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Heat stop premixed mortar

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  • #16
    Re: Heat stop premixed mortar

    Originally posted by NCMan View Post
    .....Do you think that the 4" of Perlcrete under the hearth floor is fine? I know more is better, but elevation wise, 4" works.
    I think that 4" of perlite (no greater than 5 to 1) will work great! as long as it is allowed to, and and also kept dry .
    Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build

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    • #17
      Re: Heat stop premixed mortar

      Ok, thanks. I was planning on a 4:1 or so and will use a vapor barrier between the slab and it. Also, will do my best to keep it all dry.
      My Build:
      http://www.fornobravo.com/forum/f8/s...ina-20363.html

      "Believe that you can and you're halfway there".

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      • #18
        Re: Heat stop premixed mortar

        You can go leaner for a greater insulating value.
        Old World Stone & Garden

        Current WFO build - Dry Stone Base & Gothic Vault

        When we build, let us think that we build for ever.
        John Ruskin

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        • #19
          Re: Heat stop premixed mortar

          By "leaner", I'm assuming you mean more Portland and less Perlite? Or the other way? I'm not real familiar w/that term, although I've heard it before. Some people use that term differently. Since the Perlite "slab" will be holding up the entire weight of the oven, I want it to be able do so effectively. What ratio are you proposing, just so I understand you correctly? And thanks for helping a greenhorn.
          My Build:
          http://www.fornobravo.com/forum/f8/s...ina-20363.html

          "Believe that you can and you're halfway there".

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          • #20
            Re: Heat stop premixed mortar

            Originally posted by NCMan View Post
            By "leaner", I'm assuming you mean more Portland and less Perlite? Or the other way? I'm not real familiar w/that term, although I've heard it before. Some people use that term differently. Since the Perlite "slab" will be holding up the entire weight of the oven, I want it to be able do so effectively. What ratio are you proposing, just so I understand you correctly? And thanks for helping a greenhorn.
            A lean mix in masonry refers to less portland or binder to aggregate. Perlite or vermiculite is the aggregate in an insulating mix. I went 5 or 6 :1 on all my builds. Tscar had some kind of compression value chart he posted at one time, I don't have it though. But I'm pretty sure you would be ok at 8:1
            Old World Stone & Garden

            Current WFO build - Dry Stone Base & Gothic Vault

            When we build, let us think that we build for ever.
            John Ruskin

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            • #21
              Re: Heat stop premixed mortar

              Ok, thanks for the explanation. I'd like to obviously have it be strong enough to hold the weight, but get as much insulation value as I can. I'll go with either 5 or 6 for now. I'll also try and find that info from TScar. I know more is better, but in your personal opinion, is 4" sufficient? That elevation works best for us, but if it makes a huge difference, I could go a bit thicker. Perhaps going leaner helps make up for the thickness, thereby raising the R value (?) So, say if I stuck w/the 4" thickness, but went leaner to say, 5 or 6:1, it makes a good bit of difference, if I follow you right. Makes sense to me. I've never worked w/this material, it's all new to me. I appreciate your info.
              My Build:
              http://www.fornobravo.com/forum/f8/s...ina-20363.html

              "Believe that you can and you're halfway there".

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              • #22
                Re: Heat stop premixed mortar

                Also, if I remember correctly from earlier reading, the components should be thoroughly dry mixed prior to adding the water, right?
                My Build:
                http://www.fornobravo.com/forum/f8/s...ina-20363.html

                "Believe that you can and you're halfway there".

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                • #23
                  Re: Heat stop premixed mortar

                  That the way it's normally done...avoids the portland getting clumps.
                  Old World Stone & Garden

                  Current WFO build - Dry Stone Base & Gothic Vault

                  When we build, let us think that we build for ever.
                  John Ruskin

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                  • #24
                    Re: Heat stop premixed mortar

                    I would assume that. Everything else I ever mixed was dry mixed. Just wanted to be sure. And try to fold it over when mixing to avoid chopping it all up, right?
                    My Build:
                    http://www.fornobravo.com/forum/f8/s...ina-20363.html

                    "Believe that you can and you're halfway there".

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                    • #25
                      Re: Heat stop premixed mortar

                      Yes...........
                      Old World Stone & Garden

                      Current WFO build - Dry Stone Base & Gothic Vault

                      When we build, let us think that we build for ever.
                      John Ruskin

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                      • #26
                        Re: Heat stop premixed mortar

                        Thanks for the help. I will probably get around to getting some Perlite and Portland this week after I raise up the forms. I'm still not sure if I want to go thicker yet. I'll probably stick to 3.5" and mix it at a 5 or 6:1. Once I mix it all up, get it in, etc., is there any advantage to covering it up for awhile,or not? I still have the slab covered (it's still as green as the day it was poured) and will keep the moisture barrier in between the two "slabs".
                        My Build:
                        http://www.fornobravo.com/forum/f8/s...ina-20363.html

                        "Believe that you can and you're halfway there".

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                        • #27
                          Re: Heat stop premixed mortar

                          I would only cover for a day or so, then let the sir and sun start working on it.
                          Old World Stone & Garden

                          Current WFO build - Dry Stone Base & Gothic Vault

                          When we build, let us think that we build for ever.
                          John Ruskin

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                          • #28
                            Re: Heat stop premixed mortar

                            Ok. Thanks again. How long, in your opinion, should I allow the Perlite dry and air out before I start building on it? I know temps, etc come into play, but on average, how long is long enough? I'm not in a hurry, just anxious.
                            My Build:
                            http://www.fornobravo.com/forum/f8/s...ina-20363.html

                            "Believe that you can and you're halfway there".

                            Comment


                            • #29
                              Re: Heat stop premixed mortar

                              A week or so. Sooner if you leave the form on.
                              Old World Stone & Garden

                              Current WFO build - Dry Stone Base & Gothic Vault

                              When we build, let us think that we build for ever.
                              John Ruskin

                              Comment


                              • #30
                                Re: Heat stop premixed mortar

                                A lean mix in masonry refers to less portland or binder to aggregate. Perlite or vermiculite is the aggregate in an insulating mix. I went 5 or 6 :1 on all my builds. Tscar had some kind of compression value chart he posted at one time, I don't have it though. But I'm pretty sure you would be ok at 8:1
                                I agree. I went with an 8:1 vermicrete 'slab', mostly because it was right in the middle of the ratios (4:1 - 12:1) reported here. After installing the vermicrete under 2" of CF board, I placed some of the last batch surplus into a round butter container and let it dry (3 days).

                                Even at 8:1, the test 'disk' (6" diameter by 1" thick) was surprisingly rigid and very difficult to compress with my thumb. It had the consistency of one of those puffed rice crackers. I could break an edge off quite easily, but when I placed an 8x8x16 CMU on top of the disk edgewise, it didn't budge.

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