Vermicilite /Cement ratio

[Fudugazi]

I am mixing my cement with 3 to 1 cement gravel mix to Portland cement. How much Vermiculite should I add to this mix to optimize the insulating value of the Hearth?

[james]

Ciao Fudugazi,

The insulating concrete is 5-6 parts of vermiculite to 1 part portland cement. The vermiculite is the only aggregate, so in that sense, you are not adding vermiculite to redi-mix concrete (where sand and gravel are the aggregate).

Any easy way of doing this is to mix the vermiculite and portland together (where the portland coats the vermiculite) when they are dry, then you add water until you get an oatmeal texture. I have heard that mechanical mixers can beat up the vermiculite and ruin the hole structure.

The mixture is light, and easy to work with. It's also cheap and efficient.
James

[CanuckJim]

James,

Just a back up here. Six to one is the ratio I'd use, and no ready mix. A mechanical mixer will beat up the vermic way too much. Mix it dry, then add water. The resulting wet mix is light and easy to work with, the lightest in the entire project.

Jim

[Fudugazi]

Thanks guys Got it The mixture gets poured this weekend on Lake of The Woods!!!! Ciao Fudugazi