Exposed aggregate finishes aka “retarded concrete” have been around for many years.  Exposed aggregate finishes differ from hand-seeded finishes such as Intecrete^® in that exposed aggregate concrete “exposes” the integral fine and coarse aggregates in the concrete mix, whereas with Intecrete^® finishes, the exposed aggregate finish is created by a exposing a combination of the integral fine and coarse aggregates and select aggregates that are applied by hand.

In the old days, exposed aggregate finishes were accomplished by simply using a broom with water after the surface has set long enough to prevent removal of a predetermined amount of surface aggregates.  Today, the process of exposing integral fine and coarse aggregates has been made much simpler by the use of chemical surface retarders such as Topcast^®, Optimus^®, etc.  The depth of the surface etch is controlled by using a specific etch number.  The lower the etch number the lighter the etch.  For instance, a Topcast^® 03 finish is significantly lighter in etch than a Topcast^® 150 etch.