Published on April 15th, 2013 | by Henri


New concrete patio looks blotchy

Q.    I had a new concrete patio poured last summer around my in-ground pool. While drying I noticed (and brought to the attention of the contractor) that the concrete looked spotted with dark and light grey colors mixed throughout the concrete surface. The contractor said it “takes time to dry”, and the patio would change to a more uniform color.

Unfortunately, even now the concrete looks blotchy with light and dark grey patches throughout the work. Is there anything I can do? I have heard that you can “color” concrete. Your suggestions and comments are most welcomed.

A.    Blotchiness in concrete can be caused by the use of flake calcium chloride in the mix but that is used in cold weather so it is unlikely to be what happened with your concrete deck. Another possibility is that the contractor laid a sheet of plastic over the newly poured concrete to retard dehydration.

Dark spots occur where the plastic was in contact with the concrete. But if the contractor used a curing compound, the cause of the blotchiness is harder to determine and only an experienced concrete engineer looking at it may be able to come up with an answer.

Concrete can be stained after an acid etch but that must be done by an experienced professional. Over time, the sun may help to lighten up the darker areas.

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