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Salt in my slab

U

usmc1978

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Aug 1, 2025
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Had a garage floor poured 24 yrs. ago. Didn't seal it, didn't know anything about that. Last year I noticed spalling, so I decided to seal. Used Euclid Chemical Super Diamond 350. Followed mfg instructions for cleaning the slab. In addition, I followed that with a pressure wash. Let it dry thoroughly, then applied 2 coats of the sealer. Looked great for a week or two, then I noticed white areas. Powdery. Turns out its salt. No idea how it got through the sealer. Now I want to put another coat or two on those areas, but I want to make sure the damned sure salt doesn't work its way up again. Suggestions on prepping before resealing?
 
PS, on the pressure wash, I didn't use any soap. Only water. Wanted to make sure I got rid of all of the TSP I scrubbed with, which was part of the mfg prep instructions.
 
The technical term is efflorescence, a common sight with older unsealed slabs and happens due to moisture. I'd start with a mild acid rinse, vinegar solution or some of that commercial stuff and make sure you're thorough in cleaning. Let it dry fully and then place a big plastic sheet and watch out for moisture. If there's not moisture it means you did a good job, so you should seal it and apply another layer of topcoat.
 
Thanks, SetInCement. A couple questions: I applied 2 coats of sealer before this occurred, so after getting rid of this effloresence, I'll put down another coat? And what do you mean another layer of topcoat? Referring to another (4th) layer of sealer?

Let me add this: I talked to the mfg of the sealer. The guy (tech assistance) didn't even know their own prep instructions called for washing with TSP before sealing. He acted as if this condition isn't a problem. I asked how the salt is coming up through the sealer, and if it's coming up then I must assume that this year's salt and whatever else will penetrate the sealer to the slab. He said nothing should get through into the slab, which makes zero sense to me, since there's obviously a pathway OUT of the slab. He said the sealer breathes to let moisture which might be under the slab get out. This makes me wonder why they call it a sealer, when it's not really sealing much. Furthermore, I laid plastic over the entire garage floor before pouring.

Comments on this?
 

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