High Strength and Concrete Binders Part A: Reactivity and Composition of Cement Pastes With and Without Condensed Silica Fume

Cement pastes of interest for high-strength concrete technology were investigated by high-resolution solid state magic angle spinning 29Si-nuclear-magnetic resonance in combination with thermal analysis. The study results confirmed that condensed silica fume is a very reactive pozzolan. The conversion rate of condensed silica fume to hydration products after 3 days curing was in fact higher than for the neat cement at the same age. After 3 days curing condensed silica fume reduced the degree of hydration of the cement in the blended cement pastes when compared with pastes without condensed silica fume. The effect was enhanced at later ages when the cement hydration process stopped while the pozzolanic reaction continued to near completion.