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Post by Deleted on May 12, 2018 8:10:47 GMT -8
One may be able to get away with small amounts of pure CSA cement as the binder.
The paper which I have linked provides all information required to design a refractory mixture.
Unfortunately it may be a problem in the USA to get the required components at a reasonable price.
You are lucky if you have a shop of Axner, Clay-Planet, Portland Pottery or TheCeramicShop near you.
BTW Rutland sells Castable Refractory based on Portland cement as the binder rated for 2200°F/1204°C.
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kkp
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Post by kkp on May 12, 2018 9:22:36 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 $2000Yeah, way under in fact. I'm at about 750 which includes all the ceramic fiber I need + 3 bags of castable refractory and 100 red clay bricks. I just need more bricks and the mats to make mortar.
My dogs stay in the basement while I'm at work so I'll need to water proof the bottom foot or so of the bell. I can't go more than about 4 hrs without peeing, I can't expect them to either. Anyone who says different doesn't care about the health of their pets. I really like my dogs and with careful control of what chemicals they come into contact with and species appropriate food I expect 25 healthy years of life for them
There is a guy in Australia who just recently lost his dog to extreme old age, she was a kelpy and died at 30 yrs old. Similarly, a man in Texas holds the Guinness world record for the oldest cat at 38 yrs old. So, I know 25 years is do-able for Pedro and Stryker |
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Post by Deleted on May 13, 2018 9:11:44 GMT -8
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kkp
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Post by kkp on May 13, 2018 9:37:46 GMT -8
So, fireclay + portland cement is a decent refractory?
Let me re-define my original question.
The use intended for this specific application would NOT be in the core but rather in the masonry bell area. I'm pretty sure temps would never be above 500F. In fact if my bell ever reached a temp of 500F I would be seriously considering calling the fire dept.
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Post by Deleted on May 13, 2018 10:04:38 GMT -8
Yes, it is possible to use Portland cement to make a decent refractory up to 2200°F/1200°C. It is very simple to make Portland to resist up to about 1650°F/900°C. One needs about 20% pozzolan and some lye. Fine grog is better than fire clay, but fire clay is sufficient. White portland is better than the grey. The best result I have got with monopotassium phosphate which was reacted with lye. Monopotassium phosphate 10%, lye 5%, fire clay 20%, Portland cement 65%. Avoid quartz sand like the plague, use grog or slag sand instead. Keep the aggregate to binder ratio low.
Higher amounts of fire clay are possible.
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kkp
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Post by kkp on May 13, 2018 10:55:44 GMT -8
Yes, it is possible to use Portland cement to make a decent refractory up to 2200°F/1200°C. It is very simple to make Portland to resist up to about 1650°F/900°C. One needs about 20% pozzolan and some lye. Fine grog is better than fire clay, but fire clay is sufficient. White portland is better than the grey. The best result I have got with monopotassium phosphate which was reacted with lye. Monopotassium phosphate 10%, lye 5%, fire clay 20%, Portland cement 65%. Avoid quartz sand like the plague, use grog or slag sand instead. Keep the aggregate to binder ratio low.
Higher amounts of fire clay are possible.
Considering: Monopotassium phosphate 10%, lye 5%, fire clay 20%, Portland cement 65%
At 8-10 dollars US that would be $80 - $100 just for that ingredient. I can get premixed 2300F refractory for $126 for 110lbs.
Again, I'm not looking for a high temp refractory, What I am looking for is a cheap castable solution for the top of my masonry bell (36" x 36")
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kkp
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Post by kkp on May 13, 2018 12:00:31 GMT -8
Over at permies.com they are adding perlite to premix refractory mix to make it go farther. Maybe that's my solution considering I already have 3 bags of premixed refractory
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Post by Deleted on May 13, 2018 12:45:33 GMT -8
The Kansas City geopolymer thread of sksshel gives a much cheaper source for monopotassium phosphate. You may also look at agriculture shops. A LTGS binder made from lye and clay works as well. Those perlite mixtures are just loughable. |
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Post by gadget on May 14, 2018 1:17:09 GMT -8
Over at permies.com they are adding perlite to premix refractory mix to make it go farther. Maybe that's my solution considering I already have 3 bags of premixed refractory Perlite is a great insulator which you probably don't want in your bell. It also makes things weak. It is horrible as a grog. It can be used in the outer portion of insulated burning areas. You are working on the bell for your build. The top of the bell has to be the hardest part of the design. Think about it; 1 It has to be refractory 2 cover a wide span 3 hold up weight 4 handle heat cycling 5 ?.... I think if you could come up with a good cast lid then its just bricks from there right? Is that what you are planning? I think this is why rockets with the steel barrel setup are so popular, it is a simple and cheap solution. I'm thinking of going the non exposed steel bell route. I would love to just make a bell out of steel and cover it with cob. Still researching that idea. I have concern with possible moisture buildup though due to a new design change that would be lower internal temps and causing rust through. I have a large sheet of 3/16" steel plate I would weld up and use instead of a barrel for longer life. Cheap, Strong and Last forever... Pick two |
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Post by branja on May 17, 2018 1:14:35 GMT -8
Yes, it is possible to use Portland cement to make a decent refractory up to 2200°F/1200°C. It is very simple to make Portland to resist up to about 1650°F/900°C. One needs about 20% pozzolan and some lye. Fine grog is better than fire clay, but fire clay is sufficient. White portland is better than the grey. The best result I have got with monopotassium phosphate which was reacted with lye. Monopotassium phosphate 10%, lye 5%, fire clay 20%, Portland cement 65%. Avoid quartz sand like the plague, use grog or slag sand instead. Keep the aggregate to binder ratio low.
Higher amounts of fire clay are possible.
Can you explain(for a layman) a bit abouth the ratio of that much portland + more Ca + more alkali.? Isnot that just onesided alkali+ high Ph ? Or the "good reaction" is the phosphate coordination+ metal oxides in fire clay? Or (please forgive the oversimplification) fire clay gives "decent al/si ratio" to make "-ions" and alkali gives the "+ kations". Im not a chemist to see why that much portland? |
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Post by Deleted on May 17, 2018 5:09:05 GMT -8
Why that much portland?
Just to make it as cheap as possible.
More than about 20% portland cement reduces the heat resistance to about 900°C.
65% do not make it worse, but cheaper.
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Post by sksshel on May 18, 2018 11:29:14 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 I am using a geopolymer recipe that I got much help from @karl developing. I am constructing the Batch Box core, Shoe Box core, Heat riser and Lining the Bell with it. I've cast the parts and cut the product to the precise dimensions. All of my geopolymer components cost less the $300. If you add in the cement blocks and the metal components you are looking at less than $600. I have not yet purchased the glass for the 2 doors yet so that will be on top of that. These numbers do not include the chimney through the roof. The geopolymer should easily handle over 3000 oF. |
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Post by gadget on May 18, 2018 21:46:50 GMT -8
Hey karl and sksshel,
This sounds very interesting, especially on the low cost. My stove design has changed such that this could be useful. I'm interested in some material that could handle moisture that may linger around the floor or other areas of a vertical double bell.
Any thoughts on how well the geopolymer you are using would hold up as a hot face, say inside a firebox covering ceramic fiber board? Say 1/8" - 1/4" thick? Any info on expansion rate / heat cycling toughness?? I'm guessing this cement is a permanent phosphate bonded?
I'm going to have to dig through some threads and find a recipe to experiment.
-gadget
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Post by sksshel on May 19, 2018 4:19:27 GMT -8
Hey karl and sksshel, This sounds very interesting, especially on the low cost. My stove design has changed such that this could be useful. I'm interested in some material that could handle moisture that may linger around the floor or other areas of a vertical double bell. Any thoughts on how well the geopolymer you are using would hold up as a hot face, say inside a firebox covering ceramic fiber board? Say 1/8" - 1/4" thick? Any info on expansion rate / heat cycling toughness?? I'm guessing this cement is a permanent phosphate bonded? I'm going to have to dig through some threads and find a recipe to experiment. -gadget I recommend you read the thread on Kansas City #1. Let me know if you have questions after reading it. |
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Post by Deleted on May 19, 2018 6:34:42 GMT -8
gadget the simplest geopolymer recipe is 10% lye, 10% quicklime and 80% fine grog, mixed to the consistency of evaporated milk and then filled with aggregate. At some shops you may be able to get grog for less than 50 cent per lib if you buy 100 lbs or more. Scoria has a low thermal expansion and conductivity. Lava sand is available for a few dollar per cubic foot and less than $100 per tonn. The cheapest geopolymer is a LTGS mixture with a binder made from 50% lye and 50% clay.
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