Concrete expert needed.

[GPIDEAL]

It's true, if the slab area is large enough the concrete will crack. If you cast a slab 1m by 1m odds are it will not develop cracks. Now cast a slab 8 m by 12m without any sawcuts and I guarantee it will crack regardless if the slab is heavily reinforced or not. I have seen it happen about 100 times in the last 4 to 6 years alone, no lies. As I noted before, concrete contains water, one expects it to crack. The skill of the design engineer is to force the slab to crack within the deep sawcuts. By keeping the sawcuts relatively close and by weakening the slabs at the location of the sawcuts the chances are very high that the cracks will develop within the sawn joint. Another thing to keep in mind is that square slabs and square sawcut pattern that runs perpendicular to each other should be maintained as much as possible.

I'm not saying you're wrong in a general sense but each situation is different.

I've seen pads at least 12" think (not a huge area) with heavy rebar not crack. I know of floor specs and actual construction with steel fibre reinforcing that are designed to be crack free. Some came out 100% crack free.

 

[GPIDEAL]

This is great! Thanks again!

Yes it's excellent (especially the point about keeping the drainage holes on the bottom) and so is the OBC abstract and the comment about insulating foundation walls.

Another point is you should at least allow 30 days of 'air-drying' for an exterior slab, especially if cured with a membrane sealer BEFORE freezing temperatures occur, to prevent spalling.

 

[Cassini]

I've seen pads at least 12" think (not a huge area) with heavy rebar not crack. I know of floor specs and actual construction with steel fibre reinforcing that are designed to be crack free. Some came out 100% crack free.

There is a design rule to reduce cracking where the interval between stress reliefs must be less than 30 times the thickness of the pad. As such, a 12" pad with heavy rebar and a small area will have a much lower chance of cracking.

Additionally, anyone pouring a 12" thick reinforced pad, is probably doing their design homework too. For instance, making sure the pad is properly supported, and kept at an even temperature year round (preventing frost), can make a huge difference in crack formation. Thick pads are routinely used as vibration suppression mechanisms in heavy industry, and I am not aware of any instances of them cracking. However, those same pads are also designed to do the job they were intended to do, crack free.