Title: Production and Application of Silica Fume and Geosilica

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Publication: CIA

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Date: 2/13/2011

Abstract:
AS3582.3 “Condensed Silica Fume” (CSF) has been renamed “Amorphous Silica” for the revision currently under review, thus recognizing that there are materials other than silica fume that satisfy all the chemical and physical requirements in that standard. The New Zealand standard for silica fume encompasses material from the ferro-metals industry (CSF) and naturally occouring silica (Geosilica). In this paper the production methods for CSF and Geosilica are outlined to show how each industry provides a quality assured product. The physical and chemical properties of each product are outlined. Concrete properties, including compressive strength, chloride diffusion, resistivity, bleed and sulphate resistance are detailed. Differences between the performances of the two materials are related to their chemical and physical properties. It is shown that the products are equally suited to high strength concrete but CSF provides higher early age strength while Geosilica provides lower heat of hydration.