silica fume
Posted by Marianna on October 6, 2006
what effect does silica fume have on the color of concrete? does it lighten or darken the surface
Dear Marianna,
The ACI 234 committee which provides guidelines for the use of silica fume in concrete has the following to say about the effect of silica fume on the color of concrete. “Fresh and hardened concretes containing silica fume are generally darker than conventional concrete. This is particularly apparent for concretes containing higher percentages of silica fume as well as those silica fumes that have a high percentage of carbon. The color difference may lesson and virtually disappear after some time”.
Regular Portland cement concrete can also be darker in early ages and become lighter after a few days. Since silica fume hydrates as at a slower rate than cement the dark color lasts longer. However, as the silica fume hydrates the color of the concrete will become lighter. A damp or moist environment may take a little longer. If color is a major consideration you can use white silica fume. It is a little more expensive but does not darken the concrete.
Hope that answers your question.
