BiggerPockets

i suggest white vinegar and a brush.....then throw some sealer on it.

the vinegar should work by itself, but just incase, i'd seal it (so that when/if you put carpet on there isnt a chance of it seaping up)....the vinegar smell will go away after a few hours.

Muratic acid. Careful with it though.

Don't use it on anything but concrete or brick. It will eat mortar grout (and your skin - again, be careful)

We have a home that had 5 German Shepherds in it before we bought it. It smelled like dog really bad. We stripped out the carpeting & padding and vacuumed to removed any lose padding and dust. After letting the house air out for a week we washed the subfloors down with bleach. We then took a roller and painted a primer that was made to hide fire damage. It's designed to hold in smells.
It worked and I received a 6 year lease.

Thanks to all that replied! There are some great ideas. I didn't know about Muriatic acid, or think about sealing the cement.

The issue I found about Muriatic acid is that the fumes damage stainless steel and can seep into the cabinet wood, if you don't neutralize it after application.

Sealing is a good idea, but some sealers are high priced.

So, I think I'm going to try a lot of vinegar (soak it), which is also an acid, and follow-up with a paint sealer like Kilz.

My only concern is, if I decide to ceramic tile, will the mud/paste adhere to the floor or come loose from the sealer.