Double Reinforced Slab on Grade Contraction Joint Depth?

[SteelPE]

I have a project where we are installing an exterior reinforced concrete slab. The slab is to be 10” thick and will have two reinforcing mats top and bottom (#6@12 bottom #5@12 top). This particular slab will have a radiant heating system installed on top of the top reinforcing mat.

I have questions regarding the top mat/radiant tubes and the sawcut joints that we typically put in slabs on grade. Our typical detail requires the GC to cut the slab a minimum of ¼ of the thickness (in this instance 2.5”). However, this will force our top mat to be placed towards the center of the slab (to avoid cutting the bars and the radiant tubes placed in the slab). We would like to push this mat has high as possible in the slab (to reduce the amount of cracking that may occur under loading), but we have concerns with placing the mat to high and having the radiant heating tube be cut during the installation process.

One option is to reduce the depth of the saw cuts to maybe to 2” or even 1 ½”. This will allow us to raise the bar fractionally. The though being that the slab is reinforces so shrinkage shouldn’t be an overly large concern.

Am I overthinking this?

 

[Enable]

No matter what your control joints won't weaken the slab enough to dictate where the cracks occur. In highly reinforced slabs you have random cracking due to irregular conditions in local restraint and that's just what we have to live with.

Specify a shallower control joint. The contractor won't dare cut anywhere near the specified depth anyways. Matts move during placement. Cables/tubes float. Even if you move the top reinforcing matt closer to center I doubt the contractor would change their approach.

Your best bet to control cracking in these situations is decent concrete (read: w/c = 0. 4 to 0.45) and a full 7-day saturated wet cure.

 

[Settingsun]

Would you be better off deleting the saw cuts to remove the risk to the hearing tubes? Either jointless slab or formed joints.