We sub all of our concrete flatwork out. But I have a customer who had a bad experience with her previous concrete driveway (cracking, in particular). And so they are having us redo their entire driveway and front landscape. But this time the customer wants us to go the extra mile on everything. She requested we excavate not only the concrete, but whatever is under it for 10", install 10" of new gravel, compact the gravel, install lots of rebar, and then install the new concrete. So for the concrete itself, I have the option of using 3000 psi concrete, or 4000 psi. for only a little more. My question is this; will the 4000 psi resist cracking more than the 3000 psi will? There are no big trees around, no tree roots to cause lift. And the foundation underneath will be about as [overkill] perfect as you can get. So it's not going to crack from lack of sub-structure, that's for sure. The only thing I can see cracking it would be heavy delivery trucks, which is what caused the cracking the first time, according to the customer. So I was thinking if we use the higher psi concrete, this would help prevent that from happening. But I am not really an expert on concrete. For those who are ... your thoughts?