Multiple discolorations in newly poured concrete slab

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We undertook one of our first home improvement projects this past weekend and had our small, builder placed back patio slabs demo'ed and had 2 new, larger concrete slabs poured this past Saturday. It's now Wednesday and one of the slabs (the larger one) looks fine while the other, smaller slab (pictured) is showing various discolorations and surface differences.

The other slab and area outside of the box all look uniform; grey with white speckles (which we understand will fade and even over time).

The area of concern is in the boxed area, where there's areas of black discoloration in some parts, while another piece of this slab looks bleached white compared to all the rest of the concrete work. It also seems to have a different surface consistency than the rest of the concrete.

I've read about treatments that can help with discoloration, but since there seems to be various discolorations going on, not sure the right approach.

Given we're newies at concrete work and the contractor has been of little help, we're reading all sorts of information online. Did a search but didn't see anything that speaks to treating one area with multiple discolorations/surface variations going on.

Should this be treated or will it even out over time? If treated, what would be recommended; vinegar, muratic acid or a commercial treatment of some kind? Would it work for both the black spots and bleached looking area?

Many thanks to anyone that has advice or expertise they could share.

q multiple discolorations in newly poured concrete slab
  8 answers
  • Janet Pizaro Janet Pizaro on Aug 16, 2017
    sorry but really you need to get in touch with someone over the contractor to state your complaint.Really they will be the only people to help you. If no satisfaction is given all the better business bureau and make a formal complaint

  • Smokinjoe2017 Smokinjoe2017 on Aug 16, 2017
    Thanks Janet. Before we move to that stage, we're hoping to get some advice on what part of this may be normal (given that it's relatively fresh) or possibly someone who's seen this before and can recommend a treatment. If all else fails after some fair attempts, we'll definitely plan to go to the BBB or small claims court.

  • C. D. Scallan C. D. Scallan on Aug 16, 2017
    It looks as though the discoloration is in the shade . Does it get any sun? Because it's been my experience that can make a difference in the coloration .

  • Leave it alone! Plus your "after care" instructions should have included hosing the surface down at least once a day for the first week or more so that the concrete cures slowly so that it does not develop surface cracks and dries evenly. It can take 30 days - sometimes more - to completely "cure."

  • Sharon Sharon on Aug 16, 2017
    I've always been told concrete doesn't fully cure for 28 days, so I wouldn't add any chemicals or cleaners to it until its fully cured.
    If he is a licensed contractor and refuses to respond contact your state contractor's licensing board online and file a complaint, but I think its too soon, I would call and ask what to do to lessen the discoloration, like should you be wetting it? so it cures evenly.

  • Cindy Cindy on Aug 16, 2017
    I agree with above comments. I don't think it is fully cured yet. Definitely don't add any thing to it. That may null the agreement you had with the contractor. Keep documenting and taking pictures in case you do end up in court. But my advice for now is to wait.

  • Cin21825342 Cin21825342 on Aug 17, 2017
    Concrete that large takes a long time to cure. Be patient. Wait a full month before being too concerned about the color. If it is still looking poorly call your contractor.

  • Travis Travis on Aug 17, 2017
    Ird not fully cured . However you need to contact the ready mix company and they will send out a rep. Good luck .