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High Heat Mortar Mix question - Forno Bravo Forum: The Wood-Fired Oven Community

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High Heat Mortar Mix question

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  • High Heat Mortar Mix question

    Hello, I have conflicting formulas (by different dealers/people etc..)
    One mix is this:
    1 part cement, 1 part fireclay
    another is:
    1 part cement, 1 part fireclay, 10-12 parts sand

    Seems like an awful big difference in mixes, or is it just me???

  • #2
    Re: High Heat Mortar Mix question

    Here's the high heat mortar primer, which gives two recipes:

    http://www.fornobravo.com/pompeii_ov...at_mortar.html

    My advice? If you have any leeway in your budget, spend it on a dry refractory mortar mix like Heat-stop, or the Ref-mix that FB sells. It's closely matched to the expansion of the firebricks, and doesn't use portland cement, which isn't fire resistant. As a bonus, it's easy to work with. Heat-stop mixes and spreads like peanut butter.
    My geodesic oven project: part 1, part 2

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    • #3
      Re: High Heat Mortar Mix question

      Thats an interesting fire clay mix I have never used lime..
      1-2-6 is what I use.

      1-Clay
      2-cement
      6-sand

      Where did the recipe on the primer page come from? Id be interested in the reasoning..sound like some seriously sticky stuff.. which for this build is defiantly a good thing.
      http://www.palmisanoconcrete.com

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      • #4
        Re: High Heat Mortar Mix question

        From what I am told the hydrated lime adds stickiness to the mortar in its uncured state and that it sets a little softer and responds to expansion and contraction slightly different. I have also heard that hydrated lime fluxes at a different temperature than that of the portland so when the portland is gone the lime is still there.
        The mixture I used for my oven 1/3/1/1, portland/sand/fireclay/lime and that was given me by the grandson of an oven/heater mason from Czechoslovakia.
        Any way that is my 2 cents!
        "Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. " Charles Mingus
        "Build at least two brick ovens...one to make all the mistakes on and the other to be just like you dreamed of!" Dutch

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        • #5
          Re: High Heat Mortar Mix question

          From what I've read you should avoid portland cement in the mortar mix but use calcium aluminate.

          Calucem the manufacturers of Lumnite gave me the following mix.

          2 sand
          2 Calcium Aluminate
          1 Fire Clay

          I used this for the chimney because I ran out of Refmix. It is quite difficult to used except in very small batches. Seems to go off in about 15 minutes.

          if you can justify the cost I would highly recommend Refmix

          You can check out Calucem on the web, give them a call they're very helpful

          http://www.calucem.com/

          Hope this helps

          Rgds

          Balty

          Comment


          • #6
            Re: High Heat Mortar Mix question

            Definitely if you can get calcium aluminate it will be better...it is a bit harder to find however. It will also set sooner and harder than a portland mix and cannot be rehydrated so for a novice bricklayer it will be important to mix small batches so as not to waste it. It will be a bit more difficult to knock apart once the mortar has set a bit but, hopefully you won't have to be concerned with that.
            Best
            Dutch
            "Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. " Charles Mingus
            "Build at least two brick ovens...one to make all the mistakes on and the other to be just like you dreamed of!" Dutch

            Comment


            • #7
              Re: High Heat Mortar Mix question

              Tried a small batch of the 2-2-1 and much better, a little stickier...though still very firm, meaning that when the mortar hits the bricks, it really gets firm fast. I may need to wet them down harder....seems like I can't mash any extra out, making the leveling up difficult.
              Trying to learn what I can about flours, fermentation and flames...

              My 81 inch first build; http://www.fornobravo.com/forum/f37/...ost-11354.html

              My 52 inch mobile; http://www.fornobravo.com/forum/f37/...ing-20874.html

              our FB page; https://www.facebook.com/pages/Artys...20079718042660

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              • #8
                Re: High Heat Mortar Mix question

                Wind...
                calcium aluminate on ebay.... Secar 71 Calcium Aluminate Cement Refractory - eBay (item 140352762915 end time Jun-13-10 06:52:31 PDT)

                Comment


                • #9
                  Re: High Heat Mortar Mix question

                  $24 plus shipping for 10lbs!!...that comes out to $215 per bag and I have 7 bags of alum silc to sell if I can't get this recipe to work out...I may go to Lars formula and just use portland.
                  Trying to learn what I can about flours, fermentation and flames...

                  My 81 inch first build; http://www.fornobravo.com/forum/f37/...ost-11354.html

                  My 52 inch mobile; http://www.fornobravo.com/forum/f37/...ing-20874.html

                  our FB page; https://www.facebook.com/pages/Artys...20079718042660

                  Comment


                  • #10
                    Re: High Heat Mortar Mix question

                    I would not buy the stuff on Ebay because it has a short shelf life- about 6 months. You could get it and find that it's already gone off. Buy it from a reputable refractory supplier. It is expensive and tricky to work with- it goes off fast and is quite temperature dependent
                    Kindled with zeal and fired with passion.

                    Comment


                    • #11
                      Re: High Heat Mortar Mix question

                      Originally posted by david s View Post
                      I would not buy the stuff on Ebay because it has a short shelf life- about 6 months. You could get it and find that it's already gone off. Buy it from a reputable refractory supplier. It is expensive and tricky to work with- it goes off fast and is quite temperature dependent
                      David, do you have some recipes for me to try? I am dissapointed in my alum sil cement for lack of stickiness and diffucult to work-i-ness..
                      Trying to learn what I can about flours, fermentation and flames...

                      My 81 inch first build; http://www.fornobravo.com/forum/f37/...ost-11354.html

                      My 52 inch mobile; http://www.fornobravo.com/forum/f37/...ing-20874.html

                      our FB page; https://www.facebook.com/pages/Artys...20079718042660

                      Comment


                      • #12
                        Re: High Heat Mortar Mix question

                        Try the poor mans mix 3:1:1:1 sand, portland cement, lime, fire clay. But be careful the lime is particularly drying on the hands, you end up losing a layer of skin. Use rubber gloves and or barrier cream.
                        Kindled with zeal and fired with passion.

                        Comment


                        • #13
                          Re: High Heat Mortar Mix question

                          That blend does work with portland, but not with alum sil, the lime is a no-no and sets it off in just a few (2-3) minutes..
                          Trying to learn what I can about flours, fermentation and flames...

                          My 81 inch first build; http://www.fornobravo.com/forum/f37/...ost-11354.html

                          My 52 inch mobile; http://www.fornobravo.com/forum/f37/...ing-20874.html

                          our FB page; https://www.facebook.com/pages/Artys...20079718042660

                          Comment


                          • #14
                            Re: High Heat Mortar Mix question

                            The lime also acts as an accelerant with calcium silicate cement. Because the stuff is expensive it is a waste if it goes off too fast.
                            Kindled with zeal and fired with passion.

                            Comment


                            • #15
                              Re: High Heat Mortar Mix question

                              Finally, success! After a long discussion with the US rep for the REFCON MG by Calcem, I was pointed in the right direction, 2 issues were giving me fits; lack of stickiness and short "pot time, or work time".
                              1) lime is the enemy of aluminum silicate based cements, the residue in my work tools was enough to set it off in 3 to 5 minutes, and the Forno Bravo formula posted as adding one part lime is REALLY off base. Bought a new tub, trowel and fresh blending buckets..now "work time" is as long as I need. No more lime contamination.
                              2) stickiness was a function of adding more sand for more "surface area" to hold the water. I also tried his tip of adding a few drops of dish soap to entrain air...not sure if that helped or not...so the mixture I am using to lay (soaked) brick; 6 sand, 2 cement, 1 clay. I may even drop cement to 1 part when I parge the outside of the dome.

                              thanks guys
                              Trying to learn what I can about flours, fermentation and flames...

                              My 81 inch first build; http://www.fornobravo.com/forum/f37/...ost-11354.html

                              My 52 inch mobile; http://www.fornobravo.com/forum/f37/...ing-20874.html

                              our FB page; https://www.facebook.com/pages/Artys...20079718042660

                              Comment

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