Q.: We constructed some white flatwork with 3/4-inch redwood separators between panels. The top 3/4 inch above the redwood was caulked. This white concrete adjoins an area of pattern-stamped dark gray concrete, so we were asked to use a black caulking material above the redwood on that side. The caulking material was self-leveling and in two places it ran downhill out of the joint onto the white concrete. We haven't been able to remove it with solvents. What do you suggest?
A.: Probably the most effective way would be to try to burn it off with an acetylene torch with a wing tip that produces a broad flame. Don't let the flame stay too long in one place and damage the concrete. Try to develop a light touch that is yet heavy enough to burn off the caulk. There may be some residual ash that may have to be brushed off with a stiff brush or broom.
If that proves unsatisfactory, we suggest asking the manufacturers of the caulking material for suggestions on how to remove their product and also asking the same question of various manufacturers of cleaners (see "Cleaning Materials" in the Buyers' Guide of our most recent December issue of CONCRETE CONSTRUCTION magazine). However, if you do find an effective solvent it will probably be necessary to use it in combination with white rags or cotton, weighted down and left on the concrete to absorb the caulk as the solvent evaporates. Otherwise the solvent might just carry any dissolved material more deeply into the concrete. It may take more than one application for the process to be effective.