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Colored Concrete Q&A

The above picture shows how Pavers are much easier and to maintain and keep looking perfect. For those who insist on colored concrete, here are some frequent asked questions and yes we clean ‘n seal a lot of concrete as well.

Efflorescence occurs with all concrete and is the most frequent problem that concrete contractors face with colored concrete.

Efflorescence is caused when soluble salts and other water dispersible materials come to the surface of concrete and mortars. It’s induced by low temperatures, moist conditions, condensation, rain, dew, and water added to the surface of fresh concrete to assist troweling.

Any material containing portland cement results in efflorescence. The most usual reaction occurs when calcium hydroxide (lime) formed in the hydration reaction of portland cement (approximately 140 pounds per cubic yard of concrete) is transported by water to the surface through capillaries in the concrete.

Efflorescence is normally white and shows up more on darker colors than white or light gray because of the contrast. Only 0.2 ounce of calcium carbonate per square yard of surface is needed to cause a significant shift in color. Some forms are very difficult (if not impossible) to remove, while others are easy—especially if they are removed right after they form.

After acid washing, slabs should be rinsed thoroughly and neutralized with baking soda (sodium bicarbonate) or an equivalent. Acid residues can harm plants. The reaction products of acid on concrete are all soluble calcium and iron salts, which can cause more efflorescence.

When efflorescence can’t be removed with acid washes, other commercial products are available. One is ethylenediamine tetraacetic acid (EDTA), which rapidly dissolves calcium salts. EDTA will also damage concrete, so it’s best to test it on an inconspicuous sample area first