#11  
Old 10-06-2011, 06:12 PM
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Default Re: Crumbly Vermiculite/Portland Cement

I have been using Vermiculite/Portland for many years as a swimming pool base.
Is this the same product you guys are using?
It comes in bags already mixed. Not very expensive either.
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  #12  
Old 10-06-2011, 10:24 PM
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Default Re: Crumbly Vermiculite/Portland Cement

Could you describe the grain size and characteristics of the mix you use buckeye? Does it absorb a lot of water, more than a standard bagged premix concrete? How would you describe it once it's set?
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Old 10-07-2011, 02:31 PM
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Default Re: Crumbly Vermiculite/Portland Cement

Vermiculite/Portland cement concrete 5:1 mix will support up to one hundred pounds per square inch.
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Old 10-07-2011, 08:55 PM
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Default Re: Crumbly Vermiculite/Portland Cement

Quote:
Originally Posted by benguilford View Post
Could you describe the grain size and characteristics of the mix you use buckeye? Does it absorb a lot of water, more than a standard bagged premix concrete? How would you describe it once it's set?

Could you describe the grain size - I used medium grade it comes in fine medium and coarse- coarse is about the size of a bb for bb gun or a bit larger. medium is 1/2 that size and smaller, not sure what fine looks like.



Does it absorb a lot of water
- Yes, I made 6:1 batches of 3 cu/ft of vermiculite, mixed in 2 gallons of water into the vermiculite and then added the 1/2 cu ft of portland slurry (portland and a half gallon of water) dirzzled over the wetted vermiculite while mixing in with a shovel.

Sets similar to a wine bottle cork.
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Old 10-07-2011, 09:20 PM
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Default Re: Crumbly Vermiculite/Portland Cement

I prefer using vermiculite to perlite because I don't like the dust the perlite contains. I've tried coarse, medium and fine vermiculite and generally prefer the medium grade. They all seem to be about the same density but the fine vermiculite needs more water in the mix. I tried a 50/50 vermiculite, perlite mix with 10% by volume cement and for some reason this brew proved to be the best yet, I will continue using it.I should think the vermiculite and perlite vary considerably depending where it's from and how it's processed.

Last edited by david s; 10-07-2011 at 09:22 PM.
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Old 10-08-2011, 10:04 PM
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Default 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
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Old 10-09-2011, 10:27 AM
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Default 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??
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Old 10-09-2011, 10:55 AM
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Default 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.
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Old 10-09-2011, 11:47 AM
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Default 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.
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Old 10-09-2011, 04:54 PM
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Default 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.
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