Cement overlays
We ground this concrete, at a retail store in Buffalo Grove, Illinois, clean, and resurfaced it with a white cement overlay. The store floor was covered with 1/4" of yellow carpet glue, and 1/8” of black "cutback" tile adhesive.
Often, because of age, abuse, cracking, or adhesives from previous floor coverings, such as carpet, tile or hardwood, an existing concrete slab cannot be properly, and effectively, stained. In such instances, thin, polymer-modified cement overlays can be installed to provide a brand new concrete surface to work with. At depths as shallow as 1/8", these cement - sometimes called “concrete” - overlays are extremely durable, and permanent, and allow for great creativity in patterning and coloring. Because of their modification with polymer, cement overlays also have great adhesion to concrete, and installed properly, they will not crumble, break apart, or delaminate.
Polymer-modified cement overlays, including "micro-toppings" and "spray-texture", can be applied with a hopper gun attached to an electric or gas-powered air compressor.
Cement overlays normally come in white and gray, and may be stained as such, after installation, or they may be integrally colored during installation, and then stained, to provide a unique, customized color pattern that may not be achieved through the use of concrete stain alone. Cement overlays may also subsequently be topped with another type of thin cement overlay, called a "micro topping", which allows the first overlay to show through, slightly, to the surface. This overlay “system” generally provides a more varied color effect than the use of a single overlay by itself. Lastly, cement overlays may be stenciled, or stamped, during placement to impart pattern and texture, in addition to color.
There are several techniques for applying decorative concrete overlays. Some overlays are troweled on top of the concrete slab. This is the most common type. Other overlays are self-leveling, meaning they are poured out on to the concrete, and then spread to a uniform depth. Finally, some cement overlays are rolled on with a paint roller or spray applied with a hopper gun. The type of overlay used typically depends on the durability required by the project environment, as well as the overall look being sought. For example, trowel-grade overlays generally exhibit greater color mottling, or "antiquing", through the use of concrete stain, than do self-leveling ones, whereas self-leveling overlays provide greater uniformity in color, something which is commonly referred to as a (gray) "warehouse look". All overlays, regardless of application method, require some type of mechanical surface preparation beforehand to ensure proper adhesion.
Integrally-colored, "spray-texture" concrete overlays create a perfect decorative finish on plain gray outdoor pool decks. Spray texture overlays look great, have ideal slip-resistance and are easy to clean and maintain.
As a general rule, the best look from decorative concrete overlays comes through acid-staining. Acid-staining brings out the variation in the texture and finish of the overlay, and does so in a natural-looking way. Concrete dyes and water-based stains are great for achieving a specific color with overlays, but tend to show the artificial, circular spray patterns that were used to apply them. Concrete dyes and water-based stains also exhibit penetration and adhesion difficulties due to the increased density found with cement overlays. For further information about the resurfacing of existing concrete, check out our popular, in-depth article, "The Expanding Role of Self-Leveling Overlays in Decorative Concrete", in the What's New section of this website.