Experimenting with burn tunnel materials

I am new to the forum, but enjoying the knowledge and experiences shared, I love this stuff! I have a question about different materials after reading about cob ingredients. I have used Hardi-Plank fiber-reinforced concrete siding on my house, the kind they sell at Lowe's and Home Depot, etc... and was wondering if anybody has tried using this stuff as a burn tunnel or heat riser?

Yesterday in the rain my kids helped me make a brick rocket stove that worked ok, but the bricks were wet and cold and it was a bit windy out. We had good rocket action and bad smokey smoldering action as well. I used patio pavers as a rudimentary material just to further my education and get the kids involved. They thought it was cool, but getting rained on in the back yard could only be so much fun.

All in all, I'm trying to build our educations one brick at a time and the forum is an awesome source of information, thanks to everyone!

Dan Henn wrote:
I have used Hardi-Plank fiber-reinforced concrete siding on my house, the kind they sell at Lowe's and Home Depot, etc...

Standard concrete cannot withstand the high heat in a rocket.
You would need something based on refractory cement.

Good to hear, i did the same, bought $17 worth of random masonry and set it up in a couple places to play around with the burn and show off the concept. Not sure how it would hold up but I know the Firebrick are proven and not terribly expensive if you live in civilization. I think I payed less than $3 per brick and $34 for a 15 lb tub of premixed mortar to hold it together.

To do it over again I think I would do an all brick riser, rock wool insulation and a rolled stainless outer shell (maybe two halves screwed/bolted together...). I dont have a ready source of clay so finding, blending.sifting.combining the perlite/clay slip is kind of a chore that rock wool sounds like it would replace pretty easily.