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-   -   Vermicrete Ratio Clarity (http://www.fornobravo.com/forum/f28/vermicrete-ratio-clarity-18210.html)

Spinal 08-11-2012 04:43 AM

Vermicrete Ratio Clarity
 
Right... I need a little clarity before a f**k up...

Vermicrete... I'm reading ratios from 5:1 all the way to 20:1 for vermiculite:portland; which is fair enough. What would people suggest?

Secondly, are the ratio by volume or weight? The vermiculite here is sold by volume, but the portland by weight. So if it's volume, how many litres is a 20kg bag of portland cement?

M.

Gulf 08-11-2012 05:40 AM

Re: Vermicrete Ratio Clarity
 
Quote:

Originally Posted by Spinal (Post 136455)
Right... I need a little clarity before a f**k up...

Vermicrete... I'm reading ratios from 5:1 all the way to 20:1 for vermiculite:portland; which is fair enough. What would people suggest?

Secondly, are the ratio by volume or weight? The vermiculite here is sold by volume, but the portland by weight. So if it's volume, how many litres is a 20kg bag of portland cement?

M.

5:1 is recomended for under the floor and dome. 10:1 is most often recomended for insulation over the dome.

The ratios are by volume.

I cant help you on the metric system, but I wouldn't get hung up on Pi-R-Squaring too much. If you use the same or equal size containers to measure the volume of each , you will be OK :).

Spinal 08-11-2012 05:44 AM

Re: Vermicrete Ratio Clarity
 
Cool - volume it is, and 5:1 :)

Thanks!

Tscarborough 08-11-2012 06:52 AM

Re: Vermicrete Ratio Clarity
 
FYI, 94# portland cement = 1 CuFt.

Neil2 08-11-2012 11:45 AM

Re: Vermicrete Ratio Clarity
 
5:1 for under the floor to provide a higher compressive strength for supporting the weight (and still provide adequate insulation).

For over the dome, where high strength is not needed, use as little cement in the mix as possible. The lower the cement content the higher the insulation value. The recommended ratio is in the order of 10:1 or 12:1.

david s 08-11-2012 04:17 PM

Re: Vermicrete Ratio Clarity
 
Expect about a 14% reduction in volume once mixed with water and cement. Mix by hand, not in a mixer, to reduce this problem.

GianniFocaccia 08-11-2012 04:23 PM

Re: Vermicrete Ratio Clarity
 
Since portland tends to break down from thermal cycling at around 500F, how do the prescribed ratios (5:1 under-floor, 10:1 on-top-of-dome) respond to the tempertures radiating from below and above an oven?

david s 08-11-2012 04:33 PM

Re: Vermicrete Ratio Clarity
 
The outside temp of the dome or floor brick will be lower so it should only be the vermicrete in direct contact withe the brick that would be experiencing temperatures that would be damaging to the Portland. Of course if you have blanket between them the temperature would be way lower. If anyone demolishes an oven or removes floor bricks, tell us what the vermicrete looks like.

Tscarborough 08-11-2012 04:47 PM

Re: Vermicrete Ratio Clarity
 
Well, I have fired a 1400 degree gun at perlcrete 6-1 for about 15 minutes, and other than glowing red hot there was no degradation (or heat transfer through 3"). The heat degradation that takes place is basically a reversal of the process that hydration of portland cement creates, i.e. it will return to powder. That is aside from the effects of aggregates, which are not normally used in perlcrete anyway.

Short answer: Intermittent indirect heat of 500-800 degrees will not destroy portland mixes in the short term. Direct flame temps WILL.

GianniFocaccia 08-11-2012 06:42 PM

Re: Vermicrete Ratio Clarity
 
Thanks guys. I feel comfortable installing vermicrete under my stainless entryway floor now.


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