Exposed aggregate concrete refers to a type of decorative finish in which the cement paste on the surface is washed away to reveal the aggregates in the concrete.
|When the concrete gets hard enough, but not too hard, cement on the surface is washed and brushed away to expose the aggregates in the concrete mix.||Close-up of exposed aggregate when it's done. Notice the many different colors of stones. The concrete matrix around the stones has a brown tint thanks to tinted brown sealer.|
This is one of the oldest types of decorative concrete that is still widely used today on siewalks, driveways, patios, and porches. A few things have improved with it over the years such as integral coloring and better sealers.
There are three different methods for producing this finish:
The key to a quality finish is getting the cement on the surface to stay soft while everything underneath hardens. This is achieved by using a surface retarder. After the concrete is poured and smoothed out, a retarder is sprayed on the surface. A few to several hours later the cement is washed away with a hose or pressure washer.
Exposed aggregate is a fairly easy method of finishing concrete that anyone with concrete finishing experience can do. Aside from surface retarder, it reqiures no more than the basic finishing tools. There are a few other advantages: