The reason concrete is not warranted is because situations as this are really out of his control to some degree. The concrete comes from a supplier who is responsible for the proper ingredients and mix. Concrete analysis is out of price for the homeowner and is relegated to major companies.
If you opt for a new surface (the only other choice is a new driveway by another contractor) make certain that he applies a bonding agent prior to resurfacing. Do this quickly before oil and gas saturates into the concrete and makes proper bonding difficult.