Max,

Here's a link to the shelving I have: Lowe's. It's actually called "Maxi-Rack". Back in the old days it was Gorilla Rack. I'm kind of partial to industrial looking stuff and these are great.

I have one shelf that likely has 750+ lbs. aggregate on it, doesn't sag, whine or moan...

Bob G, potentially what you could do, if you are OK with the idea of setting your machine tools in one place and not moving them around is to have "pylons" built in to the slab at the areas where the machine feet lie. It will promote cracking a little earlier, but it is after all concrete, it will crack eventually...

Mike