I would like to know if tongue and groove sturdi floor can be used on a concrete slab. What sparked my concern was that I have read that when ramsetting your plywood there should be about 1/8th inch expansion gap between each sheet. If that is the case then tongue and groove is not an option.

I suppose it could be used if you rip off the tongue. There's no point in having it T&G and why pay more? All that's needed is 3/4" CDX plywood.