Colored surfaces are much more visually stimulating than bland unadorned concrete. Depending on the project and your customer’s tastes, you can choose color combinations ranging from soft and subtle to bold and vibrant.
Use color charts as a guide
Most manufacturers of resurfacing materials, whether skim coats, self-leveling overlays, or spray-down toppings, provide an array of colors to choose from. Just as you would when selecting paint for a room, use the manufacturer’s color charts or chips to narrow down your options. Make sure the charts depict what the color will look like with the specific product you’re using. For example, some cement-based overlays are offered in gray or white base, with each offering a different level of intensity when colored.
Take advantage of precolored systems
Integral colors for toppings are usually achieved by mixing in dry or liquid pigments. But some systems come precolored so you don’t have to add the pigment yourself. The advantage of using these products is that you can be assured of color uniformity and accuracy without having to measure out the right amount of pigment. Manufacturers that offer precolored systems usually have a broad range of standard colors to choose from. Some even offer custom color matching.
Mix in your own pigment
Some overlay systems will require you to mix in the liquid or dry pigment yourself. To help you achieve color consistency and accuracy, manufacturers often simplify the dosing process by packaging their pigments in premeasured amounts. All you need to do is add the entire contents of the package to a bag or bucket of material to obtain the desired color. Other manufacturers may provide formulas for obtaining different degrees of color intensity, such as adding ¼ cup of pigment per bucket to produce a light tone or ¾ cup for a deeper richer hue.
When adding color, it’s best to mix the pigment into the liquid component of the overlay product (whether water or polymer) before mixing in the powdered component. First, measure the required amount of liquid into a bucket or other vessel. Then add your pigment in the precise quantity recommended by the manufacturer, and mix with a paddle mixer. Once the color is mixed in sufficiently, add the powdered overlay component and continue mixing. This will help to ensure a well-blended mixture free of clumps or streaks.
Straight iron-oxide pigments, both in liquid and especially in dry form, have a tendency to clump during mixing due to their large particle size. To avoid this, some manufacturers blend in a dispersing agent with a finely ground pigment that will dissolve more completely during the mixing process and achieve better color uniformity. These water-dispersible pigments can also be broadcast onto the freshly placed overlay and troweled to create a marbleized effect. To achieve even greater depth of color, consider using a combination of both methods, incorporating color into the base mix and then broadcasting a water-dispersible pigment onto the surface.
Experiment with topically applied color
Covering existing concrete with an overlay or skim coat lets you start with a fresh, clean canvas that is ideal for the application of topical colors, such as stains or dyes. These products aren’t entirely opaque, like paint. They have some transparency, which allows you to achieve interesting antiquing or marbleized effects. Or you can apply stains or dyes to integrally colored overlays to create layers of color.
Acid-based chemical stains are most commonly used to stain cementitious overlays. But newer water-based stains are gaining in popularity as a coloring method because they are easier to work with, leave virtually no residue on the surface, and come in an unlimited range of colors. When using water-based stains, you should test the surface first to determine whether it’s porous enough to allow the stain to penetrate, since these products will not chemically etch the surface like an acid stain. I have had good results sanding the overlay surface prior to water-based stain application using a rotary floor buffer and sanding screen.