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vermiculite mix? - Forno Bravo Forum: The Wood-Fired Oven Community



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vermiculite mix?

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  • vermiculite mix?

    I added sand to my portland cement and then added my vermiculite, I'm not sure if this was the correct way to mix? It's been 3 days and it has not dried yet and is very soft and brittle. Should I rip it out and just add the portland to the vermiculite?

  • #2
    Re: vermiculite mix?

    Sand isn't a good idea because it will reduce the insulating properties of the vermiculite, but it shouldn't make a difference in hardening. To the portland, the sand is just another aggregate. I'd wait a week before making any decisions. What proportions did you use?

    Hey, Kenilworth is just next door to me. Welcome.
    My geodesic oven project: part 1, part 2


    • #3
      Re: vermiculite mix?

      I used 20 parts sand to 1 part cement for my mortar mix then i mixed the 5 vermiculite to 1 portland. Idon't really want to rip it out, but i will if i have to. Do you think i will loose much heat?
      Thanks for your help


      • #4
        Re: vermiculite mix?

        If I am reading this correctly, your end result has very little portland cement.
        Basically you have done a 25-1 ratio (aggregate to cement). At this ratio I would be concerned about strength as well as the diminished insulation value.

        Sorry, I have to ask, WHY did you add the sand? where did you get the idea to make a 20-1 mortar as the starting point for your vemiculite concrete? Just curious....I'm pretty certain it was not from anyone on this forum.



        • #5
          Re: vermiculite mix?

          Way too much sand. The correct amount = none. The vermiculite substitutes for the aggregates in concrete, not adds to them. I'm not surprised it isn't hardening.

          Sand (or gravel or broken glass) isn't an insulator. You don't want it in your insulation layer.
          My geodesic oven project: part 1, part 2


          • #6
            Re: vermiculite mix?

            I don't think it's going to set.
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