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Corner Pompei Oven following Forno Bravo instructions-Loei Thailand

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  • #16
    This doc may be of some use to you.

    Vermicrete insulating slab PDF copy.pdf
    Kindled with zeal and fired with passion.

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    • #17
      Originally posted by david s View Post
      This doc may be of some use to you.

      [ATTACH]n453547[/ATTACH]
      Very informative, indeed. Thank you very much.

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      • #18
        Not sure if you poured your v-Crete yet but I went with a 8-9 : 1 ratio for my v-Crete gave it it a light compaction and it turned out great for me better insulation properties then 5:1 too I know a few builders here have gone as high as 10 : 1

        dry mix first then slowly add your water as well keep it dry!

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        • #19
          Originally posted by Mr.Pizza3 View Post
          Not sure if you poured your v-Crete yet, but I went with an 8-9 : 1 ratio for my v-Crete gave it is a light compaction, and it turned out great for me better insulation properties then 5:1 too I know a few builders here have gone as high as 10 : 1

          dry mix first then slowly add your water as well, keep it dry!
          Many thanks, I unfortunately already poured two bags, but it appeared to be not sufficient. The vermiculite I found did have lots of broken kernels and dust, also I suspect the seller to fill the bags by weight and not by volume. The volume I calculated was 150 litres, and two 100-litre bags did not fill it...
          I guess it's 8:1:2 eight volumes of vermiculite, one of Portland and two of water to have enough water for the chemical reaction.
          In the meantime, I prepared the bricks for the oven floor. If there are spaces, can I pour refractory cast concrete, or refractory clay?
          For the formwork, 'KISS', four F clamps, four planks and the scraps from the template cutout to hold the circle in place. A cast aluminium water level that has followed me faithfully for more than 45 years...

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          • #20
            The sand/clay levelling mix is better left dry because if a floor brick needs to be replaced at a later date, the wet mix sets very hard like mortar, but the dry mix will not. It allows for expansion and contraction of individual bricks.
            Most builder recommend a 5:1 vermicrete for the under floor insulation mix because of the weight it has to support. A 10:1 mix over the dome is more suitable though because it only needs to be firm enough to stucco against.
            . The accompanying table shows relative strength and insulation values which explains the appropriate ratio for under or over the oven.
            Click image for larger version

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            Kindled with zeal and fired with passion.

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            • #21
              My plan for the spaces was to either back fill with a dry clay sand mixture or just let the ash slowly fill in the floor

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              • #22
                More on vermiculite ratios here

                https://community.fornobravo.com/for...e-cement-ratio

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                • #23
                  Originally posted by david s View Post
                  The sand/clay levelling mix is better left dry because if a floor brick needs to be replaced at a later date, the wet mix sets very hard like mortar, but the dry mix will not. It allows for expansion and contraction of individual bricks.
                  Thanks, David, I was about to fall into the trap...
                  What should be the sand/clay mix ratio?
                  Does it make sense to cut the bricks on the fly?
                  I initially placed my bricks on my parking floor and marked the shape using the template I made for the vermiculite insulation mix, but I fear the bricks will not fit the same way once in place if I cut them in advance.
                  Last edited by Garouda; 07-26-2023, 10:55 PM.

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                  • #24
                    As the diameter of each row decreases as the dome rises, the angles that need to be cut get greater. If you own a wet saw this isn’t a problem, but if you have to hire one it is.
                    Kindled with zeal and fired with passion.

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                    • #25
                      Originally posted by david s View Post
                      As the diameter of each row decreases as the dome rises, the angles that need to be cut get greater. If you own a wet saw this isn’t a problem, but if you have to hire one it is.
                      Thanks, but I meant the oven floor, I am not that far.

                      By the way, what sand/clay mix ratio do you recommend for the levelling layer between the floor bricks and the vermiculite insulation? Thanks.

                      I used the forum search engine and found numerous variations
                      1:1 and water
                      but I will follow your advice and won't use water
                      2:1 and even 3:1, on another website it was 2-4 sand :1 fire clay
                      someone on this forum mentioned having problems with the 1 :1 ratio
                      "03-19-2014, 01:26 AM
                      Re: 42" Started in Fountain Hills, Arizona

                      Also, some people have mentioned having difficulty with 1:1 ratio of fire clay:sand for the levelling of the hearth brick. You can make a leaner mix with no ill effects, the clay is there to add some adhesion when setting the brick, little more."
                      Last edited by Garouda; 07-27-2023, 10:43 PM.

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                      • #26
                        50/50 by volume dry fine sand and powdered clay.If the mix is wet a 50/50 mix will be too sticky and difficult to apply. It will also stick like crazy making any brick removal very difficult later if that is required. If used dry this is not a problem and being loose allows free movement of individual bricks that will have uneven thermal expansion. The finer clay particles fill the air spaces between the sand grains, reducing their movement and creating a denser layer.
                        Last edited by david s; 07-28-2023, 05:48 PM.
                        Kindled with zeal and fired with passion.

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                        • #27
                          Originally posted by david s View Post
                          50/50 by volume dry fine sand and powdered clay.
                          Very reactive, thanks a lot...

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                          • #28

                            The sun is back so I can use my power tools without turning on my diesel generator...
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                            • #29
                              Today I made a simple, indispensable tool. Note the thin piece of wood to mark the length, this avoids all problems caused by angles. KISS.

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                              • #30
                                A couple comments on the IT. The pivot point should be at the floor level or as close as possible. This changes the dimension of the oven OD as you move up. Not a deal killer just something you need to be aware of and adjust as needed. Most important design issue is the pivot point along the wood stick needs to intersect the center of the dome brick. This makes the internal brick face perpendicular to the center of the floor. The error by the current set up is cumulative as you go up and causes the brick edge to start form a stepped edge. Last, make the wood rod adjustable in length is very helpful in adjusting for irregularities.
                                Russell
                                Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]

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