Concrete Not Drying?

[Kcourter74]

I've read this board religiously for about year as I considered epoxying my garage floor. I decided to take the plunge a few weeks ago and have spent the time prepping the floor (cleaning, power washing, degreasing, more degreasing, acid etching, more power washing, etc).

I was finally done with the prep last Sunday and was going to give my floor the whole week to dry. The forecast was for a beautiful weekend here in Ohio and sure enough as I type this it's low to mid 60s (same for tomorrow). My timing was working out perfect until the floor seems to not have dried completely. Throughout the week, it was cold (mid 40s) and very rainy. Only yesterday did it stop raining and today and tomorrow are beautiful (as I mentioned above).

Do I just need to wait longer? Or is something else going on here?

Thanks!

Here's the dirty floor before prep:

Here's when finished and notice the areas that are darker, seemingly not yet dry:

Another view:

Close up:

I had a dehumidifier running during the week and when i changed the placement, it even showed a footprint of the dehumidifier. Weird.

 

[Jack Olsen]

In the pictures, at least, that looks like rust. Did you use a steel brush to clean the concrete?

 

[Kcourter74]

Papa - thanks, I'll keep waiting. It does appear marginally better this morning.

Jack - I didn't use a wire brush to clean the concrete, just a stiff bristle broom.

 

[rburke65]

So it's the epoxy that is not drying, rather than the concrete, right?

 

[Kcourter74]

No, the concrete floor isn't drying after all the pre-epoxy preparation. My last hose down and power wash was 7 days ago and I still have what appears to be damp areas in the concrete.

 

[Edger]

Put a plastic bag down and something on top. Check it in the morning, is it very damp underneath? That is a quick way to see if moisture is rising. Washing the top will not put water into the slab.

 

[Jack Olsen]

Yeah. Do you know if there is a moisture barrier under your slab? You can duct-tape down a 24" square of plastic and see if moisture from the recent rains is coming up through the slab. If it is, you might not ever get good adhesion with epoxy.

 

[Kcourter74]

Not sure on the moisture barrier; I will ask my builder. I have taped down plastic a few weeks ago and it was perfectly dry after 24 hours. I only put it in one spot so I will do it again tonight and use various locations.

Thanks

 

[Zeke]

Sometimes a slab gets saturated. Not much you can do except circulate a lot of air and hope for drier warmer weather.

 

[Kcourter74]

Quick update, I pulled one of my moisture tests areas last night - no moisture. I decided to let the other two areas remain longer. I pulled one of them this morning and no moisture to speak of. I will check the remaining area when I get home tonight around 7pm.

What continues to confuse me is the one picture where my dehumidifier footprint is visible.

 

[Zeke]

Have you ever dragged a magnet in the sand when you were a kid? There can be ferrous material in the mix and it will take on a hue. Your dehumidifier kept its footprint dry.

I don't think properly washed sand does this not is it as likely if the surface is troweled smooth and sealed better. Older slabs can be a lot of things.

 

[Kcourter74]

So, Zeke, you think it's just moisture that needs more time to disappear?

Unfortunately, I'm at a point now where I don't think the temps will cooperate the remainder of the year. I'm not sure what kind of shelf life 100% solids epoxy has but I'm hoping I can hold off until spring/summer 2012.

Perhaps I'll get lucky and get a few days of Indian Summer where I can still get it down.

 

[Zeke]

Not saying how much moisture is still there. I'm saying the moisture from cleaning made the stains.
**** what due i kno?

 

[gabeancounter]

Here is my guess. Looks like silcone spray that was used on the tires soaked into the floor. The lines seem to be in direct relation to the tire areas. The dehumidifier looks like it needs a filter cleaning. lol.

 

[Kcourter74]

Well, the last of the 3 moisture tests was checked just moments ago and nary a drop of moisture or imprint of dampness on the concrete. I don't know if that's fullproof but it means at total of 4 different moisture checks at two different times all turned up negative. I have not heard back from my builder about the moisture barrier under the concrete.

It does appear to be a dried water stain of some sort. I think you are on the right track, Zeke. The question I have for everyone is do you think it's okay to epoxy?

 

[LegacyIndustrial]

If you suspect water, you may want to use a waterborne thin-mil coating. It can be applied to damp floors and will allow some water migration, through it, without any issues.

 

[Edger]

If there is no moisture in the slab coming up then you have a great slab to coat despite the visual appearance.

However, you may wish to do one last test with a strong detergent in case the stains are just surface oilyness which the acid will not touch because acid is not a detergent, not a cleaning agent, only a product that attacks the concrete surface, but not dirt or oil unless they come off with the concrete.

To do it simply, pour a spoonful of water across one of the stains, sprinkle on some laundry detergent powder and gently mix the two in a line across the stain. Leave for 10 mins, agitate again, leave another 10 mins then thoroughly wipe up the liquid, apply some rinse water, agitate and wipe clean, then repeat the rinse again so you are sure you have no detergent residue left.

If you wipe it clean it should dry completely in 15mins to 30 mins. Then look to see if it has made any difference to the stain. If it has you know what to do to the whole floor, but if you did not clean the floor I doubt that it would affect the bond of the epoxy anyway because the amount of oil residue, if it is that, would be very small and the solvents in the epoxy would tend to bond with it.

Oils usually carry dirt down into the concrete too which causes discoloration even if the surface oil has been removed.

 

[Kcourter74]

Edger - thanks for the detailed instructions. I did just as you suggested and the results were inconclusive. I'm going to do it again tonight and report back.

Scotty - can you point me in the right direction where I might find a water borne thin mil coating?

The other thing I haven't brought up (and I'm sure others noticed it in the pics) is I have some white splotches appearing to be efflorescence. These are all near the saw cut / control joints.

It's a riddle wrapped in mystery inside an enigma.

 

[Edger]

Edger - thanks for the detailed instructions. I did just as you suggested and the results were inconclusive. I'm going to do it again tonight and report back.

Scotty - can you point me in the right direction where I might find a water borne thin mil coating?

The other thing I haven't brought up (and I'm sure others noticed it in the pics) is I have some white splotches appearing to be efflorescence. These are all near the saw cut / control joints.

It's a riddle wrapped in mystery inside an enigma.

Hi Kcourter74, I did notice those white patches which definitely looked like efflorescence to me, but I was hoping they were residue from etching. Sometimes it occurs when you acid etch a slab, most of the time it is due to rising moisture. Your plastic tests were good so my guess is that they are caused by the etching process, maybe a reaction to something that was in the joints, I have had that happen to me before, but why do you have it at the front? That concerns me.

I am trying to rack my memory for a specific job without luck where I had almost the same unusual surface and I too had an unexplained mark on that job or another job where I sat some type of equipment just like your mark from your dehumidifier. I know it occurred at some time.

I recall all my failures because I had to know why, they were very few luckily and I am sure I coated floors that looked similar to yours without problems as long as I was convinced that the floor was porous.

It does worry me to see the efflorescence at the front because epoxy will stick to a concrete floor and bond 100% even if there is moisture rising as long as the surface is dry, but if the sun hits the surface it will heat the concrete under the coating and blow off pieces due to steam pressure and sun is likely at the front of your slab.

I just would have expected the plastic sheets to show some definite moisture. As you say, it is a bit of a mystery.

 

[Kcourter74]

Edger - I performed the detergent test again and I don't notice a visible change.

As far the efflorescence, I think I'm going to brush it off and just hope for the best. At this point, I have the epoxy on hand and I'm not going to ship it back. It will be a learning event for sure.

The only thing I can think of on the moisture tests is I somehow performed them incorrectly. I simply read what others had done which is take plastic and tape it down on all edges and wait at least 24 hours to check. Nothing. In fact, the only time I see moisture being held in is when the floor is drying and I happen to lift a bucket or gas can that was placed on the floor earlier in the day (when the floor was wet) That, to me, is natural though.

The floor seems porous. Water soaks in very quickly. It has a decent texture to it. It's not like 220 grit sandpaper but it not smooth either.

Thanks again for your feedback
Keith

 

[LegacyIndustrial]

Our Legacy's Standard epoxy kit is waterborne.
This product will adhere to concrete that is damp (not wet) and it will let a moderate amount of moisture pass through it.

Here is a link:
http://legacyindustrial.net/cart/standard-system-600-sq-ft-p-238.html

It's a great (2) coat system and frankly 100% solids has it's place but this is not it.

Good luck.

 

[Edger]

Edger -

The only thing I can think of on the moisture tests is I somehow performed them incorrectly. I simply read what others had done which is take plastic and tape it down on all edges and wait at least 24 hours to check. Nothing. In fact, the only time I see moisture being held in is when the floor is drying and I happen to lift a bucket or gas can that was placed on the floor earlier in the day (when the floor was wet) That, to me, is natural though.

Keith

I think your plastic tests were good enough and yes, anything placed on a damp floor will slow down the drying in that spot, as you say, that is natural. Good luck, I would be surprised if it failed, most failures are due to a surface that is not porous and yours seems fine. All the things you have said and done might be from a DIY, but your observations and actions have been very good.