SEALER SERIES Part 7: Preparing Surfaces for Sealer Application

By Chris Sullivan – ChemSystems, Inc.

A simple but often overlooked step in any sealer application is surface profile. When I use the term "surface profile" in regard to sealing, I am including all aspects of the surface at the time of sealer application. But the two heavy hitters are cleanliness and porosity. Overlooking either can cause even the best sealers to fail.

Clean means just that: clean! A surface that is to be sealed must be free of all dirt, dust and any other contamination that will come between the sealer and the surface. Just spending a little extra time cleaning can make all the difference in how well the sealer adheres. In some cases, a good broom or blower is all that is needed to remove loose dirt. More stubborn contaminants may require removal by scrubbing with soap and water followed by a clean water rinse or acid etching followed by neutralization. I also consider residue from stain and dyes, excess release powder and efflorescence as surface contamination. These types of dry contamination are most often the culprits when sealers fail due to a dirty or contaminated surface. Efflorescence and stain residue are especially nasty because their extreme pH levels can affect sealer chemistry. A sealer that exhibits white "curds" in the film or soft spots is often failing due to a surface pH imbalance.

Porosity refers to the concrete surface's ability to take in the sealer. If the sealer can't wet out there will be little or no adhesion and durability. A hand-troweled concrete surface is usually porous enough to accept a one-part sealer with a solids content lower then 30%. A machine-troweled concrete surface will usually require additional prep to open it enough to accept the same sealer. Typical methods for opening a very tight or dense surface include light sanding or acid etching. When dealing with higher-solids sealers (usually two-part polyurethanes and epoxies with solids in excess of 45%) opening the surface or diluting the first sealer coat is highly recommended. A simple water test (to see how well the water wets out the surface) is a great way to determine if the surface is ready to accept the sealer.

As with any sealer, always refer to the manufacturer's installation guidelines for specifics on surface preparation and proper application techniques.

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Chris Sullivan

Author Chris Sullivan, ConcreteNetwork.com technical expert and vice president of sales and marketing for ChemSystems Inc.

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