Asked on Dec 7, 2011

We just had sidewalks poured a week ago.

Paul MAmazing Improvements and GaragesFrye finish carpentry & handyman services


It is cold... between 30-40 degrees since. The walks were covered for the 1st 3 days by the contractor. When they took the blankets off we noticed a white substance has stained the walks. Almost looks like it seeped up as the concrete was drying. We hosed the walks down in hopes of this washing away...but it did not. Are we stuck with this wierd staining? Will it go away?
Concrete walk
7 answers
  • Bob and RodMan S
    on Dec 7, 2011

    Give your contractor a chance to evaluate and take care of the problem. Concrete goes through a "chemical" process as it hardens and cures - it does not "dry" as we think of paint drying. Typically the freshly poured concrete is kept wet or damp as it hardens since the water is actually incorperated into the material as it hardens. If your sidewalk was covered unevenly with damp blankets the surface could reflect the differences in hydration in the blotched pattern illustrated. An on site review by your contractor or another concrete professional should determine if a surface cleaning with one of the standard concrete cleaners will take care of the problem without other damage

  • Harold M
    on Dec 7, 2011

    If it was freezing when he poured it, did they add calcium? Thats an old trick we used to use in upstate New York to keep it from freezing during curing. Of course we were pouring footers not sidewalks. I'd probably wait and see if it comes off after curing

  • Stephanie B
    on Dec 8, 2011

    I did call the contractor...he said he did add calcium. It was not freezing when he poured...maybe 45-50 degrees, of course cooler at night. He said the white marks happened because of the blankets he had to cover the concrete with? He wasn't willing to come and look or do anything about not really helpful in making me feel better. I am hoping it goes away like he seems to really looks worse then this pic even shows.

  • You should be fine that will wear off ,That's just the lime in the concrete,and an imprint of the blankets,Nothing to worry about,they look nice.

  • Paul M
    on Dec 8, 2011

    Over time the white marks will diminish or even go away completely. However you can speed up the process by cleaning with muriatic acid. Considering your temperature there and the fact that the concrete is new I would wait until spring to do it so you can let it weather a bit and cure some more as well. It takes several years for concrete to reach its full cure strength and when it is cold it takes even longer because the chemical reaction is slowed. When you weather begins to warm use some diluted acid and a stiff brush on a pole, douse it good and scrub a bit, then rinse thoroughly. It may take a few shots but it should come clean. If it doesn't you may want to consider using a concrete stain. Good luck!!!

  • Vinegar. Instead of muriatic acids. They are less aggressive and will allow the moisture to "vent" as it dries. There was another thread earlier this year and it came down to vinegar. Dampen the surface with water, apply the vinegar and allow to sit in the sun..... it will clear up. Good Luck!

  • Paul M
    on Dec 10, 2011

    Well that would probably work too. I have never tried it but vinegar is an acid as well although much milder. Most commercial professionals use muriatic acid but then again they are in a big hurry to get off the job too.

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