Gary. wrote:
I do not know how they grade concrete, but I do know they have concrete that is mixed for different loads. I had a driveway poured and it was only 3500 and ended up with a crack. Someone told me it should have been 4000 grade concrete. So also check the grade of concrete that will be poured. Good Luck.
I'm no concrete expert either, but I've seen runways with 18" thick concrete crack too. Not to mention the freeway concrete. Yes, I realize it's a completely different use, but I think concrete is subject to cracking no matter what.