Concrete slabs
Free Concrete Slabs great for ground cover or patio
Here’s the thing, Sparky. You very cleverly didn’t state the sizes of these slabs or estimate the weight involved. I’m gonna need a brazillion friends to help move one, and maybe rent a flatbed. I think you ought to be paying me to haul them away. Can’t wait until Cap’n Mac gives us the possible numbers involved.
Welcome To Fabulous Sparkyville 
That’s easy–concrete is right at 150#/cf.*
For 6″ thick concrete, that’s a square 24″ wide.
For 4″ thick concrete, that’s a square 36″ wide.
For six-sided octagons of concrete, it’s thirteen trout per stubborn cat.
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*SI ±2400 kg/m³
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Virtually everyone prefers Trachelospermum asiaticum or Hedera helix (in some climates, Dichondra (Dichondra repens) is a much preferred ground cover.
Unless one has a sportsball field, in which case, a tarpaulin seems more mete.
As a patio, using material over which motorized vehicles have operated, ever, is generally considered use of POL-poluted materials and represents an unknown hazard to all and every used of that surface. It’s also nearly universally prohibited by every EPA, State or National.
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