We're working on a job requiring epoxy injection of architectural concrete. The specifications require visual approval from the architect. We're concerned that removing the capping material will mar the appearance of the concrete. What type of capping material is easiest to remove? How should we remove it?
Peter Emmons, president of Structural Preservation Systems, says that you can use an epoxy capping material, but that you should burn rather than grind it off. Remove any remaining discoloration with a wet sandblaster. Bob Gaul, president of Construction Polymer Technologies, suggests two alternatives to an epoxy capping material: hot wax or cementitious capping material. Hot wax can be removed from flat surfaces with a putty knife. Light sandblasting or rubbing with an abrasive cloth may be necessary to remove any glossy look left behind. Hot wax must be applied to dry concrete and should not be used for injection pressures more than about 80 psi. Prepackaged, fast-setting, cementitious mortars that are commonly used for thin patches also may work. Trowel the mortar into and around the crack, wait for it to set, then inject the epoxy. Afterwards, the mortar outside the crack can be removed with sandpaper. Since some mortar is left in the crack, consider coloring the mortar to match the concrete. When using cementitious capping material, injection pressure also is limited to about 80 psi.