I need to create a fire pit / fire bowl that sits on top of a gas connection. It's basically just a concrete tube that's 42" across and 16" tall with 2" - 3" walls. The top and bottom are both open and a fire ring pan will sit in the top opening.
I had thought that maybe I could find a piece of foam that's 48"x48"x24" and just cut out a circle that's 40" and then cut it again at 42" while securing the 36" - 38" circle back in the middle to make a mold.
The problem is that I can't find a piece of foam like that that's not hundreds of dollars on the internet. Does anyone else have a cost-effective way for me to build / form this mold so I can pour my concrete fire bowl? Build a larger foam pieces out of smaller ones? Spray foam? Something else?