Color Hardener Fails to Adhere

By Chris Sullivan – ChemSystems, Inc.

Question:

A colored and textured concrete pool deck I placed a year ago is showing signs of surface failure. I used color hardener in conjunction with powdered antiquing release and seamless slate-patterned texturing skins. The entire surface was sealed with a solvent-based acrylic sealer. Only one section of the project is showing signs of failure, while all other areas are wearing well and look good. What is causing this and how can it be repaired? Rip out and replacement of the deck is not an option because of the swimming pool.

Answer:

The problem you are seeing is lack of adhesion between the color hardener and concrete. Color hardener is a dry cement-based powder that is cast on the concrete surface when it is still wet. The water from the concrete "wets out" the color hardener from below as it sits on concrete surface. Timing is everything. Applying the hardener when there is too much bleed water on the surface will wash out the color. Waiting too long, after most of the water evaporates and the concrete becomes too dry, will create a weak, thin layer of color.

The other key factor in successful color hardener application is proper floating. Once the color hardener has completely wet out it needs to be worked in with a float (preferably wood or resin) to become one with the concrete. Certain sections of this slab are showing signs that insufficient floating took place, with the color hardener coming off quite easily, in pieces ranging from penny to quarter size. The final piece of the puzzle came when the homeowner explained that the section with failures was poured late in the day, under poor light conditions, and was rushed. I suspect that lack of floating really caused this problem. Rushing the job and skipping a crucial step (floating color hardener into the surface) ruined what otherwise would have been a very nice problem-free pool deck.

The fix, unfortunately, will never look as good as what the original work would have looked like if it had been done properly. You will need to explain to the homeowner that the look will differ slightly, and the colors and texture may not match exactly. Since the color hardener is flaking off quite easily, high-pressure water or sandblasting can be used to remove all the loose color in the areas that are failing. Once all the loose color is gone, apply a stampable overlay in a matching color. The good news is that the original gray concrete surface is rough enough from the original application so that no additional surface preparation will be needed.

Apply the colored, stampable overlay at a thickness of ¼ inch, and use the same color release and texture skin originally used on the project. If necessary, use water- or alcohol-based stains over the entire slab or select areas to blend the new with the old once the overlay has cured. Once the overlay and color work is complete, the entire project (new and old) should be sealed. For more information on proper color hardener application and overlays, refer to the many references and how-to books available at The Concrete Network.

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