Activite pouzzolanique et action de remplissage d'une fumee de silice dans les matrices de beton de haute resistance

Abstract The water reducing effect of superplasticizer in mortars is increased by addition of silica fume. The initial hydration of calcium silicates is accelerated. Consequently the formation of portlandite is increased but its quantity decreases rapidly by a pouzzolanic reaction. The improvement of the mechanical strength cannot be explained by this reaction alone. The principal effect is due to the reduction of the water-cement ratio following upon the addition of silica fume and superplasticizer.