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  • #16
    Also while the concrete is green (and before you do the perlcrete) drill a few small drain holes through the slab under the oven position. David has been advocating this for a number of years and it helps in the drying process of the perlcrete base insulation pad.
    Mike Stansbury - The Traveling Loafer
    Roseburg, Oregon

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    • #17
      Originally posted by UtahBeehiver View Post
      Those are the correct ratios, 5-1 for base, 8-10 for insulating the dome.
      Thank you Russell. Maybe I read it from one of your older posts

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      • #18
        Originally posted by Monilee View Post
        Iím actually just trying to figure this out myself. Iím pouring the first concrete base slab today. 3Ē concrete. Iím thinking Iíll do another pour over this with a perlite slab(5:1) about 4Ē thick. Then, Iíll figure out what my firebrick layout will be. Suggestions very much appreciated.
        I underestimated my perlite. Well actually I never even bothered to calculate. My base alone needs 200 litres. I have 100 litres here juswt delivered. My diameter is 1600mm and depth is 100mm. I think that is about 200,000 cc (200 litres). That is excluding the entry arch base

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        • #19
          Originally posted by SableSprings View Post
          Also while the concrete is green (and before you do the perlcrete) drill a few small drain holes through the slab under the oven position. David has been advocating this for a number of years and it helps in the drying process of the perlcrete base insulation pad.
          Thank you for the tip SS
          I have no problem with drying as the temperature is 32 C - 35 C every day. Actually I am more worried about the sun, so I will leave the gazebo over it during drying.

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          • #20
            Originally posted by david s View Post

            Because there is so much free water left in a vermicrete slab and it is the hardest to eliminate when doing the drying fires, it is a good idea to pause after casting it to allow the sun and wind to dry it as much as possible before proceeding to build over it. More explanation in my attached experiment.

            [ATTACH]n403610[/ATTACH]
            Thank you David

            I will leave it for at least a week before laying the bricks. This is very much part time, so no problem

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            • #21
              Just ordered the Tandoor. Well I drew the shape and asked them to make it. It is 600mm dia on bottom, 450mm dia on top, and it is 700mm high. It will also have a lid.
              Below is a couple of photos of our local pottery ...

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              • #22
                The perlite base is now complete. I used 300 litres of perlite in the mix with about 60 litres of cement, and that has taken me to about 10mm of the top.

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                • #23
                  This perlite has eaten a big hole in my budget. The shipping is the killer
                  • Perlite 100 L .......... $25.00
                  • Shipping ................ $21.50
                  • 60 hollow blocks ... $19.00
                  • 4 bags Portland .... $18.00
                  • 300 bricks ............. $60.00
                  • 10 bags portland ... $45.00
                  • Perlite 200 L ...........$50.00
                  • Shipping ............... $43.00
                  • Portland ................ $4.50
                  Running total : ................. $286.00

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                  • #24
                    Am wondering about the mortar mix. Cannot get lime. I have a few bags of potters clay (the same stuff they use to make the bricks.
                    Any Ideas?

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                    • #25
                      There are some mortar plasticizers than can be a lime substitute. A Google search shows several.
                      Russell
                      Build Link............... Picassa Photo Album Link

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                      • #26
                        Russell,

                        Although lime can be replaced with substitutes in standard mortar, I'm not so sure that it can be replaced in a refractory mortar. I was involved in a discussion with Tscarborough several years ago about type-N masonry mortar. (It would be great if he would join in on this conversation) The original formula for Type-N masonry cement was 50/50 lime and portland cement. Most all major manufacturers of masonry cement have replaced the lime with crushed limestone and other additives. There are still a few small companies here in the US who make it by the original formula. If there is a manufacturer in the Philippines who makes it by the original formula, it can be used to make home brew.

                        joe watson

                        "A year from now, you will wish that you had started today "

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                        • #27
                          Great point, keep me on track, I was looking more at workability not refractory.............
                          Russell
                          Build Link............... Picassa Photo Album Link

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                          • #28
                            Thank you guys.
                            I have used sand cement lime mix years ago. But the lime was mostly replaced with plasticiser (we used to call mortariser) in the 80's. We even used dish washing liquid to make the mortar 'fatty' or "puffy' and easier to use.
                            So how about using the clay I got from the pottery instead of sand?
                            It is the very same stuff that is used to make the red bricks that I am using

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                            • #29
                              The hydrated lime is a cementious material and capable of withstanding higher temperatures than portland cement.(around 500C as opposed to around 300C). This is its primary function in the home-brew mix. If you replace it with clay which is quite refractory it is not a cementious material although it will set quite hard as in a cob oven. It is really only an extremely fine aggregate. Also the higher proportion of clay in the mix leads to more shrinkage (cracking).
                              Kindled with zeal and fired with passion.

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                              • #30
                                Can I use full glass wine or liquor bottles in the floor under the vermiculite as extra insulation?? I just now got the bags or vermiculite and can finally start my build.
                                Thanks.

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