Concrete Architectural Finish Options
Advanced Cast Stone in Fort Worth, TX
Myriad finishes are possible with architectural precast concrete details, ranging from smooth and fine grained to rough pebble-like textures. Some of the finishes and surface detailing are as-cast (which means right from the mold, with no further treatment) or achieved after de-molding by mechanical or chemical means.
Here are some of the options, according to the Architectural Precast Association:
Exposed aggregate. This finish is achieved by casting the concrete against a form surface that has been painted with retarder to slow the set of the concrete at the surface. After the form is removed, the retarded concrete is stripped away by sandblasting or with high-pressure water to reveal the beauty and texture of the underlying aggregate in its natural colors. Endless variations are possible, depending on the type of aggregate used and degree of exposure. (See Exposed Aggregate Reveals the True Beauty of Concrete.)
Tooled finish. This achieves surfaces closely resembling hand-tooled natural stone faces. It's produced by casting the concrete against a smooth or specially textured or patterned form, and then "hammering" or "fracturing" the surface mechanically after the forms are removed.
Dry-tamp cast stone finish. This produces a fine-grained surface texture, with no coarse aggregate exposed, that closely simulates natural building stone. It's achieved by "ramming" moist zero-slump concrete against a smooth form until densely compacted. This method virtually eliminates the possibility of small bug holes in the finish and is often used for small trim pieces such as sills and lintels.
Smooth as-cast. This is a simple, unadulterated finish that displays the natural beauty of concrete without trying to simulate any other building material. The concrete is placed against a smooth form and is left in its natural state after form removal.
Light sandblast. After removal from the form, the element is given a light sandblasting to remove some of the cement from the surface, resulting in a subtle sand-textured finish.
Acid-etch finish. Acid etching produces a surface closely resembling limestone, brownstone or sandstone. After the cast element is removed from the form, it's washed with an acid solution and scrubbed to remove the surface cement. With this method, the exposed sand retains more "sparkle" than with light sandblasting.
Colored. All of the finishes above can further be enhanced by the use of integral coloring, which involves adding pigments directly to the concrete mix before it's poured into the mold.
Find GFRC Mixes for Precast Concrete