Crumbly Vermiculite/Portland Cement

[benguilford]

Re: Crumbly Vermiculite/Portland Cement

Has anyone else tried the 'sealed perlite' that I mentioned previously? I agree with you David about the dust - had to wear a mask the throughout the mixing phase until it was fully wetted out, that stuff is evil! But I was really happy with the finished result, nothing like a wine bottle cork, this was a proper, rock hard concrete. Interested to hear if anyone else has done something similar

[buckeyebreadman]

Re: Crumbly Vermiculite/Portland Cement

Ben, The premix I get is probably medium....I agree with the characteristics mrchipster posted....
It also seems to have some gold flecks in it.....is this normally what Vermiculite looks like??

[Tscarborough]

Re: Crumbly Vermiculite/Portland Cement

Most perlite you will have access to is siliconized, as it is designed to be used as loose fill insulation. If you get perlite from an agricultural source, it will most likely not be siliconized. Either works fine.

[Neil2]

Re: Crumbly Vermiculite/Portland Cement

Like David, I ended up with half perlite, half vermiculite in the mix. I found this was more "workable" in terms of leveling and in shaping for the dome.

That said, either or both will provide the insulation value you want. Go with what is cheapest locally. If the price difference is small, mix it half and half.

[dmun]

Re: Crumbly Vermiculite/Portland Cement

I've heard it said that you shouldn't use the silicone treated perlite, but your explanation makes sense. You can't argue with results.

[benguilford]

Re: Crumbly Vermiculite/Portland Cement

O how I wish I didn not have to work full time, that I could experiment all day long, I could make samples and run tests on them... sighs...

[eatingmorefood]

Re: Crumbly Vermiculite/Portland Cement

Getting ready to add a layer of 50% vermiculite and 50% perlite with cement mixture. Not sure how much cement to the vermiculite and perlite. Planning on a few inches on top of my roof. and a few inches on the sides of my Bella square oven. Entrance and insides are almost done, build pics are located here: http://www.chefdepot.net/woodoven.htm

[Lill Dave]

Re: Crumbly Vermiculite/Portland Cement

I used a 5 to 1 perlite mix that works real good .
Thickness is 3.5 in with a 1 in layer of morter over that.
The outside of my pompaie oven reaches 150 degres so I would advise at least 5 in. of insulation on the outside of the oven.

[eatingmorefood]

Re: Crumbly Vermiculite/Portland Cement

Lil Dave,
thanks for the recipe. You used a 5 to 1 perlite mix that works real good .
Is that 5 parts perlite to 1 part mortar mixed ? Ratio of 5 to 1 by volume?
thanks!
Eatingmorefood

[Lill Dave]

Re: Crumbly Vermiculite/Portland Cement

Not morter cement,mix 5 to 1 dry then add water. It's real important to mix it dry.Yes by volume.
You can also use vermuclite same ratio , same mixing, I'm telling you this because one of these products costs half as much as the other .
I think vermiculite is the less expensive.
Good luck

[Neil2]

Re: Crumbly Vermiculite/Portland Cement

I suggest a 5:1 or so only for the weight bearing layer under the hearth.

For insulation layer, such as over the dome, use a 12:1 mix or so. This will have a much higher insulating value but still be more than firm enough to support any surface finish such as rendering or stucco.

[eatingmorefood]

Re: Crumbly Vermiculite/Portland Cement

over the dome, use a 12:1 mix or so. ..


So then after mixing these 12 parts vermiculite to 1 part cement in wheelbarrel, then add enough water until it is like paper-mache ? Is this correct ? thank you much !

[Neil2]

Re: Crumbly Vermiculite/Portland Cement

"then add enough water until it is like paper-mache ?"

Yes. Mix gently with hand tools. Just enough water so it is "workable" and sort of sticks together is best. The actual water content is not that critical.

[benguilford]

Re: Crumbly Vermiculite/Portland Cement

I find it easiest to mix by hand sometimes, just get some long rubber gloves and get up to your elbows in it! Good times

[eatingmorefood]

Re: Crumbly Vermiculite/Portland Cement

Thank you for the recipe. I will be working it soon.