Concrete Overlay Ingredients

Epoxy Coats

• Some decorative concrete overlays make use of epoxy resins, which consist of polymers with epoxide groups. When these polymers are mixed with an amine hardener, the ensuing reaction crosslinks the polymers to make a rigid material. The epoxy overlays also contain one of a variety of pigments that lends it the desired color. Sometimes marble, quartz or granite chips, recycled glass and various other aggregates are incorporated as well. The epoxy coating is applied atop a primer, which improves adhesion between concrete and epoxy, and a sealer that makes the surface more water- and chemical-proof.

Micro Toppings

• Micro toppings are thin, cement-based layers that come pretinted or are colored by mixing them with the pigment of your choice. These toppings typically include cement, aggregate or crushed rock and organic polymers. The polymer acts as a kind of glue to stick the mixture to the concrete below and to lend it desirable properties including strength and flexibility. Often, the mixture contains other chemicals such as antifoaming, slow-drying, fast-drying or leveling additives.

Spray-Down and Skim

• Skim coats and spray-down overlays are just different varieties of micro toppings. The ingredients are similar, but the specific additives included vary, because spray-down and skim coats are designed to be applied in different ways; spray-down overlays are sprayed onto the surface, while skim coats are applied with a squeegee or trowel. Stamped overlays likewise contain aggregate, cement and a polymer, although they differ in that the additives they contain cause them to dry much more slowly so the craftsman has time to make an imprint on them.

Self-Leveling Overlays

• Self-leveling overlays are similar to micro toppings in that they too are mixtures of cement, fine-grained aggregate and various organic compounds, including superplasticizers to make the mixture more flexible, polymers to enhance its strength and adhesion properties, and shrinkage compensators to minimize the amount of shrinkage that occurs as the mixture hardens. One of the key differences is the behavior of the self-leveling overlay, which is designed to flow along the floor and self-level without need to trowel it flat.