ABSTRACT
The properties of fresh concrete are primarily governed by the mixture proportioning criterion and the mixture ingredients. This chapter discusses the effect of condensed silica fume on the properties of fresh concrete. The fresh concrete incorporating condensed silica fume is generally darker gray in color than fresh conventional concrete. The water demand decreases at all dosages of silica fume because of the dispersing action of the plasticizers. The increased water demand of concrete incorporating condensed silica fume can be overcome with the use of water reducers and superplasticizers, and to a lesser degree by reducing the fine aggregate content of a mix. The dosage of an air-entraining admixture to produce a required volume of air in concrete increases markedly with increasing amounts of condensed silica fume. Concrete incorporating condensed silica fume shows reduced bleeding because of the change in its rheological properties.
