Concrete Admixtures
and Integral Color
Here's how five common admixtures -- air entrainers, plasticizers, accelerators, water repellents and pozzolans - affect color in a concrete mix.
by John Strieder

Water is the most harmless substance in the world. It won't stain clothes, car seats or upholstery. But it will play havoc with a batch of colored concrete.

When integrally colored concrete looks faded, H2O is the prime suspect, says Nick Paris, vice president of marketing for Davis Colors. The more water in a mix, the less intense the tint, he says. "Too much water is just the devil for decorative concrete. That's a common theme we get in most of our complaint calls."

Less water per unit of cement means richer, deeper and darker color, agrees Chris Forgey, marketing manager with the residential segment of Grace Construction Products.

Most contractors know better than to pitch bucketfuls of water into a half-poured batch of concrete, and if they don't, they learn fast.

Using admixtures that change the water-to-cement ratio and other properties of concrete is, pardon the pun, more of a gray area.

Aside from an integral color admixture itself, only one type of admixture is going to have a significant effect — a calcium chloride accelerator, which can cause mottling. "In general, admixtures when used properly do not have an effect on the final color," Forgey says.

If a slab poured with varying amounts of admixture is blanketed with joint cuts, release agents, patterns and textures, the difference will be hard to make out. "If there are any inconsistencies in the color, you've kind of masked that," Forgey says. "Putting a border across a driveway breaks up what the eye sees."

Aside from how much a performance admixture will affect tint, the most important question is how. Let's take a closer look at five common types of additives.