Not much here but Kelly asked about it so I thought I'd post, maybe something someone can glean. My first attempt at a castable furnace I decided to cast four wall section with tongue and groove joints. Four segments to allow for expansion and tongue and groove to limit hot gas escape. Used a piece of 12" pipe (12-3/4" O.D.) and formed for a quarter of the wall. Then poured the first segment. Pretty stiff mixed per instructions. These expired bags of 3,500F abrasion resistant refractory had been given to me as expired materials. But it sure flows. I could not pile it up like mortar and had a thin pour. So after a little head scratching used scrap lumber to step it up. And the second one was much better.