Ready-mixed silica-fume concrete is currently used in the United States on a regular basis. During 1986, approximately 350,000 cu yd (270,000 cu m) of silica-fume concrete were placed. The silica fume is used as a cement replacement material or as a performance-enhancing admixture. This paper reviews the practical aspects of working with silica fume in ready-mixed concrete, with emphasis on the use of silica fume in the performance-enhancement role. Availability of silica fume and of products containing silica fume is described first. The current lack of specifications for silica fume, admixtures containing silica fume, and concrete incorporating silica fume is examined. Aspects of concrete production including measuring, adding, mixing, using high-range water-reducing admixtures, and controlling concrete temperature are discussed. Transporting, placing, finishing, and curing are reviewed to determine how silica-fume concrete differs from conventional concrete in these areas. Finally, several specific considerations for using silica fume in concrete for bridge decks are discussed. Ready-mixed silica-fume concrete has been placed successfully in a wide variety of applications. The price for a successful placement is strict adherence to the fundamentals of good concrete practice.
Samenvatting