Discolored Concrete: Three Frequently Asked Questions

After all the blood, sweat, and tears that go into a concrete installation process, nothing could be quite as deflating as finding that concrete stained and discolored. If you would like to learn more about how to avoid this frustrating and incurable problem, read on. This article will provide helpful answers to three common questions about concrete discoloration.

What causes discolored concrete?

Discolored concrete is strongly correlated to the use of plastic sheeting as a curing method. As its name would imply, plastic sheet curing involves laying a thin piece of polyethylene over the surface of the wet concrete. This helps to prevent unwanted evaporation, thus lengthening the curing time, and resulting in a more durable result.

Problems ensue, however, when the sheet of plastic is not perfectly flat. Any bubbles or wrinkles in the surface will lead to a phenomenon often referred to as the greenhouse effect. Here water evaporates up into the bubbles, then runs back down the sides onto the surface. This increases the hydration of the surface in those areas. Elevated water levels on the top of the concrete tend to result in discolored patches.

How can discoloration be avoided?

Those who are determined to cure their concrete according to the plastic sheet method can avoid discolored patches only by taking pains to ensure that there are no unwanted wrinkles. Having a helper--or two--when unrolling the polyethylene sheet makes it a lot easier to spot such problem areas. By acting quickly, the sheet can generally be adjusted to eliminate unwanted air bubbles.

Likewise, the threat of discoloration can be avoided by utilizing a different curing method--one known as liquid membrane curing. Here a special chemical substance is applied to the concrete just after troweling has been finished. This substance acts as a flexible, water-tight covering, and is capable of retaining a moisture content as high as 95 percent. Here the only concern is ensuring that the liquid membrane is applied evenly to the entire surface.

What other factors contribute to discoloration?

Bubbled sheeting is far and away the most frequent cause of discolored concrete. Yet other factors can also play into this annoying problem. To a certain degree, the shade of a batch of concrete can be affected by the alkali content in the cement. This has to do with the formation of color-related substances like alkali carbonates and chlorides. Uniform results can still be achieved, however, by ensuring that a particular batch of concrete is thoroughly and uniformly mixed.

For more information, contact companies like Gann Asphalt & Concrete.