Concrete resurfacing issue: Prep for epoxy coating


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Old 05-07-08, 08:49 AM
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Question Concrete resurfacing issue: Prep for epoxy coating

I am in the process of preparing my garage floor for an epoxy coating. The long and short of it is that I'm getting some staining that's coming through certain areas of a thin resurfacing concrete layer that I've applied. Read on for details. Your thoughts/suggestions are appreciated.

The concrete pad is about 40 years old and spalled (1/4" deep or so) in certain areas, but overall the pad is in good shape. The spalling (if I'm using the correct term) appears to be located in the areas the would coincide with a car's tires and areas under the center of both axles. I used a 3000psi pressure washer (PW) spraying a mix of water/Zep Chemical's concentrated concrete cleaner (a coupla times, I might add). When complete I rinsed with the PW and clean water, and could immediately tell the the areas that still beaded up water. On these areas I applied a 100% solution of this cleaner (Zep recommends, 50/50 for stubborn areas....), and used a scrub brush to work it in, and allowed it to sit on it for 10 minutes or so. Another PW rinse would follow any of these spot applications and I would use a squeegee and allow it to sufficiently dry. Once the floor was clean I put down Quikrete's Concrete Resurfacer mix over about 30% of the floor in areas cracked or spalled. Once this should have been dry (the next morning) I noticed what looked like small areas that were still wet (darker color, not unlike freshly applied concrete). Despite this initial thought, these areas haven't changed much in color at all and still look 'wet'. I used a plastic sheet taped to the floor directly over one of these stains and after waiting overnight the underside of the plastic is dry dry dry. Is this fresh concrete overlay sucking up deep oil in the concrete?

Do you think it's oil? I haven't checked to see if it beads water (probably the best test). Should I just degrease this new layer? It's been a few days since I last put down the new thin concrete layer, so if it actually is oil, I'm sure it's been pulled up as much as it will.

Thoughts?

Attached are the pics of what's going on.
PIC 1
Pic 2
Pic 3

Thanks for your help!
SkydiverMN
 
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Old 05-07-08, 10:13 PM
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wouldn't hurt to degrease it, shure looks like oil spots.
spalling is the correct term as far as I know. probably caused by road salt coming in on tires and undercarriage.
life begins when the kids leave home and the dog dies
 
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Old 05-08-08, 08:18 AM
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Thumbs up Ain't oil...

It doesn't seem to be oil. I put water on the stains and it simply wets the concrete. No beading, bubblin', etc. that's characteristic of water on oil. Also, there's no condensation on the underside of a plastic sheet. Today, the stains are slightly less visible too. Seems water-like, but dunno.

Basically, I just dunno.

I'm going to go to the etch process and then just paint the epoxy gunk on it, per instructions. Maybe even a bit on the thick side, but I'll let ya know how it turns out. I'm sure that everything will be just fine. Moving on.

Thanks!
 
 

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