ABSTRACT
Abstract Agglomeration of silica fume causes the effective mean particle size of silica fume to vary between 1 and 50 J.lm, much larger than the 0.1 - 0.2 J.lm extensively quoted in the literature. The distribution and degree of agglomeration is dependent on source, bulk density and age. Ultrasonic dispersion can be used to indicate the dispersivity of silica fume. In practice undispersed agglomerates will always be present in mortars and concrete and under appropriate conditions may lead to alkali-aggregate reaction. It is hypothesised that the fusion of particles into chains is largely responsible for agglomerates that cannot be dispersed. Keywords: Concrete, dispersion, DSP, silica fume.
