Native stone oven

[Wiley]

Welcome,

I'm the fellow building the steel dome oven. I considered many materials for a heat sink for my oven. One that I think might fit your criteria regarding cost (as in free, they have to pay to have it taken away) is spent moulding sand from a steel foundry. Doesn't have to be steel, our local foundry casts in bronze and they periodically dump all their sand and buy new. I have been told it has to do with the binders that they add to the sand to get it to stick together. The binders burn out and the sand needs to be reconditioned and often it is cheaper to start over with new sand than recondition the old. In steel mills the sand is/was olivine which is very good with high heat. Also in the past they used molassas as a binder. That's useless info unless you find a site where they used to dump spent moulding sand. Olivine sand is green in color.

There is a company named "Pivot" located in Australia that makes and sells a pizza oven that is two steel shells with sand in between. Here's a link if you are curious:
Pivot Stove & Heating Company

For my oven I decided on using crushed basalt with Fondu (calcium aluminate cement) as a binder. Basalt is also known as "traprock" and is recommended in several books on WFO construction. It is also very inexpensive where I live. I paid just over 13 US dollars for a long ton at our local quarry. I selected it over moulding sand because I could get it in greater quanities and closer than the foundry. Fondu isn't inexpensive and honestly in my application I probably could have gotten away with using lime as a binder. But I bought it and will try it.

Lots of ways to build an oven, some more successful than others. Even if your sandstone doesn't work as the heatsink it would probably make a great looking exterior covering.

Best of luck and there's lots of experience on this forum, just ask.

Wiley

[dbhansen]

This Wikipedia page has thermal conductivity ratings for sandstone and a bunch of other materials. Sandstone is listed as about 2-3, the same as marble and grease.

[adman2u]

I would love to hear about your luck if you use sawdust. FYI the first cooker I built was a smoker from mud and bricks - mud from our swamp - It lasted six years. I used corregated tin as the cover of firebox and another bent like a toaster for the smoker side. UGLY CHEAP GOOD A hurricane dropped my carport on it. I just finished a real one - photos in gallery - love this concrete