We supply integrally colored concrete for decorative concrete flatwork in the area. Building owners often complain that the color of the in-place concrete doesn't match that on the color chip supplied by the coloring pigment manufacturer. We then get blamed for not supplying the right concrete. Are there any solutions to this problem?
There are two keys to solving the problem: realistic expectations by the owner and close cooperation between the producer and the decorative-concrete contractor. Decorative-concrete contractor Steve Smith, Crownsville, Md., says he tells his clients that the color chip represents a family of colors, and the owner shouldn't expect an exact replica of the chip color. Smith also says that applying two coats of sealer will darken the color, so it may be necessary to pick a lighter shade or add less pigment per cubic yard than the manufacturer recommends, knowing that the color will darken after sealing. For instance, a rose shade will look redder after the two sealer coats.
For your part, it's important to supply all of the concrete for an integral-color job from one plant. Cements from different sources can have a profound effect on final color, especially if they contain ground-granulated blast-furnace slag or pozzolans, says Smith. For color work, Smith prefers a straight portland cement concrete, with all the cement from the same silo at the same plant. Ordering concrete from different plants that use cement from the same manufacturer still may not guarantee a desired color match when cement manufacturers import clinker from different areas.
Smith says he took color chips from manufacturers, mounted them on a board, and applied two coats of the sealer he uses. He says these chips more faithfully reproduce the expected final in-place color for his customer.
Again, customers must understand that no two loads of concrete are exactly alike, and that some degree of color variation within a project is to be expected. And, as previously stated, the in-place color often won't perfectly match the chip color.