Vermicrete Ratio Clarity

[Spinal]

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 vermiculiteortland; 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]

Re: 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 vermiculiteortland; 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]

Re: Vermicrete Ratio Clarity

Cool - volume it is, and 5:1

Thanks!

[Tscarborough]

Re: Vermicrete Ratio Clarity

FYI, 94# portland cement = 1 CuFt.

[Neil2]

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]

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]

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]

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]

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]

Re: Vermicrete Ratio Clarity

Thanks guys. I feel comfortable installing vermicrete under my stainless entryway floor now.

[Spinal]

Re: Vermicrete Ratio Clarity

Great - thanks

Vermiclete slab went down yesterday - now I'm waiting for the lot (concrete & vermicrete) to cure; then a week of drying of the vermicrete before I continue the build!

M.

[david s]

Re: Vermicrete Ratio Clarity

Good plan.