So awhile back I dumped my Vision grill over backwards and broke the firebox. About 3 weeks ago I did a repair using Refractory Cement. Sanded down the 4 broken areas and the firebox and glued them back together. They suggested waiting at least 24 hours for it to dry before curing it and I waited 48 hours. Did a small burn at about 90 degrees for about 3 hours (easy to do when it's 95 out) and then stepped it up to 150- 2 hours, 250 2-hours, 350-until it burned out overnight. The next day it had small bubbles within the cement which is moisture working it's way to the surface which why you should let it dry 24 plus hours. But maybe summer in Florida on 90 +heat and 85+ humidity it did not dry out. We have done several cooks some at high heat and it seems to be strong, no cracks or movement. It could always be redone if it did break. The free replacement came from Vision yesterday, guess I will install that and keep the other as backup?? Or keep the new as backup?
So I do think they are repairable.