How to Cure Concrete Mottling and Discoloration

Prevent most mottling and discoloration by not adding calcium chloride to dry cement. Minimize the use of high-alkali-content cement.

Use forms that are all made of the same material. Use the same form release agent in all forms.

Trowel all concrete the same way at the same time. Troweling and screeding affect the density and water content of a concrete surface. Concrete that is troweled too early may become "trowel burned" when metal particles from the trowel become embedded in the concrete and then corrode.

Wash discolored concrete repeatedly with hot water and a scrub brush. Dry washed concrete overnight and repeat as needed.

Wet discolored surfaces with water from a hose. Then pour on a 3-percent concentration of acetic acid. White vinegar is usually a 5-percent solution of acetic acid. Rinse the acetic acid off the concrete with a water hose after 15 minutes.

Put on rubber gloves. Mix 2 lb. of diammonium citrate with 1 gallon of water in a plastic bucket using a paint stirrer. Pour the solution on the dried surface of the discolored concrete.

Use water to dilute the white gel that forms after treating stained concrete with diammonium citrate. Scrub the diluted solution with a scrub brush and completely rinse off with a water hose after 15 minutes. Multiple treatments may be necessary.