Hello, I have really enjoyed all the posts about alternative energy and especially the rocket stove mass heater articles and forums. I am planning to build one in the next couple of weeks. Does anyone have any experience or advice about building out of concrete? I don't have a lot of access to clay soil and have been thinking I could build the bench/heat mass out of concrete instead of cob.I have access to large quantities of cement fairly cheaply. Anyone have any experience with this, or have any reasons why this wouldn't work. Any ideas about the heat storage capacity of cement vs cob? I appreciate any advice.
Marcus Grace : Someone has to do this, it might as well be you. You will still have to do a layup out doors first, so you will need some clay to make clay slip to temporarily
seal off the leaks that setting your rocket burner up dry will automatically cause to happen, You can make up the Feed Tube, Burn Tunnel and Heat Riser with fire bricks and
because your build will be permanent for good or ill you must, plan the insulation for the combustion zone, and the right amount of off-sets to protect your exposures !
A single bag of 'Fire clay' and Perlite and a yard of Builders Sand should get you through the parts that you can't don't want to substitute Concrete for Cob!
Concrete is more dense than cob, heat energy will flow through it slightly faster and you can use up lots of natural stone in making up sections of your Thermal Mass Bench,
This is where I ask have you been to rocketstoves.com for your PDF Copies $15.oo of Ianto Evans Great Book " Rocket Mass Heaters " there is STILL no other book
in any language with more Rocket stove /Mass Heater family information ! (And I don't make a dime !!)
Come back here often, with over 19,000 fellow members there will always be someone here that wants to talk about what you want to talk about ! For the Good of the Crafts!
Think like fire, flow like a gas, Don't be the marshmallow ! As always, your comments / questions are solicited and Welcome ! PYRO - Logically BIG AL
Success has a Thousand Fathers , Failure is an Orphan
Exit temperature from the barrel on a 6" system we have found to be around 400F. This is right on the cusp of what you can get away with for cement. I would recomend you consider doing a bell for your thermal mass though, less thermal shock on the cement. Check out matt walker's half barrel approach. If you are going 8" it might be too high. But it depends on your design, what temperatures you will be getting.
Our barrel temperature test can be found here at this blog.