I don't know about potting mix but I think you can seal the concrete so that it doesn't stain. Kind of like the treatment that they use for concrete counter top. I don't know how expensive that is going to be. Alternatively, you can try laying tarp down (I think you can buy the clear ones by the yard in a fabric store) where you are going to set your containers so that the moisture doesn't get onto the concrete.

Recently noticed a friend using clear vinyl draintrays meant for kitchen counters on her deck under large pots. Three sides had a raised lip of about 1-inch, the fourth side curved down to drain water into sink and this side she had extending over the side of deck just a bit. Said it really worked well. Hope this explanation makes sense.

Might not solve your problem, and maybe not practical if you have lots of pots, but thought someone might find it useful. josh

Have a new colored concrete patio and Miracle Grow Garden soil in my potted plants have left dark black stains over a third of it. Looks horrid. Anyone know how to get stain out? Tried patio concrete cleaner and heavy duty power washer and it didnt do anything!

Miracle Grow potting mix stained my not even a week old concrete. 😡

Judith, the power washer didn take the stain out of mine either.

If your handy you can do this yourself, but I recommend getting a professional to clean it. If it was previously sealed, the sealant can be stripped and cement cleaned using muriatic acid.