Looking for Concrete Experts!

[Winmon]

I am having some issues with blistering on my newly epoxy'd floor. Rustoleum had me sent them some samples of the blisters to anaylze them to find out what is causing it. They sent me a detailed report saying it is due to "major water vapor transmission". I am now in the process of trying to find out WHY I am having water/moisture coming up. I have a vapor barrier under the slab and I performed 2 moisture tests by taping a 2'x2' sheet of plastic down for 24 hrs to see if I get any water/moisture trapped under the plastic. No water was present on either of those tests. I am wondering if the moisture is due to the fact I sealed the slab with a sealer right after the pour was done. I then (6 months later) stripped the sealer off to get the epoxy to stick. BTW, I performed the 1st moisture test prior to removing the sealer and the 2nd after I removed it. So, I am thinking that maybe the water that was trapped by the sealer is just now trying to escape (just now curing?) now that the sealer is off and once the moisture all escapes it will stop. Another thought of mine is it is water that got into the pores of the concrete when I rinsed the floor with a pressure washer (I rinsed it twice, once for the initial clean and the second when I rinsed the muratic acid). Maybe the pressured spray caused the water to get deep into the pores?


Does anyone have any thoughts on my theories and if it possible that is what is causing my problem? Can anyone think of any other reason I can be having moisture issues even though I have a vapor barrier under the slab?

 

[bmwpower]

How long did you wait before you coated the floor (after washing it)?

What type of barrier did you use? It's possible that it has failed (holes in barrier) and/or not sufficiently impermeable to the water you have under the slab. It only takes a little water to travel up the pores via capillary action and get to the surface.

 

[Winmon]

How long did you wait before you coated the floor (after washing it)?

I only waited a day to dry. The temp was about 65*.
I am starting to think that is part of the problem.

Here are some pics of what the blisters look like. The 1st pic is by far the largest blister. The rest are the size in the 2nd and 3rd pics, which are about 1/8" inch in size.

This afternoon I sanded down the area that is in the 1st pic. That largest blister was right over a area that had some grease on it that was shot out from the Edco surfacer during the grinding process and I remember REALLY focusing the pressure washer on it during the cleaning and etching. Also, I circled it with a Sharpie a couple weeks ago to see if was expanding in size and it had not. The blister also seemed to be hardening up. I even broke a razor blade on it when I removed it prior to sanding the area. It also seems like alot of the blisters that I am now finding are alot smaller then the first ones I noticed were.
The other thing about the pressure washer I did not mention was I had the nozzle set on a strong spray (narrow) as opposed to having it set on the "fanned out" spray. I also had rinsed it several times and at times had alot of standing water on it which I squeeged off. I then gave it only a day to dry (the temp was about 65*) before I put the epoxy down.
I am going sand down and remove the blistered areas and then do a moisture test with the plastic. We will see what happens. I did buy an extra kit in case I had to repair any areas. It sure does seem like the problem is pointing to the cleaning process/pressure washer and lack of enough dry time. I will post what the results are.....

What type of barrier did you use?

I was not smart like you were (by buying the vapor barrier yourself to be sure it was a nice one) and I trusted the concrete guy to do it so I have no idea. I do know that one did go down. I was very adamate though about letting the contractor know that I wanted NO moisture coming up through the concrete

 

[PAToyota]

I'd say that washing it the day before is definitely the problem. You're talking about allowing four inches of concrete (or more) to dry out... The surface may look dry - but I'll guarantee that you still had a lot of moisture in the slab.

 

[bmwpower]

I'd say that washing it the day before is definitely the problem. You're talking about allowing four inches of concrete (or more) to dry out... The surface may look dry - but I'll guarantee that you still had a lot of moisture in the slab.

I might have to agree here. I let mine sit for 2 weeks before coating, but I was in 40 degree weather outside and my floor is 8" thick.

 

[Tyson]

I hope I don't have any problems....I waited about 36 hours for mine.

 

[Winmon]

I'd say that washing it the day before is definitely the problem

Actually it was a little more then a day. The week it was done, I washed it on Tuesday, did the muratic acid on Wednesday, gave it all of Thursday to dry, then put down the epoxy on Friday with the second coat going on Saturday.

The surface may look dry - but I'll guarantee that you still had a lot of moisture in the slab.

I am thinking your are right.......I had not realized concrete was as porous as it is. I am going to sand down all the problem areas, give them all time to dry out, do a moisture test on the affected areas, then HOPEFULLY patch the areas with the epoxy. Boy do I hope it fixes it!!!

 

[Luckydevil]

Did you acid etch? I've found that does wonders on grease/oil spots before you lay the epoxy down.

 

[04 Navi]

So then I must ask, is the Griots Garage stuff water based then? The reason is that when I installed their product as per the instructions, they were specific that the cement not be completely dry. After rinsing off the muratic all they said was no puddles, but cement should be damp. It has been several years since I did it, so memory may fail. BTW the Griots stuff worked very well. Five years on it and the only small chips I had were where I hadn't completely gotten the old paint up. Otherwise it was great.

 

[JohnZ]

I didn't let water/moisture of any kind anywhere near mine before it was coated; it cured for about 4-5 months during home construction (with a triple moisture barrier under the slab), then was steel shot-blasted, and the first coat was poured that same day, second coat the following day.