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Lined or unlined, that is still general purpose concrete sitting directly on the dome brick. I'm afraid that you will get more damaging heat from the direct contact than you will from the flue gasses.
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Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build -
Thank you for your honesty. I'm not going to proceed with the wrong material in place. There is too much sweat and money in this for me to cross my fingers and hope for the best. Tomorrow I will remove the concrete, while cursing and throwing large chunks of mistake across the yard.Originally posted by Gulf View PostComment
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Personally, if I wanted to form it, I would get Ciment Fondu. You can probably order it from a cement supplier but the pain of it is you are also supposed to reinforce it with stainless steel needles (not rebar). Otherwise I would use firebrick.
I thought you had insulation under flue material and it wasn't sitting right on the dome - am I mistaken?Comment
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I only insulated the inside of the flue. Not the walls. Stupidly, I thought the 6"-8" of concrete would be fine directly on the back of the firebrick. I was thinking in terms of insulation and that it might not be the best option for insulation, but i would make that sacrifice due to ease and availability. I wasn't really considering that general purpose concrete wouldn't be able to handle the heat. I would have run the insulation under the walls but it didn't seem like it would be a good idea, since i needed it to support the chimney. I'm disappointed that I didn't wait to hear back from you all. I was ready to go and I made an impulsive decision.Originally posted by deejayoh View PostComment
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Hang on, I would like to hear what DavidS thinks about it. Since he has replied on this thread, he should be subsribed. There are a couple more, whose opinions that I would be interested to hear, that are probably not subscribed. I'm going to send them a pm. I hope that is ok.
Joe Watson " A year from now, you will wish that you had started today" My Build Album / My BuildComment
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Please do. Thank you for taking the time to work this out with me. I appreciate the help.Originally posted by Gulf View PostComment
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I was just reading this this morning. http://www.traditionaloven.com/tutorials/concrete.html Does anyone have any thoughts this recipe? I have access to all of the ingredients and thought that i might give it a try instead of shipping two 80lb bags of Ciment Fondu across the country.Comment
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I guess i would only need one bag but I can't even find a place that sells it.
I know that I could just build this flue section with fire brick, but i'm skeptical about its strength since i'm building it on a rounded dome. It will be supporting the weight of the chimney.
Another option would be to notch out a flat shelf along the backs of the oven fire bricks and build on that. But would that compromise the strength of the oven dome?Comment
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Not sure how close this place is to you but in Maine but they carry refractory cement. http://www.infabrefractories.com/
I know that David S. knows a lot more about castable/modeable refractory cement and stainless steel needles for strength. Check with him.Russell
Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]Comment
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I'm embarrassed that you found that and I didn't. It's only about 45 minutes away. I'll give them a call. Thank you very much! Should I try and contact David S.? I still have never tried contacting individuals on here. I'm sure that I can figure out.Originally posted by UtahBeehiver View PostComment
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Just send a Private Message under David S. He is in Aussie country so his time zones are different.Russell
Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]Comment
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Sorry that I am coming late to the thread. That is also the way that Italian ovens are built, though they do the entryway itself very different.
The loss of heat when you are not actively firing far outweighs any benefit you get from flue gases heating the back side of the brick (plus it would create a hotspot in the ceiling, which is also not desirable). You should insulate between the oven and the flue chamber.
Perl-crete at 5 or 6 to 1 should be fine for the insulation and creating the flue chamber, but it should be parged with a heat resistant mortar on the inside and regular mortar on the outside. It has more than enough compressive strength to support a full masonry chimney.Comment
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No problem for being late. I appreciate your input. I cut out the general purpose concrete and was able to salvage the forms I had already used. I re-leveled them and poured noxcrete (a concrete made for high temps) that I found at a nearby vendor. I used the 8lb 1" insulation on the inside of the flue on top of the dome (back of firebrick). I am going to spread a thin layer of fire mortar over it and then line it with stainless steel sheet metal so the insulation will never see a flame or spark.Originally posted by Tscarborough View PostComment
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Not pretty, but will work. I was able to get away with using 100 sq feet of 1" insulation. It is 4" thick around the oven. I will probably lay some on top of the metal to insulate the exterior clay brick dome from the high heat in the flue. I also have set the pin on the top of the oven so I can use this bent metal as a guide for the outer dome.
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