allen lumley wrote:Remy Olson : at the bottom of this page find the ::--> permies >> forums >> energy >> Rocket stoves click on rocket stoves the next page is all
rocket stove Treads most resent 1st, scroll down, find, and click on Rocket mass heaters in Greenhousesyou want page 5 Paul Tofflemire, jan 26 2014 ,
The picture shows a Heat Riser Stack and the base of the Burn tunnel sitting on about 2'' of vermiculite setting on dirt, for a combustion core setting on concrete
twice the thickness and then a row of spaced bricks some backer board that will take years to fail and then the base of your combustion core.
Hope you find this handy, For the good of the Craft ! Big AL
Glenn Herbert wrote:Just 2" of perlite/clay under the combustion zone will not be enough to protect the concrete from heat damage in a long burn. You need more, either a bunch of material or an air space above the concrete. Putting a layer of spaced-out bricks with cement board on top to support the insulating layer a couple of inches above the concrete would be sure to work. There should also be some sort of reinforcing in the slab so it doesn't shift when it cracks (anything more than 4-6 feet long or so will eventually crack on exterior ground, sooner if it has a heavy load on it).
allen lumley wrote:Remy O. : This looks like pure 'vermiculite' packed tight, it like a good mix of Clay Slip (mixed to a thin pancake batter) and perlite is mixed with the perlite
just dampened to hold down silica dust, until snow ball sized balls can be formed, these balls when squeezed between a finger and thumb will 'pop' apart, this
is the mix that gets tamped down into the boxed under layer that the RMHs Burner Base gets built on ! When well packed they will support the bricks and
backer board, E & E recommend covering that surface with a heavy duty grade of Aluminum foil shinny side up to further help refract the heat back into the
Combustion core !
For the Good of the Crafts Big AL
Glenn Herbert wrote:I looked up this topic and found varying opinions, but the best actual information was that horticultural grade has varying particle sizes, which one commenter called good because it allows for tighter packing of particles and a stronger mix. I have also read somewhere (don't recall the place) that one variety, possibly construction grade, is treated to be water resistant and thus will not bind with clay as well.
I think you will be fine and certainly don't need to replace what you have, even if it's not the best possible variety after all. Do you have any left out in the open? Test it with the same mix you used, and dry it thoroughly. How strong is it?