On the compressive strength development of high-performance concrete and paste - effect of silica fume

The compressive strength development of sealed high-performance concrete and paste specimens, with and without silica fume, have been studied from 1 day and up to 4 years. The paste and concrete specimens were prepared in such a way that segregation was avoided and the silica fume became well dispersed. Under these conditions silica fume increased the strength of paste just as much as it increased the strength of concrete. It appears that the enhancing effect of silica fume on concrete strength is due to an improved strength of the paste phase as a whole, and not due to an improved bond strength between the paste phase and the aggregate particles, as has been suggested earlier. The concretes and the pastes with 10% silica fume appeared to loose strength over a period of time before the strength increased again.