Q.: We're doing some remodeling of a hospital building that includes installing new floor coverings. The floor slab is a lightweight concrete placed over metal deck forms. Evidently when the concrete was placed, the top surface froze and was patched. Then it was covered with a rubber flooring. We're removing the flooring now and the patches are coming up with it. What products can be used to patch the floor again and make a longer-lasting patch?

A.: If you are putting down new rubber covering, tile, or carpeting, you could probably use a flowable topping that's either cement-based or gypsum-based. These are the underlayment materials that can be pumped into place and are nearly self-leveling. If any of the repaired floor won't be covered and will be exposed to hard-wheel traffic from carts, you might try a higher-strength flowable, cementitious underlayment or a polymer repair material. Contact one or more of the repair product manufacturers listed in Concrete Construction's Buyers' Guide (December 92) and ask for their recommendations. Remember to pay special attention to surface preparation when installing floor repairs.