The use of microsillica as a pozzolan in concrete was originated in Scandinavia during the early 1950’s and introduced to the United States in 1984.  Micro-silica is a by-product from silicon carbide and metallic industries where it is recovered from exhausts of electric furnace.  It is approximately 100 times finer then Portland Cement.  When used in concrete, it acts as a filler, allows for thinner overlays and better physical properties including permeability and density.