After I pulled out all of the old carpet and pad, I noticed that the concrete looks pretty shiny. Is this normal for concrete that has not been sealed in any way or does that tell me that it has ben sealed? I read another post on here that said just put a few drops of water on the concrete and if it was absorbed then it wasn't sealed. Is it normally absorbed right away, or does it take a little while?


Thanks,
kc

If it is sealed it will not absorb. If there is no treatment or adhesive contamination the water will absorb into the concrete quickly, but perhaps not completely, depending upon how much water you drop onto the surface.

It my be steel troweled so much it doesn't have a porous surface.

If your gluing, you may need to abrade the surface, to give it some tooth.

Could I use vinagar to clean and prep the concrete? Vinagar is a light-duty acid, so would that be strong enough to etch it?

Though I have never heard of using that method. I am highly sceptical that it would work. My experience has led me to grinding the surface. I have read that others will use 16 or 20 grit on a buffer type sander or scarifying bits to create a bondable surface.