With any luck these pictures will work and won't be HUGE.
The green tubes were formerly a 12 row planter frame and are 7"x7"x.375". The round discs were opener discs for a John Deere air seeder. They are about 18" in diameter and are about 1/4" thick. The shaft inside the tube is about 1 1/4" and was the feeder house reverser drive shaft on a 9000 series combine. I cut holes in the tube with a torch and the shaft sticks through about 1/2" on either side of the tube. I ground a bevel on the bottom of the tube where it was welded to the disc with a wire feed welder (.045 ER70S-3, 75/25 Ar/Co2). The rebars welded to the sides of the tube were attached with 7018 rod and are 1/2" diameter.
I will make some plugs to keep the concrete out when I pour the floor and keep things from falling in after the floor is done. As usual I overbuilt these but the price was right--all it cost me was a little gas for the welder and a little oxygen and acetylene for the torch. BTW, the slab will be 6" thick.