I'm planning to build an RMH to heat a greenhouse I've built. My home is built with AAC (Autoclaved Aerated Concrete), a type of insulating concrete block widely used in Europe and Asia but virtually unknown in the US. It is made by adding aluminum filings to curing concrete; the aluminum reacts with the lime in the concrete to create hydrogen bubbles, which get trapped in the concrete, which produces a lightweight concrete block with excellent insulating qualities. It's like a man-made pumice stone; the blocks actually float in water. The block is easily worked with regular woodtools.
I have a bunch of it left over from building the house, and I'm thinking they may be excellent for use in the hot areas (burn tunnel and heat riser). Has anyone ever used this or similar materials? Does anyone have any thoughts on how they might work? They are similar to kiln firebrick, though much less crumbly, and they take plasters well.
At any rate, I will try it for the combustion area (unless someone gives me a good reason why it's a bad idea) and let you know how it works!
Bubbles can be dangerous when heated, if the air in the bubble has water it will become steam and steam is too large for the given area the water was housed in.so be absolutely sure they are bone dry, even cook them in the oven first to dry them further.