Untold thousands of finishes can be imparted to concrete surfaces through material grading and selection, surface finishing techniques in the case of concrete flatwork, the use of special forming materials or textured form liners, exposure of surface aggregates, numerous techniques for rendering and abrading hardened surfaces, and through the utilization of integral colors, dry shakes, and paints and stains. With thousands of aggregates to choose among, along with hundreds of shades and colors of cement, it follows that there is literally no outer limit to the range of possibilities. This article describes briefly some of the more familiar finishes, including as-cast, abraded surfaces, tooled surfaces, stamped concrete, external rendered finishes, colored concrete and aggregate exposed by other methods.
Surface aggregates can be exposed to various depths by the use of chemical retarders which prevent or delay the setting of cement paste near the surface. When the main body of the concrete has set, the retarded surface material can be washed or brushed away to expose the aggregate. Although the technique differs somewhat depending on whether or not the surface is molded against a form, equally good results can be obtained on both concrete walls and flatwork. Exposing aggregate by means of retardation is considerably less costly than tooling and other mechanical methods and it avoids the dulling of aggregate color which is likely to occur in mechanical fracturing and abrasive blasting.