Planning to build a concrete bridge deck or parking structure? You might consider specifying silica fume — a by-product of silicon and ferro-silicon metal production — as a strengthening component in the concrete. The Lovettsville, Va.-based Silica Fume Association has published a users manual describing the best practices for using the material in concrete production. The free manual, which is available in a soft-cover edition or on a CD-ROM, covers proportioning, handling, placing, finishing and curing silica-fume concrete. It also discusses the health concerns of working with silica fume. To order a copy, visit www.silicafume.org.