pore solution was only 88 percent of that in pore solution of portland cement paste. This fact means the triple blended cement may reduce the alkali-silica reaction of concrete. The flows of the fresh mortars made by the triple blended cement were higher or lower than the flow of the control mortar depending on the specific surface area of silica fume used. The compressive strengths of the mortar were higher than that of the control mortar as its denser paste. Because of the low Ca(OH) 2 content in the hydrates and R 2O in the pore solution, the resistance of the mortars to sulfate attack and alkali-silica reaction was high. However, the drying shrinkage of the mortars made with the triple blended cement was higher than that of the control mortar.