My concrete contractor is constructing an 800 sq. ft. patio here in Utah. After removing the sod, and packing down the "fill" dirt from the original home construction (6 years old) with the skid steer, he said that they can pour directly on this surface. The picture is 2 days after the rain showing where the water is still evaporating at the edge of the grade and the rebar that they put down. It has rained once (the grade seems ok) and the dirt is now very hard, but it varies in texture from organic to primarily gravel near the house and under the previous steps and stair landing. You can also tell the difference in soil composition by how quickly the water has evaporated. I am in a hurry because they will be pouring this week and I want to know if this is an acceptable practice and what are the problems with it and what would be the benefits of laying down a consistent gravel base. This is just a patio, so I will never be parking on it or putting anything heavy on it. We do get several freeze/thaws a year. Should I request that the gravel be included in the cost as it was something that should have been done from the beginning? Thanks in advance!!