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Vermicilite /Cement ratio - Forno Bravo Forum: The Wood-Fired Oven Community

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I'm Peter Reinhart! Ask Me Anything! Monday, February 15, 2016 7:00-8:00 pm EST

To kick off our AMA feature, we have invited author, chef and master bread maker and host of Pizza Quest, Peter Reinhart, to be our first host! Peter will be in the Forum on Monday, February 15th, from 7:00 - 8:00 pm EST. If you are unable to be online during the live session, you can post your questions in the sticky post. Peter will answer those questions during the live session on February 15th. You can view Peter's answers to your questions as well as what happened during the live session in the session thread.

Ask Me Anything New Forum Feature

You will notice a new forum at the top of the main page called, "Ask Me Anything". This forum will be used for live one hour "Ask Me Anything" (AMA) sessions hosted by people who are knowledgeable in different areas pertaining to wood fired ovens. How it works:
- Each AMA will have a "sticky" thread where the community can post questions they would like answered during the live session. This will allow everyone to participate even if you can't be online for the live session. These questions will not be answered by the host until the live AMA; if you need an answer quickly, you should post it in the appropriate Forum area for the community to respond.
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Vermicilite /Cement ratio

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  • Vermicilite /Cement ratio

    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?

  • #2
    Insulating concrete

    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
    Pizza Ovens
    Outdoor Fireplaces

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    • #3
      Mix

      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
      "Made are tools, and born are hands"--William Blake, 1757-1827

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      • #4
        vermic/cement

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

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        • #5
          Re: Vermicilite /Cement ratio

          hi guys , i'm mixing my vermiculite base this weekend, do i use "ordinary" cement for the mix or do i need to use heat proof cement ??? cheers for any feedback ...Dave..

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          • #6
            Re: Vermicilite /Cement ratio

            Ordinary cement..

            Big tip, soak the vermiculite first.. worked a treat when i did mine..

            And i just added cement till it felt right, think it ended up around 4-1 or 5-1

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            • #7
              Re: Vermicilite /Cement ratio

              As Canuck Jim says, mix it gently by hand. You don't want to break up the vermiculite particles thus increasing the density and reducing the insulating value.

              I suggest a 6:1 mix under the hearth and a 12:1 mix for over the dome.
              Last edited by Neil2; 06-07-2011, 07:03 PM.

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              • #8
                Re: Vermicilite /Cement ratio

                Careful you don't add too much water or it will wash the cement off the vermiculite and sit in the bottom of your barrow/container. I've found 10:3.5 by volume of vermiculite, water works well and for the really fine stuff go to 10:4
                Kindled with zeal and fired with passion.

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