In response to the Twitter video of pouring the floor, it is sad to see that even in 2016 concrete contractors are still using welded wire mesh in their pours. Welded wire mesh provides no structural strength to concrete, very little in the way of crack control and only serves to make eventual concrete removal more problematic.
Note how the concrete truck drives over it, forcing it down to the bottom. Then one worker haphazardly pulls it up only to have the finishers step on it and force it back down again. Reinforcing is best when it is placed withing the bottom third of the slab so as to spread out concentrated floor loads. Put it in the middle of the slab or higher and there is no benefit from it. Put it at the bottom or varying in distance from the bottom to 1/3 back to bottom also is of no benefit.
If you are going to have a concrete floor poured, insist on using fabricated rebar mats instead of welded wire. These mats are made from deformed rebar in sizes 3, 4 or 5 and are welded together on various spacings. Very easy to place, they support the weight of workers (but not the concrete truck) and allow for the concrete to achieve its maximum strength and weigh supporting ability. You can also manually lay rebar and tie it up, but that is fairly time consuming.
I support a 260 ton stationary steam engine on a 7" thick slab. I used No. 4 rebar 12" On centers throughout. I can show you where that slab actually flexes under the weight, but I have nothing larger than a few hairline cracks because it was engineered correctly in the first place and the rebar is exactly where it needs to be and is doing the job it was designed to do.
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