expanded argila as insulant?

[joselb]

expanded argila = small balls (aprox. 1-2 cm) made of clay expanded with air, used in gardening.
I tested them in my butano stove, for many minutes, direct over the flames. They didn't burn. Also, they accumulate almost no heat. And they seem to be a good isolant, as expected, as they are permeated with lots of air inside.

My idea: to use them as thermal isolant. For that, the idea is to roll them into cement (with no much water) and throw them, let's say, arround the riser, inside a tube, like I have seen in the rocket stove pictures and book.
So, each ball will become glued to the other by the thin cement layer. Betwen them, just air... inside them, most is air too.

Do you have any experience with that? Any suggestion?
Regards
Jose

[Donkey]

If the clay balls are not ruined by the water (I have no experience with these) then this may work just fine. The cement may not handle the heat very well and could eventually crumble.
Good experiment, good idea.. Try it on a non-permanent stove and let us know.

[joselb]

Apr 22, 2008 20:38:01 GMT -8 Donkey said:

Good experiment, good idea.. Try it on a non-permanent stove and let us know.

Hi John, do you have a suggestion for the cement mix?
Jose

[Peter]

Hi,
Last year a Dutch couple in Portugal built a simple cook stove, following rocket principles. They used expanded clay granules as insulation. Not binded by cement, however. see www.cato-projects.org/ArLivre/RocketStove1.htm

[Donkey]

That's a nicely clean implementation of an Aprovecho style cooking rocket.
Oohh!! I really like the stove at: www.cato-projects.org/ArLivre/RocketStove3.htm
THAT is just cool. Simple, versatile and multi-use.. Very good.

Back to this thread:
OK.. I get it.. Googled it. Expanded and fired clay. Used in agriculture.

joselb, Before you use cement with these, try mixing them with a little clay slip. Use just enough to wet them lightly. This mixture can then be poured into a mold, allowed to dry and perhaps used, as is.
If this works you can avoid using cement entirely, which is produced by a hugely damaging and wasteful industry.

[joselb]

Apr 23, 2008 15:44:31 GMT -8 Donkey said:

Back to this thread:
OK.. I get it.. Googled it. Expanded and fired clay. Used in agriculture.... try mixing them with a little clay slip.....

Thanks John, I'will try something like that. The problem to me is to find a clay that gives the necessar "glue". I have lot of earth here, but I'm not sure about where to get a good clay.

[Donkey]

Good, clay-rich soil can be found around wet areas. Most commonly directly below a spring, or seep.

There are several tests for stickiness, expansiveness, silt, etc... Ideally you want a clay that is free of silt and doesn't expand/contract much during the repeated heating/cooling of the material.
The easiest thing is to set up a test space and just try it... Repeatedly.