Sprayable overlays are inexpensive and can be applied to damaged concrete that is still structurally sound. Today more than 50 manufacturers produce sprayable polymer-cement materials, which perform equally well in freeze/thaw or hot climates.
Acrylic resins and ethyl vinyl acetates (EVA) dominate the industry. The latter also are called polyvinyl acetates (PVA). Acrylics dominate the two-part system market. EVAs are easier to work with. Both products can be mixed with integral color or left in their natural state.
Acrylic sealer is applied after the polymer cement is hard. Installers can color it with metallic oxide colors or place it as a clear coating.
A hopper-gun—a spray gun driven by low air pressure—is used to spray polymer cement on the concrete surface in splatters. The size of the splatter can be regulated by controls on the gun and by the liquidity of the mix.
In terms of problems that cause durability and liability issues, preparation is the key.
When sprayable overlays are placed on new concrete installations, a light broom finish is adequate. A base coat, can be applied with a squeegee or a trowel. The second coat, which is sprayed on, is referred to as the texture coat. The texture coat is "knocked down" with a trowel immediately after spraying.
Placing color in the sealer coating brings uniformity to a project. Clear sealers are used mostly when more than one color is present in the finish.
Knock-down finishes are still the most popular. But considering maintenance over time and managing problems, contractors say that a one-color finish with a colored sealer is the least problematic.
Like any cast-in-place concrete product, forming details, square footage, and intricacy of patterning and coloring influence price.