Manufacturing Process and Properties of Silica Fume and Its Application to Ultra-High-Strength Concrete

摘要

Silica fume is ultra fine spherical particles 0.1 to 0.2 (i,m in diameter consisting primarily of vitreous silica that was caught and gathered from dust in waste gases generated during manufacturing of various metals such as silicon, ferrosilicon and silicon alloys. Because large quantities of electric power are necessary to manufacture products such as silicon metal and ferrosilicon, they have been actively produced in countries with low-price power such as the Scandinavian countries, Canada and the US. In these countries attention has been focused on the application of by-product silica fume as an additive to concrete materials or as a replacement for cement. The utilization of silica fume in concrete started from research at the Norwegian Institute of Technology in 1950, and two years later concrete materials blended with 15 mass% silica fume to cement were used for the first time in the construction of a tunnel in Oslo City. In 1976 in Norway, silica fume was assessed as having value equal to slag as an additive and was recognized in the National Industrial Standard on cement to be mixed into cement at 10 mass % or less. In 1981 in Iceland it was standardized that the mixing ratio of silica fume was less than or equal to 7.5 mass% , On the other hand, in Japan where electric power was very expensive, silica fume was scarcely used as a concrete additive because metal silicon and ferrosilicon was only manufactured in very small quantities and consequently the amount of silica fume by-products was also small.