I've searched and found quite a few threads on cleaning concrete, but nothing specific to my situation. I just pulled up the carpet and padding of one of my bedrooms, which I'm turning into a nursery for my son's coming arrival. I will be putting down 5/8" engineered bamboo flooring in a floating installation over 1/8" foam with 6 mil poly vapor barrier.

The carpet padding was the standard congolmerate foam. When they put it down, it looks like they put down some sort of adhesive, presumably to keep the padding in place. Some of the foam bits seem to have reacted with this adhesive over time, and even though I can scrape the foam bits off, they leave behind a sticky goo that simply smears across the concrete.

a) Should I even be concerned about this? I'm a construction engineer by degree, and I admit that sometimes I'm a bit of a perfectionist when it comes to surface prep, measurements, etc. My concern is whether or not these goo spots (think "leopard" for an idea of the concentration of spots) will react with the 6 mil poly.

b) If this is a valid concern, can anyone recommend a product with which to clean the slab? My wife thought about using some a citrus cleaner/degreaser which she used when she refinished our bathroom, but since I found this great resource, I thought I'd put it to the industry experts.

On another note, there are some hairline cracks in the concrete, probably from before we did the foundation work to stabilize the slab (gotta love that Houston clay gumbo soil). They appear to be at or near the surface as they start/end about 6-12" from the walls. Should these be sealed up first, too? I haven't done the moisture test with the 2x2 piece of poly taped down, but I'm fairly certain that there isn't any severe moisture issue here. Suffice it to say that if there is, it will be corrected before proceeding. If there is not, do I need to bother with sealing these cracks?

Any advice would be greatly appreciated.

Try mineral spirits, or even charcoal lighter fluid.

Thanks for the quick response, Floorguy. My primary concern with those products is the flammability since I'm probably going to have to use quite a bit of it. I'm also concerned about the fumes, since my wife is pregnant and has had a difficult pregnancy without any additional external factors. Would the citrus cleaner not work, or are you just not as familiar with them?

Also, any thoughts on the cracks?

It's a floater! It is not going to matter if there is a little residue. Big clumps, yes, but a little residue, no.

We just had the same situation yesterday. We used our buffer with a hardplate and 36-grit sandpaper to remove the glue residue.

If you do this start the buffer on the concrete where there is no glue. Then work the buffer onto the glue gradually so some of the dust and grit will mix with the glue and remove it.

We were prepping the slab for a glue down installation. As Floorguy said you should have no problems with a floating installation if a small amount of glue remains.

Thanks, FG -- that's exactly what I needed to know. I'll be the first to admit that I may be paranoid and overestimating the significance of some things, so I'd rather ask the question and sound like an idiot than sit here a few months from now thinking, "Dammit!" A lot of times I've found that things I learned in school are great in an ideal environment but often impractical in the real world, so thanks for keeping me in check.

BuddyJ, thanks for sharing your experience, too. Based on what FG said, I think I'm just going to get the big clumps up and call it a day. Tomorrow I'm going to check the slab for flatness, so my focus may shift towards that challenge soon anyway.