That's not a good enough reason in our opinion, 2) When we insisted on a 4,000 psi concrete mix, they went along stating that it would cost a little more. All they have to do is request it and it costs only a $100 to $300 more, 3) Most contractors said a 4-inch thick driveway was needed.he existing driveway was about 50 years old and had some huge cracks in it. Last summer we installed a new 24-foot wide x 44-foot long driveway in the Washington DC area. We hired a concrete contractor to do the job.