New concrete pour black stains?

Not sure. What does your concrete contractor have to say? Would most certainly give him / her a jingle. Where I live it is hot and we water down the concrete at least three times a day for at least one to two weeks during the curing process. Helps prevent cracking. Agree that the spots look like oil stains. Any trees in the area that are dropping anything that could cause this?

I would call your concrete company and ask them right away! Hopefully it is just part of the curing process but I would ask to be sure.

Wow, that looks really unusual. I agree with Naomie; I'd give the contractor a call and inquire and ask them to come take a look at the problem.

Here's an article you might read before contacting the contractor.

https://www.foundationarmor.com/articles/discolored-concrete/#:~:text=Discoloration%20on%20the%20surface%20of,or%20during%20the%20curing%20process.

you need to call whoever did the concrete work for you and have them come look at it- better than you trying to fix something you already paid for -here is some info that may help explain what happened

https://www.foundationarmor.com/articles/discolored-concrete/#:~:text=Discoloration%20on%20the%20surface%20of,or%20during%20the%20curing%20process.

Hello. That does look suspicious. I would suggest calling your contractor and seeing what explanation they have.

I've seen some odd pattern formations over the years, especially if there were temperature fluctuations. However, this is something beyond temperature in my experience. This looks more like a mix issue. I would contact the company who finished it and have them get in touch with the ready mix supplier.

Hello Sam,

Call back the Company that did the work for you and tell them you are unhappy and why. Say you want them to put it right!

I would call the company and ask them why these black spots formed. It does look like oil spots or something weird. I would definitely not touch it till they come out to look at it.

You need to contact the contractor that did the work. Here's a link with more information on this type of discoloration:

https://www.concreteconstruction.net/how-to/construction/discolored-concrete-flatwork-the-causes-and-how-to-minimize_o

Hi Sam, i hope this link helps you out,

https://www.foundationarmor.com/articles/discolored-concrete/#:~:text=Discoloration%20on%20the%20surface%20of,or%20during%20the%20curing%20process.

You need to call your contractor, looks like they skipped a curing step. When I had my driveway poured, while the concrete was still wet they added a curative that was white and it took out all the dark spots

Thank you everyone. I did speak to the contractor already. He minimized my concerns. He essentially said that it is drying at a different rate in those spots and will go away once the concrete fully cures and not to worry about it. I was skeptical which is why I posted here.

Here's an article that might help - https://www.foundationarmor.com/articles/discolored-concrete/#:~:text=Discoloration%20on%20the%20surface%20of,or%20during%20the%20curing%20process.

If you havent already, put a garden sprinkler on driveway and keep it wet. This may help even out the colour. As soon as the concrete gets hard, 24 hrs after pouring, the best thing is to keep it wet all the time for at least a week. This will help harden and cure, Concrete LOVES water......

Call whoever did the work and ask them. I am sure they have dealt with this before.

I would think that they would have left you with some care instructions to follow.

Where I live it is getting too cold at night for the concrete to cure properly.

Sam, that definitely is not normal cement. was the cement truck previously used to mix colored cement? looks like stain from a dirty mix. also, why is there white foot prints and markings on the cement also. maybe the company will stain the driveway a dark color (free of charge) ?

The white footprints and markings are from the dust caused by the cutting. It rained soon after cutting and the dust (which was not cleaned up) hardened into clumps. The contractor took a look at it again and not surprisingly insisted that this is normal and will go away once it fully cures. He told me that he placed a vapor barrier under that portion of the driveway and that is causing the concrete to dry/cure at a different rate. The second part of the driveway, poured several days later because of rainy weather, has a few of these spots but not nearly as many. Though it makes me wonder if the mix was at fault.

I too would call the folks who did the work and have them come back out.

I had my house floor poured and it could be the extender that they sometimes out into concrete. You can always paint the concrete.

Looks like mold.

Hi! I wouldn't do anything until the contractor comes back and looks at it. Good luck!

Just an update. Concrete has cured for 37 days. The spots remain. The contractor has not responded to my calls. Spoke to both a house inspector and and General contractor who indicated the spots are a result of calcium chloride used to accelerate the hardening. The each stated that the calcium chloride was not spread evenly or mixed into the concrete well and that the spots will not go away.

Here is a link to the article I found that supports this. https://www.ohioreadymix.com/whitepapers/CIP_Discoloration.pdf

As far as the contractor goes, I've paid him $15,000 on a $27,000 estimate for 3700 sq ft driveway. Approximately 1500 sq ft was 6 inches thick. There were numerous other issues with the pour that we complained about including 100s of leaves/pine needs in the finish (this despite me pointing it out during the pour and their response was you will not see those once we broom finish it), uneven and inconsistent finish, different shades of grey on each of the 3 sections that were poured on different days, rain damaged finish because of a tarp leak, a low spot causing a puddle about 5 feet in diameter, foot prints/equipment tracks when they came back the day after without letting the concrete harden to cut relief joints, and never came back to seal. Overall, sloppy, hasty, and sadly, lack of pride in their work. Some of the contractor's responses to our complaints were the following gems: "You won't see that", "that's not a puddle", and "it's not my fault".

I'm not sure if he will come back for the rest of his money. I should ask him to repour, but to be honest, I don't really want him to do anything else here.

Thanks to everyone for the responses.

i would for sure contact contractor about that .. that should not happened