Surely this is mold. But on a bleached open concrete area?

Submitted by Moogy_C t3_125tsdy in DIY

After a month of humid and rainy conditions, I opened my garage up to this. It's only present on the open area of the ground. I removed what you see in the picture and bleached it, but it comes back in the same spot literally within 3 days (though not to this extent).

Is it somehow not mold? It has to be. How did it come back so quick? Why on this specific area? How do I get rid of it? Thank you for any help.

If anyone has some insight as to why I'm being downvoted, I'd appreciate that too. Is this post not appropriate? Is there a more relevant sub I should be postng to? Thank you.

edit again: I appreciate the responses, everyone. Looks like the consensus is efflorescence, as opposed to mold. Any further info is welcome as well. Thank you again.

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Hattix t1_je5um9m wrote

That's efflorescence. It means you have a moisture problem, not a mold one.

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Moogy_C OP t1_je5vb03 wrote

Ah, thank you, I'll start looking into it. Theoretically, better ventilation should prevent this from appearing then? There are no water sources other than rainy weather.

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Sluisifer t1_je60tsv wrote

What you see is salt. Water is in the concrete and there is salt dissolved in the water. When the water evaporates on the surface of the concrete, salt crystals remain.

More ventilation just means that the drying happens faster, but does not change the amount of water and salt that is in the concrete. So no, ventilation does not help. You need to prevent moisture from getting into the concrete in the first place. This may mean fixing leaks, grading around the foundation, sealing, etc.

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Moogy_C OP t1_je61p14 wrote

Great answer, thank you very much.

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georgenhofer t1_je5wpbg wrote

There is moisture underneath where that spot is showing.

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Moogy_C OP t1_je5x52t wrote

So you're saying ventilation would not help if that's the case? We haven't had a problem here in almost 10 years living here.

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georgenhofer t1_je5xl5c wrote

Ventilation would help, but there likely has been a lot of rain recently then, and runoff is going under your concrete pad. Likely the reason for the crack too, when freezing underneath.

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FellowConspirator t1_je6upfq wrote

That’s not mold, but rather efflorescence. Water dissolves minerals, the water with dissolved minerals reaches the surface where the water evaporates and the minerals form crystals.

There’s water soaking into the concrete from somewhere (surrounding soil, likely).

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lurkandpounce t1_je70qhw wrote

Definitely efflorescence. I've had this happen from water seeping up from below the concrete in a basement, and I currently have this in a garage where the water comes in on the car and when it gets to the concrete leaches out some of the minerals (not sure, some form of calcium or calcite?) and crystalizes as the water evaporates.

The only case that needs remediation is when the moisture is coming through the concrete (so, not the garage example above) and has enough actual water moving to pool on the surface. Other than that just sweep or vacuum away. Don't breathe the dust if it gets airborne.

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noeljb t1_je779cp wrote

Get something with Disodium Octaborate Tetrahydrate as an active ingredient. If it is mold or mildew this will take care of it. Mix it according to label for a 15% solution. Spray on spot just to moisten. Let dry, repeat once. Walk away, enjoy life.

It is a form of Borax, very stable and has a very low toxicity.

Oral LD50 is 2500 in Rats. .. .. .. Aspirin is 200.

I could not get pic to load.

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Few_Ad_5677 t1_je7ux4g wrote

Bleach breaks down into table salt, you’re bringing the problem back over and over again lol

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Moogy_C OP t1_je7zupb wrote

Makes sense, lol

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Few_Ad_5677 t1_je83e19 wrote

It’s actually pretty funny. You could keep doing it and it will keep growing larger and larger. Report back when it gains sentience

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