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Old 05-05-2014, 04:25 PM
david s's Avatar
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Default Re: Vermicrete or Perlcrete as last layer

Quote:
Originally Posted by cobblerdave View Post
G'day
I have wondered the same thing too. Because these ovens are homemade there will probably never be a truly exhaustive study like you get in construction for example.
These ovens stand up and keep working so no one to my knowledge has had any reason to pull a working one apart. That would be interesting.
I suspect that in the top layer the Portland does break down. The pearlite/vermiculite is packed together during its time as a liquid cement mix. The underlying pearlite continue to hold the upper in position and the upper continue to protect the lower from the heat. This of of course pure speculation. But you have to admit it continues to work.
Regards dave
Yes this is exactly what happens. The top layer (about a millimetre) of vermicrete/perlcrete may break down if it gets hot enough, but as the temperature drops away any deeper the stuff holds together ok. When testing insulation panels made of perlcrete, vermicrete and foamcrete, I discovered that where the panel was in direct contact with the heat source (over 400 C) the surface was dusty but the rest of the panel was quite ok.
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Old 05-05-2014, 10:13 PM
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Default Re: Vermicrete or Perlcrete as last layer

Thanks Dave
Your certainly our R & D department
You didn't try to see what happens with AAC sheet did you?
Regards dave
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Last edited by cobblerdave; 05-06-2014 at 05:23 AM.
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Old 05-05-2014, 10:24 PM
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Default Re: Vermicrete or Perlcrete as last layer

No, but I would expect it would be the same, AAC, or Hebel is made from Portland after all. Be careful with fibro though, I think it may explode. Next time your wife is not in the house, put a really dry lump of the Hebel on one of the electric stove hotplates turned up full and leave it for around half an hour, taking temps on the cool side every 5 mins or so. Turn off the hot plate and turn the lump over and record the hot side temp with an IR gun, it should reach over 400 C. Turn it back over again recording the temps periodically on the cooler side it drops back to ambient.

Last edited by david s; 05-06-2014 at 03:19 AM.
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Old 05-06-2014, 05:21 AM
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Default Re: Vermicrete or Perlcrete as last layer

G'day Davids
The child bride will put up with a lot of things but after 30 yrs marriage I'm still
not gutsy enough to invading her kitchen with WFO experiments.
I'm still interested in trying this though... But I think I'll retire this one, quietly to the gas BBQ.... A mans still got to eat day to day!
Regards
Dave
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