The concrete is flaking off fairly consistently and underneath is a rust color. It almost looks like nails have been embedded into the concrete because of the consistent circular shapes and the rust but its possible to wipe the rust away. I’m looking for the best explanation for what is happening here and the cause. This is in Canada so is this caused by the freezing/thawing or was there also a problem with the concrete from the start? Any feedback is appreciated.
Maybe some type of contamination of the concrete aggregate or sand
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It is hard to see from images, but it appears that the concrete was painted smooth.
With the wrong paint that does not breathe, that will make concrete crumble as it absorbs moisture and needs to have passive air flow to dry out. The aggregate may have contained some metal in it as well which may have rusted.
Did you probe it at all with a pick or screwdriver to see how much it crumbled? or to see if nails or pins were in place at each blowout?
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Yes, some old basement walls that I’ve seen appeared like they had too much sand and/or chunks or additional contaminates in the pour mix and spalled liked that.
The science of mixing together concrete for different purposes has become an art form over the years.
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I would report, Concrete pitting. Concrete pitting is the formation of small pits or indentations on the surface of concrete. Not only can pitting concrete be unsightly, it also poses risks if left unrepaired.
Moisture related problem.
Don’t paint foundation wall concrete!
Recommend a licensed poured concrete installation and repair contractor, provide a foundation moisture and weep tiles analyse. Make any required repairs within 1 year. Act upon/follow any recommendations therein.
First off, please post pictures individually instead of in a collage. Makes it hard to get a clear image when zoomed in.
Secondly, questions:
- I know you said you are in Canada, but where specifically?
- When was the home built? Year and time of year.
- Was this the only location in the home with the problem?
- Did you peel off any of the flakes to look at the backside?
- Was that a patch by the floor? (picture with wood paneling)
- Was this an exterior wall?
There are literally 100 reasons that could cause something like this… The only thing I can see is that plywood forms were used when concrete was placed, there is flaking/spalling, one picture shows an area with what appears to be popcorn (unconsolidated concrete), and it was painted with an unknown product. Since we were not there, details and better pictures are needed.
Randy is spot on. This is an aggregate issue. High ferrous iron content in that aggregate is causing a reaction with moisture and subsequent spalling.
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John, thats interesting- high ferrous iron content theory. Because then, I guess the iron content would be causing the rusting, that swells and causes the spalling or popping of the small areas seen? When I zoom in on some of the pics I automatically assumed there was some type of metal (wire mesh, nails, rebar) too close to the edge of the concrete and with moisture of it being to close to surface / edge it rusted causing swelling that caused the popping of exterior surface areas. Am I not seeing actual metal materials at popped out areas?
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No, you are not seeing metal. At least I’m not. You are likely seeing rust from the aggregate in the concrete. It’s a chemical reaction. Not really related, but think of Iron Ochre. It is also a chemical reaction from iron in the soil mixing with oxygen forming iron hydroxide (slime). It’s all chemistry.
The rust would not be my concern. The impervious paint coating, which is unsuccessfully attempting to mitigate a moisture intrusion issue, is likely the culprit as it holds water behind the surface coating. Water always wins in these instances.
I see this often in damp areas such as bathrooms etc. It can be wiped away with a damp paper towel. Rust stains are typically more permanent.
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