Efflorescence Discolors Memorial Wall
Question:
We built a veterans’ memorial last year and used a color additive in the concrete. Since our dedication ceremony, the color appears to have leached out, leaving a whitish limestone-like appearance. I have attached pictures to give you an idea of what we are up against.
Answer:
This is a classic case of efflorescence – calcium-based scale leaching to the surface of the concrete. This is a natural process and occurs in all concrete. (See my blog entry “Efflorescence on Black Concrete” to learn more about how and why efflorescence occurs, as well as how to eliminate it.)
In regard to this particular case, the best way to proceed is to clean away the efflorescence and seal the concrete. Cleaning can be accomplished with a very dilute acid (40 parts water to 1 part muriatic acid) or even better, a non-acidic efflorescence remover. (Check out Prosoco for more information on these types of cleaners.)
No matter the cleaning chemicals used, apply the solution directly to the affected area and scrub lightly to loosen the white salt residue. Rinse the area with clean water. Let the surface dry thoroughly, then seal. I recommend using an impregnating waterproofing sealer to stop the movement of salts to the surface. It can be any type of silane, siloxane or silicanate, available at most concrete material or stone distribution centers. If you want to darken the concrete color or give it a glossy appearance, apply a low-solids acrylic sealer as a final coat. The most important step with this project is to seal the concrete once the surface is clean and dry. If no sealer is used, the efflorescence will reoccur and in six months the wall will look white again.
In closing, thanks to you and all your members for their service to country and community!
We built a veterans’ memorial last year and used a color additive in the concrete. Since our dedication ceremony, the color appears to have leached out, leaving a whitish limestone-like appearance. I have attached pictures to give you an idea of what we are up against.
Answer:
This is a classic case of efflorescence – calcium-based scale leaching to the surface of the concrete. This is a natural process and occurs in all concrete. (See my blog entry “Efflorescence on Black Concrete” to learn more about how and why efflorescence occurs, as well as how to eliminate it.)
In regard to this particular case, the best way to proceed is to clean away the efflorescence and seal the concrete. Cleaning can be accomplished with a very dilute acid (40 parts water to 1 part muriatic acid) or even better, a non-acidic efflorescence remover. (Check out Prosoco for more information on these types of cleaners.)
No matter the cleaning chemicals used, apply the solution directly to the affected area and scrub lightly to loosen the white salt residue. Rinse the area with clean water. Let the surface dry thoroughly, then seal. I recommend using an impregnating waterproofing sealer to stop the movement of salts to the surface. It can be any type of silane, siloxane or silicanate, available at most concrete material or stone distribution centers. If you want to darken the concrete color or give it a glossy appearance, apply a low-solids acrylic sealer as a final coat. The most important step with this project is to seal the concrete once the surface is clean and dry. If no sealer is used, the efflorescence will reoccur and in six months the wall will look white again.
In closing, thanks to you and all your members for their service to country and community!
A classic example of efflorescence, and the whitish discoloration it can cause.
posted by Chris Sullivan
at
11:28 AM
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