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chitownIrish 07-09-2010 09:03 PM

Small holes forming in newly poured concrete
I just had a concrete patio poured and about two days later, after the first rain, small holes started appearing in the surface - pinhole size up to about 1/8 inch. By each hole is a dark streak. I thought at first that these were small pieces of dirt and I could wash them away, but the dark streak is a stain on the concrete. It looks like something is just below the surface of the concrete and it pops through the surface like a pimple, leaving the streak.

I'm beginning to wonder if they are small pieces of iron or steel, and are rusting out and breaking through the surface. Has anyone here ever seen anything like this?

Scuba_Dave 07-09-2010 10:11 PM

Where are you located ?
Weather conditions the day of the pour ?

Gary in WA 07-09-2010 10:28 PM

While you are waiting for our concrete experts to answer: http://www.todaysconcretetechnology....blowholes.html

Be safe, Gary

jomama45 07-10-2010 12:21 AM

It is somewhat hard to troubleshoot something like this over the web, but it sounds to me like foliage from surrounding trees or bushes...................:wink:

Gary in WA 07-10-2010 02:24 PM

A few times after a slab pour, I have had the rust stains appear. Once it was from the wire (fence type- 2" x 4") reinforcing steel bleeding and rising with the air bubbles from working the water on top. Did they install any steel rebar or ? A few times I could not figure out where the stains came from..... I guessed it was steel (rusting) flaking off the mixing paddles at the concrete plant, though I never confirmed this. Or possibly oil from the truck/chutes delivering it? Impurities in the mixing drum from the water or insides of the mixer? Wait for more replies........

Be safe, Gary

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