I have a contractor that is pouring me a slab for my garage that I am having built. He started the pour and didn't have enough concrete in the truck to complete the pour. There is about a 10'x10' section that has been sitting for the past two hours curing. The truck left so I guess he went bact to the yard for some more concrete. My concern is that the slab will have a weak area where the old and new concrete meet. They haven't returned to complete the pour. Should I be concerned or should the slab be good. Any help would be appreciated. John

As long as steel mesh or rebar in the cold joint was being used, your floor will be safe. A floor that size should have control joints to minimize cracks and needs to be cut a day later.