Proper sealing is an essential component of exposed aggregate concrete maintenance. A quality sealer will greatly enhance the beauty of your concrete patio or deck. More importantly, the right sealer will also protect the porous surface from stains and weather-related damage. Here are some tips to keep in mind when you plan your sealing project.
Clean Before Sealing
If your exposed aggregate concrete has just dried, you may be able to skip the cleaning and go right to sealing, depending on the recommendations of your contractor or concrete supplier. However, if your concrete has gone unsealed for any length of time, you need to clean the entire surface thoroughly, as well as remove any unsightly stains. Several excellent proprietary cleaners are available on the market, but a simple solution of laundry detergent and water will be effective in many cases. Difficult stains may be removed with more aggressive agents, such as denatured alcohol, mineral spirits, and TSP (or TSP-substitute). Before resorting to such methods, check the compatibility of your specific aggregate composition with the cleaner in question.
Choose the Right Sealer
Acrylic, silicone, and urethane-based sealers are widely available. No matter the brand or the composition, your sealer should dry to a thick film, resist yellowing, accept additional coats in the future, and resist anticipated stains such as motor oil, food, and pool chemicals.
Once these conditions are met, consider the type of finish that will be most appropriate. While a glossy “wet-look” finish is desirable for many applications, it should be avoided when sealing an exposed aggregate concrete pool deck. A gloss finish will become slippery when wet, creating a potential poolside hazard.
The matter is complicated by the extensive variety of aggregates on the market. A particular sealer may take on entirely different surface qualities when applied to crushed glass aggregate than it would when applied to granite chip aggregate. Test your sealer on a small area of concrete, and take it back for a refund if you don’t get the advertised finish.
Apply Thick Coats and Reapply Every Two Years
Sealer application depends on the type of sealer used and the type of aggregate in the concrete. Material differences create huge variations in any sealer’s covering power. For example, an aggregate that's slightly more porous can double the quantity of sealer needed for the first coat. The good news is that once the surface has been sealed properly, subsequent applications will require much less sealer to maintain the finish.
Depending upon the surface texture and the consistency of the sealer, you might find yourself using anything from a short-nap roller to a mop-style applicator. The key is to choose an applicator that allows you to spread a thick coat. You’re looking to flood the sealer on the concrete so that it saturates the porous aggregate; being stingy will actually slow the absorption process, and increase the amount of sealer that you will have to buy. Remember to re-seal once every two years or so, and you’ll be sure to preserve the beauty and utility of your exposed aggregate concrete for ages!