Remove all dirt, wax, dust, mildew, and loose or scaling material with a scraper, wire brush or stiff bristle brush.* Grease, wax and oil should be removed by scrubbing with a heavy duty detergent in warm water. Rinse the surface thoroughly with clean water and allow it to dry. Using a pressure washer? Do not use on a pressure setting above 1750 psi, to avoid damaging the concrete. Remember, concrete acts like a sponge. Pressure washing and general cleaning may trap residual moisture in the concrete.
To check for trapped moisture, affix a 12” x 12” piece of 3 mil plastic or aluminum foil to the surface, taping it tightly along all four edges. Remove it after 24 hours. If the surface side of the plastic or foil is damp, allow additional drying and repeat the test.
If you see white, powdery, crystal-like deposits on the surface, they are naturally-occurring, water-soluble salt compounds in the masonry, pushed out by water intrusion. When the water evaporates, the salt residue remains. This effect is called efflorescence and, because it prevents DRYLOK® Protector Clear Low Sheen Penetrating Sealer from properly bonding to the surface, it must be removed. Treat it with DRYLOK® Etch®** (liquid or powder formula) or muriatic acid according to the manufacturer's directions, rinse the surface and allow it to dry.
DRYLOK® Etch® will also properly prepare the concrete’s profile to accept the coating. Properly prepared concrete should look and feel like medium grit sandpaper. If the concrete remains smooth, repeat the etching procedure. You can test the concrete porosity by sprinkling a few drops of water onto the surface in several areas. If the water is readily absorbed, you are ready to apply the coating. If it beads or sits on the surface, additional cleaning and etching is needed. Rinse thoroughly with clean water and allow the surface to dry for 24 hours.
Patch all holes and cracks with a suitable cement-based patching compound. Be sure to smooth the patch evenly. Allow the patched area to dry thoroughly.
