Concrete Curing Problem

Discussion in 'Hardscaping' started by JimLewis, Mar 26, 2008.

  1. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,876

    We don't install concrete ourselves. But if it's part of a larger landscaping job, we'll take on the work and sub the concrete finishing work out to a contractor we've worked with for years. And that's what happened last October. We subbed part of a large job out to our concrete flatwork contractor (who has always done excellent work in the past). But this time, the concrete patio he installed for our customers didn't turn out so well. Specifically, the patio has large sections that are blotchy. The overall patio is kind of a gray color with these large sections in the middle that are more white in color.

    It was apparent within a week or so of doing the job. And the homeowner questioned me about it. My contractor told me that since it was fall and the temperatures were fairly low, it would take a while to cure and once it all cured, it would all look the same. Okay, fine.

    Fast forward to today, and it looks pretty much the same as it did back then. Still very blotchy, still two distinctly different colors throughout the patio. I called him today and he tells me that some patios just take a lot longer to "cure out". He said this has happened to him before and eventually - after 6 months or a year it will all cure out and be the same color.

    I am no expert in concrete. That's why I sub this stuff out. But I've attached some photos. What do you guys think? It actually stands out more in person than it does in this photo from my cell phone. But you'll get the idea.

    One other thing, if you go to the gray areas and scratch at it a little bit with a screw driver or pocket knife or something, the gray part sorta comes off and leaves the white color. So that makes me think maybe I could just use some sort of buffing machine or something to get the top layer off. Do they make such a machine?

    Any suggestions? Comments?

  2. Edgewater

    Edgewater LawnSite Senior Member
    Messages: 457

    That can happen to concrete if it is poured in cold temps. It it is worked and not all of the water goes down, it will do that. I have a garage floor that was like that when poured almost 12 years ago (My dad's).

    The color is the least of the problems, those area will always give off dust. That part of the concrete is very weak, and every time it is swept, more and more comes off. It really annoys my dad and I. The only way to fix it is either grind to where it is properly cured (if it is at all), or break out and re-pour.

    Good luck
  3. AceFinish

    AceFinish LawnSite Member
    Messages: 98

    What it also could be as well is if you put water on fresh concrete that is hard and the sun hits and bakes it so to say that water will actually bleach the concrete. So maybe somebody spilled water on it.
  4. vaham

    vaham LawnSite Member
    Messages: 69

    It may or may not go away.... look into covering it with a white concrete curing compound. Although the purpose of curing compound is to harden the surface finish when applied right after finishing, it's too late for that aspect..... but the compound will still adhere and provide a more uniform color.

    Just an idea-

    I did that once on about 6000 lin. ft. of CG6 curb and 4' sidewalk that was placed by a developer who went bankrupt. Two years later, I inherited the job from my employer of getting the subdivision off of bond and into the VDOT road system. The white curing compound on the concrete curb and gutter and on the sidewalks sure covered a lot of sins and saved about 250K on break-and-replace.
  5. bullethead

    bullethead LawnSite Senior Member
    from Texas
    Messages: 273

    I am not a concrete expert either - but I almost think you could etch the patio with muriatic acid and it would remove all of the gray part. Start off with a light concentration and work your way up until it's just enough to remove it. If you go at it too hard, you will expose alot of aggregate.
  6. PatriotLandscape

    PatriotLandscape LawnSite Bronze Member
    from MA
    Messages: 1,209

    You could also apply a dark gray concrete stain if it starts getting out of hand with the customer. I hate these kinda calls.
  7. forestfireguy

    forestfireguy LawnSite Senior Member
    from nj
    Messages: 601

    Only problem with stain is it may not "take" the same in the already different areas.
  8. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,876

    We decided we're going to try a stain on it first and see how it comes out. If we (and the client) are not happy, we're going to do a concrete overlay. Which my concrete guy will charge be $1000.00 for. But I think the homeowners are going to split that with me. So that's good.

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