kkp
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Post by kkp on Apr 26, 2018 18:23:53 GMT -8
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Post by gadget on Apr 28, 2018 16:01:16 GMT -8
I have never used castables before but that mix you listed should already have a binder included. Added portland would go against the recipe and would not be necessary and make it weak. Portland breaks down completely inside stoves hot environments. There are refractory mixes that use calcium aluminate cements as the binder but it is only there to hold it together till it is strengthened after firing(curing).
There is lots of conflicting info on portland heat degradation. Problem is there are allot of factors. Two main problems are you are basically turning the cement back to clinker or calcining it back to its pre wetted state...basically dehydrating it by breaking the chemical bond with water and also the thermal cycling degradation. Basically, portland can't handle heat. Even low temps have a long term creep affect on portland.
red brick is more heat resistant then portland but I would not use it in the flame path. I believe its down fall is it can't handle heat cycling very well, it tends to crumble easily.
Do you have any drawings of your setup?
-Gadget
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kkp
Junior Member
Posts: 55
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Post by kkp on May 4, 2018 11:38:38 GMT -8
No drawings. I was just looking for a way to reduce costs. I think I can get by with maybe three 50lb bags of refractory cement. I was laying out the basic footprint this morning. The core will be inside the bell, with the riser being at the exact center of the bell. I'll make the top of the bell out of the castable. I'm thinking two slabs 44" x 22" x 2" to reduce heat cracking. The outside dimensions of the bell are 44" x 44". I'm not real concerned about instant heat from a metal surface. Pretty sure a 1/8" x 44" x 44" piece of plate steel would cost about the same as the refractory cement and I'm not sure 1/8" would be thick enough. Here's an image of the footprint I layed out this morning. s18.postimg.cc/v9mslczjd/20180504_115050_a.jpgIn the background is the existing chimney I'll be using to exhaust flue gasses. There's a clean out at floor level that I plan on using. What I will probably do is extend the clean out with some bricks and use those to connect the bell rather than using metal pipe. Perhaps I can use regular cement down there as I expect temps to be pretty low at that point. The core will be all ceramic fiber with the red clay brick shell. First to go down inside the core area will be a sheet of durock and then I will build the core on top of that out of ceramic fiber boards. The reason for the cement board base is just in case I decide to sell the house, that way I can move the core without disassembling it. Not likely to be selling but you never know. So far keithturtle has not gotten back to me so I may have to use the ceramic fiber blanket I bought to build the riser. I'd rather have a solid vacuum formed riser but if he hasn't responded by the time I'm ready to install that part I'll have to go with the blanket. Heading over to see about buying the castable now. Hoping it's under $70 a bag. |
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Post by gadget on May 5, 2018 19:46:19 GMT -8
I wish I had an exact number for safe working temps of portland. I have an area at the end of my heater I would like to use it. I may just go ahead anyway and if it starts to break down then I will just remove it. I am also trying to reduce cost where ever I can. I already have over $500 in materials so far. My goal is to stay under $2000
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Deleted
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Post by Deleted on May 6, 2018 5:12:14 GMT -8
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Post by gadget on May 8, 2018 20:55:16 GMT -8
I gave it a quick look over but will have to wait for some free time to read it. Anyone brave enough to try and extract some useful info that relates to uses in wood burning appliances? |
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Post by ronyon on May 9, 2018 4:03:34 GMT -8
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Deleted
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Post by Deleted on May 9, 2018 5:26:17 GMT -8
ronyon there is a reason why the the company does not officially give it a high service temperature. The SDS of Cement All says decomposition temperature 2460 °F (1350 °C). www.ctscement.com/wp-content/uploads/2014/02/SDS_Cement-All_2014_1007_1.pdfA given decomposition temperature does however not imply by any means that it actually could withstand temperatures up to this boundary.The SDS also says Silica Sand, quartz 40-60%. From the paper which I have linked: Many common coarse aggregates are unsuitable for high-
temperature service because they contain quartz,
which exhibits a large volume change at ~575°C.
With fine aggregates the effect is less pronounced, but nevertheless destructive. The H.C. Muddox Fire Clay could likely replace the kaolin in DIY Geopolymer - code named Kansas City #1 donkey32.proboards.com/thread/3283/geopolymer-code-named-kansas-cityThe upper limit for cement in the recipe is about 20%. With higher amounts of cements the temperature resistance will be lowered to about 900°C, which however would be sufficient in many areas of a stove. White cement works better than gray cement.
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Post by gadget on May 9, 2018 17:40:01 GMT -8
It is Calcium Sulfoaluminate Cement, never heard of it before. It sounds like the sulfur content is a sort of flux for making the clicker at a lower temperature?  I'm not sure how much it differs from calcium aluminate cement. I know the former is used as a binder in some refractory mixes. That home depot cement looks promising but the sulfur content would be of concern for stove parts down stream or possible nasty gases out the flue? -Gadget |
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Deleted
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Post by Deleted on May 10, 2018 6:45:16 GMT -8
The name Cement All is misleading as it is not a cement but a mortar.
The sufur cointent is of concern, but not due to nasty gases.
The decomposition temperature of 2460 °F (1350 °C) will hardly be reached in a wood burning device.
Ettringite, a hydrous calcium aluminium sulfate mineral, is the curse of Portland Cement, partly due to its extremely high water content.
Without the gypsum milled with the Portland Cement clinker the refractoriness of Portland Cement would be on par with a low alumina calcium aluminate cement.
Calcium sulfoaluminate cement creates much more ettringite during hydration than Portland Cement.
Cynical mode on.
The gypsum could be easily replaced by another setting agent and thus Portland Cement
could be become able to withstand millenias just like Roman Cement.
However for the cement industry the weakness of Portland Cement is like an eternal licence to print money.
Cynical mode off
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Post by gadget on May 10, 2018 10:35:31 GMT -8
The name Cement All is misleading as it is not a cement but a mortar. The sufur cointent is of concern, but not due to nasty gases. The decomposition temperature of 2460 °F (1350 °C) will hardly be reached in a wood burning device. Ettringite, a hydrous calcium aluminium sulfate mineral, is the curse of Portland Cement, partly due to its extremely high water content. Without the gypsum milled with the Portland Cement clinker the refractoriness of Portland Cement would be on par with a low alumina calcium aluminate cement. Calcium sulfoaluminate cement creates much more ettringite during hydration than Portland Cement. Cynical mode on.The gypsum could be easily replaced by another setting agent and thus Portland Cement could be become able to withstand millenias just like Roman Cement. However for the cement industry the weakness of Portland Cement is like an eternal licence to print money. Cynical mode off
This just became a more interesting topic due to the potential. I was reading that this mix is popular in China due to the lower clincker forming temp = less energy to produce. I am very interested in it, especially with the availability in big box stores. Home depot online say 103 in stock at my location. The big question I have though is, why is this not a common refractory binder? Is this a new product??? |
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Post by Deleted on May 10, 2018 14:20:16 GMT -8
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Post by gadget on May 10, 2018 19:53:50 GMT -8
Nope, no joke at all. I was just wondering why I have never heard of CSA used as a refractory binder before. I have seen many references to CAC but never CSA and was wondering why that is. I would love to see a commercial recipe that uses it just to know there are no issues with the sulfur component. |
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Deleted
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Post by Deleted on May 11, 2018 6:38:53 GMT -8
gadget I have precisely explained why it is unsuitable for refractories. Therefore I was wondering if you had tried to make a joke.
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Post by gadget on May 11, 2018 8:11:03 GMT -8
gadget I have precisely explained why it is unsuitable for refractories. Therefore I was wondering if you had tried to make a joke. Ooh I missed that. Apparently I need to read it 3 times to get that point. Ettringite = easy dehydration(?). For some reason I had it back wards in my mind. To many sleepless nights lately with kids being sick my mind is like oatmeal lately. Thanks karl! Would of been nice if it was good for refractory use. -Gadget |
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I'm not sure how much it differs from calcium aluminate cement. I know the former is used as a binder in some refractory mixes. That home depot cement looks promising but the sulfur content would be of concern for stove parts down stream or possible nasty gases out the flue?