Placing concrete is both a physical and chemical process. While the physical placement and finishing of the concrete can be mechanically replicated, there are too many variables to accurately replicate the chemical process. What does this mean???
Color Matching the Sample Chip
Matching the sample chip is not like matching paint chips. There are just too many variables that are beyond the control of the contractor. Color matching cannot be reasonably expected. The concrete color manufacturers clearly state this in their promotional and technical materials. Disclaimers abound... yet, at least once a year, I am retained to represent a party involved in a dispute over the final color of decorative concrete.
Variables Beyond the Contractors Control
I am not going to get into the reason why each of the following items contributes to variations in color. The factors that can effect a project may change during the day. Transportation time may be short in the cool calm morning and longer in the hot breezy afternoon. Each on their own can contribute to color variations:
- temperature (moisture evaporation & set times)
- direct sunlight
- moisture content of concrete (mix water and moisture content of the ingredients, e.g. sand, rock, etc.)
- ready-mix transportation time (traffic)
- ready-mix batch size
- revolutions of the mixer
- batch of the raw materials (e.g. gray-ness of the raw cement powder)
- liquid vs. powdered coloring agents
- white vs. gray cement
- admixes (water reducers, plasticizers, decorative aggregates, etc.)
- minerals & chemicals in the mix water
- pressure during troweling
- curing compounds & methods utilized
Any concrete color sample, whether it be a factory supplied concrete sample or a printed color chip, should be a generalization of the color to be received. It is impossible to exactly match the color sample.
It is guaranteed that the coloration of the finished concrete will vary once installed on the site. The changing temperature during the day of concrete placement can effect the final color development. Concrete that was in the direct sun & later in the shade or vice-versa, will develop different colors than concrete that remained entirely in the sun or shade. Controlling the shade or sun is WAY BEYOND the control of the contractor.
Property owners, architects, landscape architects, general contractors or other specifiers need to understand, that though every attempt is made to remove the variables, there are variables beyond the contractor's control.
The only guarantee one should ever receive when signing a contract for the placement of colored concrete is:
a) It will harden,
b) it will crack
c) the color will vary from one area to another,
d) the color will not match the sample and
d) no one will steal it without making a lot of noise.
Damaging Effects of the Sun
The color of the concrete will lighten over time as it is exposed to UV radiation and normal wear. Concrete that receives less sunlight (against the house, under arbors, north side of an object or structure, under potted plants or bbq) will retain it's original color longer.
Though the outdoor umbrellas, interior carpets, fabrics and draperies in your home fade from the UV exposure, no one ever complains to the carpet installer about the sun damage. Yet, concrete contractors are supposed to offer such guarantees???
As the concrete continues to cure & harden the color will lighten. If you have any doubt about the final color you will receive, it is a safe bet to select a darker shade. In a few months or years it will be exactly what you want.
Contractors need to manage the clients expectations. They need to sit down with them & explain that there may be significant color variations throughout the project. These are normal and to be expected. Color variations on their own are not considered construction defects. Even small mock-up samples will vary from the final colors.
The contractor needs to have the responsible party sign a disclaimer against matching any color samples - there are NO guarantees on color matching, color consistency or color variations.
Though there are millions of colored concrete projects in existence, a large number of them result in disagreements over the final color. Disagreement can be avoided if the parties had reached that conclusion prior to the placement of the concrete. And a signed disclaimer prevents anyone from ever saying, "no one ever told me" or "he never said that."
...just manage their expectations!
Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool and Spa