I have build the first dome with 5:1 ratio of vermiculite Portland cement and the dome was quite crumbly. I have decided to redo it and use the normal cement with the same ratio. I have then cover it with a light render of cement, sharp sands vermiculite. I am waiting a couple of weeks before removing the gym ball.
Do you know if normal cement is good enough?
Good enough for concrete not so much for pizza oven
I am in the process of building my own pizza oven as well, actually just finished the slab for it and ready to start the dome. one thing that i have read MULTIPLE times is to actually use perlite NOT vermiculite. One perlite is made from lava ( much better for heat ) second the ratios I have come across are 2:1 as 5:1 sounds like it wouild be way too crumbly