|
Post by marcos on Oct 5, 2020 20:30:29 GMT -8
I'm gonna put down an insulative layer of perlite for the cob base of my RMH tomorrow, and am trying to decide whether to use clay or cement to bind the perlite. A mason heater builder recommended perlite-cement at 6:1 as it has more compressive strength. I generally use clay over cement whenever possible, but this is a build in my home and I don't want it to fail. Any suggestions?
Thanks!
|
|
|
Post by Dan (Upstate NY, USA) on Oct 6, 2020 0:44:38 GMT -8
I used high temp cement under my J-tube area with perlite. Then laid my firebrick over that.
|
|
|
Post by martyn on Oct 6, 2020 2:52:44 GMT -8
You are not giving away much information like how big or how much weight you want to support? You can successfully mix vermiculite or perlite with standard Portland cement but the area needs to be captive ie a brick surrounding filled with the mix. I build pizza ovens for a living and we used to use a 5-1 insulating vermiculite mix under the oven base (perlite is fine just more difficult to mix) but for the last 6-7 years ceramic board has taken its place. Basically ceramic board is at least twice as efficient so 3’’ of board is just about right for a oven base but you need 6’’ of Vcreat to match it, but then you have the issue of drying out the perlite or vermiculite as it is very water absorbent and can take weeks of drying before it really starts to work as an insulated slab.
|
|
|
Post by gadget on Oct 10, 2020 20:48:22 GMT -8
I have had good luck with clay. Cement dehydrates at temps seen in cooler parts of heaters.
Perlite layer is not a fire wall. What substrate is the heater going to be sitting on?
|
|
|
Post by wrekinwanderer on Oct 11, 2020 13:41:08 GMT -8
Just jumping in, with relation to making an insulated back wall for a bench.
For a poured insulative clay/concrete wall would you recommend adding gravel as another aggregate to give extra strength and bulk to a freestanding structure?
Ohh, I've got some broken bits of old insulated firebrick I could chuck into the mix. That could work as a bulking agent, although not the strongest stuff in the world...
|
|
|
Post by wrekinwanderer on Oct 11, 2020 14:04:13 GMT -8
Okay, just checked. No other aggregates needed...
|
|
|
Post by gadget on Oct 11, 2020 20:51:47 GMT -8
Just jumping in, with relation to making an insulated back wall for a bench. For a poured insulative clay/concrete wall would you recommend adding gravel as another aggregate to give extra strength and bulk to a freestanding structure? Ohh, I've got some broken bits of old insulated firebrick I could chuck into the mix. That could work as a bulking agent, although not the strongest stuff in the world... I would save those bits of firebrick for use in a higher temp area. Broken fire brick makes for good grog in DIY heaters, especially if your working with limited material options.
|
|