I saw a number of posts I could have replied to but I thought it best to start a new post.
This relates to another earthen stove material.
Cob/adobe is not water stable. Portland cement does not breath and does not do well in high temperatures. Refractory cement is expensive and does not breath (I think). bricks are expensive.
There is another route which is not well understood by most DIY folk, but which has much potential. It draws from the ancient cements, the pozzolan cement of Rome and accelerated sodium silicate cements used by the Egyptians and also in modern times. The generalized chemistry that includes these is called geopolymerization.
The result is like ceramic, it breaths like terra cotta and is water/acid stable. But it can be cured with a fire inside the oven. Despite the root "polymer" in the name, there is no organic plastic funny business. Just, alkali (sodium hydroxide) and alumino-silicates (minerals). The DIY route of making this from fire ashes, local clays and lime is not well explored or documented.
Expensive? There is no centralized production available to citizens. But I am in the process of being able to make small batches, and even I could ship enough binder to build a BIG oven inside the US for under $100 (including materials, labor, shipping etc). Mix this with another $100 worth of cheap truckload type material to get your oven. If you have access to a ceramics kiln, then you could make it yourself for much less.
I am not offering anything for sale. I am just a student of the hard sciences pursuing an idea that sounds really excellent. And I am promoting my project to explore and publisize this technology, which will result in the compiled experiences of people from many backgrounds working on a variety of different applications.
Please follow up with me if you want to be informed of developments in this project, or if you want to participate/contribute. I cannot promise to post back here as the project unfolds.
Proposed Geopolymer Project
I am trying to raise money here: Making Geopolymer technology accessible — Kickstarter
Re: Geopolymer ovens
Thanks Elliot good luck with your project and studies, us "Aussies" love anything thats cheap to make so i look forward to your findings.
If it means pizza and beer we will build it.
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