The wall section alone would require a form and almost half a cubic yard of concrete. The weight of the wet concrete would be considerable - whether enough to collapse the floor or cause it to sag (this is where the weight would bear - not the wall), is hard to say, but the weight would most likely be in excess of the floor design load for residential construction. Unless reinforced with wire, the concrete would also be very prone to cracking at a thickness of only 2".
Slate, brick, bluestone, cultured or natural fieldstone would all be better choices for both the floor and wall. Be sure, however, to check your local building/fire code. Any option may require an inflammable barrier under/behind what you install.

Thanks for the info. As usual, hubby beat me before my questions were answered. He bought Lone Star stone (a cement that looks like field stone but only 1/2" thick) and all the stuff necessary to do the walls. We are now going to do a cement floor because the 2x4s don't even hold a side-by-side frige without sagging let alone a cast iron coal stove (when are they going to realize the wood joists nowadays are junk?), rip out pine wainscoting and drywall, and do the stone halfway up with reinforced wire, while at the same time make provisions for the heat to go through the floors, etc. That is the main problem living here. . . very cold floors. We are going to do slate for the hearth area.

I thank you for your answer. I would welcome any further suggestions. This stove is even thicker cast iron than we imagined and should last us forever. Hubby is very, very happy with it so far (haven't used it yet as we just picked it up today) but feels it will be the best stove we have ever had. The thickness is even greater than a Fisher wood stove and thicker than his Kenmore "kitchen" stove in the garage....and both run us out of the area because of the heat. LOL

I've no idea if they're available in your area, but old (or new) slate roofing shingles are excellent for hearths. They are thinner and lighter (easier to cut, too) than slate designed for flooring and can be secured with thin set type mortar to a base of something like fiber cement board.
You're right about the quality of lumber today - I'd say over half of what's available today would have wound up on the reject pile 20 years ago.