#1  
Old 07-02-2009, 09:00 AM
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Join Date: Oct 2008
Location: CT
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Default vermiculite

I recently called a masonry supply house to see if they carried vermiculite. They said that the vermiculite I need is called "attic vermiculite" which is bigger in size than the standard (plant and garden) vermiculite that they and other home centers carry. Is this true and also when mixing with portland cement that I need to add sand so the finished insulated pad will not crumble. Need some info please. Does the portland cement that a Home Depot or Lowes carries have sand already mixed in (premix Quickrete). Am pouring the hearth tomorrow and would like to get my supplies ASAP. Also how much vermiculite is needed per bag.
G
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  #2  
Old 07-02-2009, 11:09 AM
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Default Re: vermiculite

Quote:
They said that the vermiculite I need is called "attic vermiculite" which is bigger in size than the standard (plant and garden) vermiculite that they and other home centers carry.
No. This domestic insulation vermiculite is treated with silicone to prevent it from absorbing water, and doesn't mix with the portland well. You need regular agricultural vermiculite. Particle size doesn't matter.

Quote:
when mixing with portland cement that I need to add sand so the finished insulated pad will not crumble
No! No! No! the vermiculite is the only aggregate in insulating concrete! Sand is not an insulator, and this won't work at all.

Quote:
Does the portland cement that a Home Depot or Lowes carries have sand already mixed in (premix Quickrete)
No! Two different things. You want portland cement, not concrete or mortar mix. Portland is the active ingredent in concrete, and you're making concrete with a lightweight aggregate, instead of sand and gravel.
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  #3  
Old 07-02-2009, 11:52 AM
Apprentice
 
Join Date: Oct 2008
Location: CT
Posts: 168
Default Re: vermiculite

Great advice. I really appreciate the info. I was a little suspect when I got off the phone with the person from masonry supplies and you have certainly made it all clear. There is a large grower in the area that I know and I am going to hit him up for the vermiculite. It will be a pizza trade for vermiculite deal if I'm lucky (haha).
Thanks again and hopefully I can get through with the hearth pour tommorrow and think about laying out the insulating pour soon after it cures.
G
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