Significance of Silica Fume in Enhancing the Quality of Concrete

In the Refractories world three decades ago, very few people were acquainted to silica fume and its usage. After a few years, it was used as an additive to brick. When added to high Alumina brick, mullite was formed in the matrix of the brick on firing, giving the brick good volume stability, strength and chemical resistance. When used in basic brick, high hot strengths resulted, at least at 2700oF, which was about the limit of what could be tested. At the time it was only logical that silica fume would be used in brick not castables. Brick were used for all critical applications, no one would have considered using castables. In this paper we shall discuss the manufacturing, properties of silica fume and its effect on concrete after addition. Today’s refractory castables have gone beyond having “brick-like properties” to actually out performing brick in many applications. Silica fume has played a major role in this transformation.