Many city councils face decorating decisions when their city embarks on a downtown streetscape or similar project. One of the most common choices they make is using colored concrete to affordably jazz up plain gray concrete and public spaces.
To help cities make a good decision about colored concrete, we turned to two ARM members who are experts about this. They’ve seen city projects succeed and fail, and they know what works and doesn’t work to ensure your colored concrete looks great and lasts decades.
Here are four things they want you to know about colored concrete:
1. Choosing a color for concrete is NOT like choosing one for a bedroom wall.
The color pigment for concrete is mixed with natural elements like aggregates and portland cement. Crushed rock can range from pink, orange and tan to brown, dark green and gray. Portland cement can range from white to pinkish to dark gray. Your color is affected by those colors.
In contrast, when you choose a color for your wall, it’s consistent from gallon to gallon. It’s not like the black bristles of your brush add black to your Benjamin Moore paint.
Be sure to select your concrete color from a specific concrete color chart with specific names. Don’t refer to a paint company’s chart and names.
2. Make sure the colored concrete comes from the same ready mix concrete plant.
If your concrete comes from different plants for a single project, you could end up with one shade of charcoal concrete at Main and 1st Streets, and another shade at Main and 3rd!
It is not unusual for a contractor to tap into a few different ready mix producers to complete a project, but you can end up with inconsistent colors (even with plain gray) when the concrete dries. One plant might use pinkish portland cement and another plant dark gray, for instance.
Using the same plant also ensures that the water-to-cement ratio is consistent from concrete batch to batch. City inspectors should make sure the contractor doesn’t add additional water at the job site because it can change the color in a single batch.
3. Avoid reds, even though cities traditionally select it.
Red pigments interact with portland cement and aggregates in unpredictable ways due to the iron oxide that makes it red. Iron oxide also is a natural element. The color pigment, the aggregates, the cement, the iron oxide: the mix can be like four kids squabbling for dominance of the t.v.
No other concrete color is as fussy as red. Reds can turn to rust, brick, cherry, pink, and even orange, as one city recently discovered. If you still want to choose red, use it sparingly and choose a reddish-brown, like “Marshfield,” a Scofield color.
Another reason for avoiding reds is because cities often do not seal their colored concrete every two to three years to maintain them and fussy reds, especially, don’t hold up well.
By choosing not to regularly seal your colored concrete, the new Streetscape you celebrated at your Grand Opening could look quite different by your third downtown Octoberfest event. (call-out quote)
4. Choose contrasting colored concrete for the biggest impact and bang for your buck.
How about charcoal gray and tan with the traditional gray? The contrast can be very attractive, helpful to pedestrians and drivers, and as affordable as a single color.
Regular sealing, of course, will keep the contrast clear and bold over time.
Many thanks to ARM Associate Members Andy Pearson of SIKA®, an international chemical company, and Guy Peterson of Scofield, a division of SIKA® specializing in color pigments. They came up with these four points about colored concrete and know a great deal more.
Questions about colored concrete? Contact Guy Peterson of Scofield, who’s a walking encyclopedia about color pigments: firstname.lastname@example.org.