Q.: What is microsilica--a cement or an admixture? Where can I get more information about it?
A.: "Microsilica" is another name for silica fume. Some people in the concrete industry believe that "microsilica" is a better and more descriptive term than "silica fume." The product comes off in the fumes of electric furnaces that produce ferrosilicon or silicon metal and thereby gets its name. However, by the time it is collected for sale to people such as those in the concrete industry it has become a very finely divided solid--microsilica. Much has been written about the use of silica fume as a pozzolanic admixture in concrete. You can find a good discussion in a 3-page article beginning on page 443 of our May 1982 issue.