Normal Concrete With The Surface Paste Removed
Many Types and Sizes of Aggregate Can Be Used
Exposed aggregate concrete is normal concrete from which the surface paste has been removed. This is accomplished by pouring fresh concrete, smoothing it, and applying a special chemical to its surface. This chemical prevents the surface paste from setting, while allowing the concrete underneath it to set up as normal. When the underlying concrete is hard enough (later that day or the next day), the surface paste is removed with a pressure washer and stiff brush. When the paste s removed, the gravel in the underlying concrete is left exposed. The surface is then washed with a mild acid solution to remove any residual cement dust. It is allowed to dry and is then usually sealed with a high gloss sealer. For a darker brown appearance, some contractors prefer to use a brown tinted sealer. Others prefer clear sealer to show the natural beauty and colors of the gravel aggregate. The aggregates used can be full sized gravel, pea gravel, or special aggregates seeded into the surface by hand before the concrete sets.
Another finish involves exposing only the sand. This is referred to as “exposed sand” or “sand matrix”.