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Post by Donkey on Mar 17, 2014 23:09:52 GMT -8
Watch where the fly-ash comes from. It's often waste from industrial flues, which are full of heavy metals and other toxins.
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Post by patamos on Mar 18, 2014 10:55:51 GMT -8
Magnesium in the concrete mix holds promise. NOt sure what the best recipe is but typically the drier the better. From what i have read here and there the concrete in those old Roman collussiums (sp?) and great walls of china had a fairly high mag content and were tamped more than poured.
In considering specific heat capacity, conductivity, emissivity etc... i hear granite is a distant second to soapstone, but still about double that of most fire bricks, and more than double that of common red bricks. That said, my experience in having a 1.5 granite cook surface/slab above the 6" dia. heat riser in a 6" rocket oven crack shortly after first fire up... tells me that it is not ideal for the high temps.
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Post by pinhead on Mar 18, 2014 12:43:46 GMT -8
That said, my experience in having a 1.5 granite cook surface/slab above the 6" dia. heat riser in a 6" rocket oven crack shortly after first fire up... tells me that it is not ideal for the high temps. I can say with confidence that the crack in the granite slab wasn't due to temperature - it was due to temperature differential. Get a spot in the center of the granite good'n'hot and keep the outside edges cool and you're bound to get cracking. Thermal ShockThermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. |
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Post by talltuk on Mar 18, 2014 13:07:07 GMT -8
Watch where the fly-ash comes from. It's often waste from industrial flues, which are full of heavy metals and other toxins. Ta mate. I will definitely look into that when the time comes. |
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Post by patamos on Mar 19, 2014 9:24:39 GMT -8
That said, my experience in having a 1.5 granite cook surface/slab above the 6" dia. heat riser in a 6" rocket oven crack shortly after first fire up... tells me that it is not ideal for the high temps. I can say with confidence that the crack in the granite slab wasn't due to temperature - it was due to temperature differential. Get a spot in the center of the granite good'n'hot and keep the outside edges cool and you're bound to get cracking. Thermal ShockThermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. Thanks for the clarification Pinhead. Ya, there was also an irregular seam in the slab which probably let go first. I switched to a reclaimed pottery kiln shelf and it has held up fine. |
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Post by patamos on Mar 19, 2014 10:26:29 GMT -8
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Post by 2tranceform on Mar 19, 2014 12:00:03 GMT -8
Great article Patamos! Thanks for sharing. There is atleast one error in it though. Modern batteries placed on concrete do not discharge more rapidly. They are made with much better insulating materials than in the past. "They don't make them like that anymore," is a good thing in this case. Interesting though.  |
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Post by patamos on Mar 19, 2014 15:50:45 GMT -8
Thanks Trans,
I've been looking into magnesium drywall boards as a healthier alternative to gyproc in conventional stud frame house builds. And even to use as permanent interior forms and finish plaster substrate when building with stud frames and light clay chip 'n slip infill.
A friend i Ccd the article to has also mentioned a few inaccuracies about the development and patenting of Portland cement, not to mention the lousy grammar. So, reader beware...
But the info about historical applications magnesium is consistent with everything else i have come across.
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Post by patamos on Mar 20, 2014 18:06:07 GMT -8
Further feedback from said friend: The part about concrete 'isotopes' seems inaccurate as well. I know the ionic bahaviour of clay has been well researched and some basic facts established. I wonder if something similar is out there regarding magnesium rich cements? If there is any or much truth in the article about magnesium's binding capacity and health enhancing ionic behaviour... then i'd be very interested in casting big 24"x24"x2" slabs with it to use as bench bell tops.
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