Q.: Are special techniques needed to finish steel-fiber-reinforced concrete to prevent fibers from protruding from the surface?

A.: Although most conventional equipment can be used to finish concrete with steel-fiber reinforcement, some different techniques are needed to get the best possible results, according to ACI 544, "Guide for Specifying, Proportioning, Mixing, Placing, and Finishing Steel Fiber Reinforced Concrete." Flat, formed surfaces typically do not need special attention since they do not show fibers and are smooth after the forms are stripped. Chamfers and rounds at form edges and corners will keep fibers from protruding in these areas.

Slab surfaces usually require more attention. To provide added compaction and bury surface fibers, use a vibrating screed to strike off the concrete. A jitterbug can be used in areas where a screed is not practical, but be careful not to overwork the surface. Use magnesium floats to close the surface; wood floats can cause tearing. When using floats and trowels on steel-fiber-reinforced slabs, keep the tools flat because their edges can cause fibers to spring out of the surface. Do not use burlap drags for texturing, since burlap tends to lift the fibers and tear the concrete surface.