I am bored and decided to rebuild our firepit. I want it to have a concrete foundation. It will have a concrete ring that had a 48” inside diameter and 53” outside diameter and 6” deep. I estimate 10-11bags of concrete. I will also add 1 piece of 3/8 rebar (16’). Can I just keep adding bags (by hand-mixing in a wheelbarrow) Or will that be too slow and screw up the pour time/drying time? Should I rent a mixer? Why type of concrete should I get for a fire pit? I am using field stone from our property for the walls.