Exposed aggregate concrete is a decorative concrete look that will enhance the curb appeal of driveways, pool decks, sidewalks and patios. It’s achieved when the top layer of concrete has been removed to expose the rocks underneath.
A properly applied sealer will keep this finish in pristine condition so the concrete doesn’t crumble or blemish over time. Sealers can be applied to new or existing surfaces and aren’t just pleasant to the eye. They can extend the life of the concrete by protecting the surface from harsh winter freeze-thaw cycles and hot 90-degree summer days. Sealers also can block ultra-violet rays that cause fading and inhibit the growth of mold and mildew.
Pick and choose
When it comes to sealing exposed aggregate, there are two types of concrete sealers that are most commonly used: penetrating and topical.
Penetrating sealers preserve the concrete without changing the look, allowing the exposed aggregate to retain its natural appearance and color. They seal the aggregate without leaving behind a visible surface film. On average they last from seven to 10 years and require little to no maintenance. Penetrating sealers won’t secure loose stones or prevent stones from coming loose. If you need to secure loose stones, an acrylic sealer is a better choice.
The second and most common choice is a topical acrylic concrete sealer which preserves the concrete and enhances it with a high-gloss finish often referred to as the “wet look.” Eight out of 10 of our customers choose a honey brown-tinted high-gloss sealer for their exposed aggregate surfaces. It provides a semi-transparent brown tint that helps to bring out the natural characteristics of the aggregate below.
The high-gloss coating is UV resistant and helps to reduce concrete dusting, staining, hot-tire pickup, mold, mildew and efflorescence. The brown tint allows for a uniform look that darkens the exposed surface.
Another benefit of using an acrylic sealer is that it’s topical. Instead of penetrating a 1/2 inch into the concrete, the sealer sits on top on the surface. It helps hold the aggregate pebbles in place, reduces pitting and extends the life of exposed aggregate concrete. Depending on weather and traffic, when using an acrylic sealer exposed aggregate concrete should be sealed every 12 to 36 months.
Clean and apply
Before applying either a penetrating or topical sealer, you must clean the exposed aggregate concrete. Pressure wash the dirt and grime off the surface, use rust remover to remove rust and a cleaner/degreaser to tackle tough oil spills. After the surface is cleaned, allow a day to dry.
Once the concrete is dry, begin the sealing process. Using a ½-inch roller and a pump-up sprayer, start applying the sealer. If the project is a driveway, start by the garage door entrance working toward the road making sure not to step in the sealer.
Apply sealer quickly to avoid any overlaps and roll marks. It’s best to work in smaller 4-by-4-foot sections. The sealer should be applied at the manufacturer’s spread rate. This is typically between 100 and 150 square feet per gallon.
Let the sealer dry for one to four hours for foot traffic and 24 to 48 hours for car traffic. If the sealer didn’t dry evenly, apply a second coat to even out the appearance.
Tyler Stephens is president of Stephens Concrete Sealing, a surface restoration, cleaning and sealing company in Indianapolis, Indiana. The family-owned company, founded in 2009, services both homeowners and businesses. Tyler can be reached at (317) 264-9781 or [email protected]