I received a call from a homeowner who got a bid from a contractor to install a new stamped concrete walkway. The bid included integral color. When he looked at the samples, the colors looked “whitish” and not very vibrant. Is this what to expect from integral?, he asked.
There are differences between coloring systems, but common problems lie with each.
The colored concrete market is shifting toward integral color, especially liquid-dispensed systems. This isn't to suggest that shake-on colors will become a thing of the past; they won't. But it is no longer believed that shake-on color hardeners should be part of every stamped concrete job, even if the concrete is integrally colored underneath. It's easier for contractors to install integrally colored work. Fewer workers are needed, a well as less finishing steps, mess, and fears about the durability of stamped applications without dry shake hardeners. These fears turned out not to be true.
So how do you choose between the two options? It really depends on what you want.
The market for integral has always been larger than for shake-on color. This is partly because a portion of the integral color market is dedicated to nondecorative purposes, such as marking buried power or plumbing lines.
Integral color is composed almost entirely of metallic oxide pigments that resist UV radiation. Some manufacturers add water-reducing admixtures to their products, and liquid-dispensed color includes additives to hold the color in suspension.
One major advantage of liquid-dispensed color is the large variety of colors instantly available. Contractors can call a ready-mix producer and choose the color they want by its code number at the same time they order the concrete for a job. In the past, it could take a month for manufacturers to produce a special color and ship it to the contractor.
Integral colors provide very consistent color between truckloads of concrete, as long as all the ingredients, including water, remain the same.
Commonly referred to as dry shakes or color hardeners, shake-on colors are blends of portland cement, silica sand, and the same metallic oxide pigments found in integral colors. Sometimes they include water reducers to help them “wet out” better.
Shake-on color broadcast on fresh concrete can attain as much as 8000 psi. If you are using a 4000-psi concrete mix, shake-on color can add as much as 8000 psi to the surface. Strength isn't the issue, however; it's the high durability of the finish and increased impermeability of the surface.
Shake-on colors, unlike integral products, are not limited by the color of the portland cement, pozzolans, admixtures, and the fine aggregate in the concrete. With shake-on color, you can make the surface of the concrete a lighter shade than the base concrete.
The skill of the workforce is an important consideration. Workers must be able to broadcast color evenly for as far as 15 feet over freshly struck and bull-floated concrete. Having enough time to throw color and finish it under summer conditions is a skill too. In freeze/thaw climates, concrete is air entrained to provide durability.
But air entrainment reduces or eliminates bleed water available to wet up the color. It must be kept at the level required for durability in each region of the country. Contractors in freeze/thaw parts of the country must learn how to properly finish the concrete, because reducing air-entrainment levels to make finishing easier can result in scaling.
Unlike liquid-dispensed integral color, shake-on color is prepackaged and stocked with limited choices. Special color orders take more time to receive.
Which should you use?
As you can see, each color system has advantages and disadvantages. If you've never worked with shake-on colors, it's probably not a good idea to use them on your first project. However, it comes down to the particular requirements of a job and what specifiers want.