Its refractory, I put it in there to do something different.. basically its a dense aggregate material with specialized cements that you add water to and mix like concrete but it will stand up to extremely high temps. They use it in foundries, steel mills, power plants etc. Anything where you have a shell the needs to be protected from extremely harsh emvironments. I am even thinking about shooting a insulating gunnite material in the cooking area that would allow me to hold in the heat better.