Mine was at least 5" of 304 crushed limestone, vapor barrier, rebar around the perimeter and mesh in the middle. 5" concrete. Make sure you get at least 3000 psi concrete. A lot of times contractor substitute 2000 psi to save cost. If it's a garage floor and you want to power trowel it for the smooth finish then don't use the fiber.
My wife, a Civil Engineer, said to use rebar with "chairs". She says that you can't "rake" the rebar into place. She also suggested using fiber as well. That's just her two cents worth.
I would absolutely cut the concrete. If you use rebar, make sure it isn't set up too high. I don't know if you can attach pex to standing rebar or not, maybe a plumber will know. My pex was attached to wire mesh that was laid down on the insulation, conceding that the mesh was only there to hold the pex. I poured a 28'x56' slab for a pole barn that I had built this summer. With the research I had done for my shop fresh in my mind, I used 4" of fiber-reinforced 4000 lb concrete, with a couple of deeper pods for a future lift. We did use machine-compacted stone and a vapor barrier, but didn't do radiant floor heat or epoxy. Before we did the epoxy at the shop, there was no evidence of the fibers from the concrete, and same for the pole barn. Both were highly-polished. Despite my best efforts at the shop, we did manage to hit the pex while drilling for one of the thunderbolts for the lifts :rant: . I miscalculated the width of the new lifts and tried to straddle 1 pex line. I took about 90 pictures of the whole project (lots of pictures, esp of the pex, is HIGHLY recommended!) and when we opened it back up to fix the pex, we could see that the concrete had pushed the pex just enough so the picture we had for the location of 1 pex line was slightly off. It really was no big deal to fix it. I think I spent more time worrying about it than it took to fix, but it would have been much nicer if things went as planned! Good luck!
One of my frends has worked with concrete for over 30 yrs. I've seen his work for years so I trust him. With his help I had my garage poured 2 weeks ago in sub Zero weather but there is heat from another garage attached to it. Busted out the cement with a sledge and prybar with freinds. Added zero 3/4, tamped it and poured 4-5" with 1% calcium. No fibre mesh. We used the wire mesh and as it was raked it was pulled up. It was finished with a machine and coated the same day/night The size is 19'x28' cut once down the center two times the other way. Within two days where it was cut cracked to the walls like it was supposed to. Still haven't drove on it as I had to fix the spaghetti wiring and dywall. Just painting tonight, all night. Ray
I did order the oxygen barrier pex. Ended up with 5-6 inches clean stone base. I will do the vapor barrier next then try to figure out the rebar. Thanks to eveyone for the advice!
