Influence of silica fume on the workability and the compressive strength of high-performance concretes

The workability and the compressive strength of silica fume concretes were investigated at low water-cementitious materials ratios with a naphthalene sulphonate superplasticizer. The results show that partial cement replacement up to 10% silica fume does not reduce the concrete workability. Moreover, the superplasticizer dosage depends on the cement characteristics (C(3)A and alkali sulfates content). At low water-cementitious materials ratios, slump loss with time is observed and increases with high replacement levels. Silica fume at replacement contents up to 20% produce higher compressive strengths than control concretes; nevertheless, the strength gain is less than 15%. In this paper, we propose a model to evaluate the compressive strength of silica fume concrete at any time. The model is related to the water-cementitious materials and silica-cement ratios. Taking into account the author's and other researchers experimental data, the accuracy of the proposed model is better than 5%. (C) 1998 Elsevier Science Ltd.