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Post by sksshel on Jan 30, 2018 6:33:37 GMT -8
Updated Procedure: - Mix the monopotassium phosphate and Soda ash powders - Add boiling water This causes a reaction to drive the carbon out. Look for No new bubbles on the surface, no fizzing sound, no volume increase. This should conclude within a few minutes. - Add the citric acid. Wait until the reaction comes to a halt. This should conclude within a few minutes. - Add Rockwool, Portland Cement and Clay - Let the end product cure until hard. 27°C/80°F are only slightly above ambient temperatures (20-25°C). Curing time with some caustic lime or cement should be less than a week. The measuring of the materials takes the most time by far. This truly is an easy process. |
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Post by pigbuttons on Jan 31, 2018 16:50:39 GMT -8
You guys rock (pun intended). Great thread and thanks to all for the information sharing.
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Post by sksshel on Feb 1, 2018 15:44:33 GMT -8
Will this product further cure during initial firing of the stove?
In other words, should I use a gradual process of firing? I've seen comments along those lines in other threads.
Another question, when this product is completely cured, will it be water resistant?
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Deleted
Deleted Member
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Post by Deleted on Feb 2, 2018 7:27:01 GMT -8
In any castable refractory the not fully refractory bonds will be replaced by ceramic bonds in the initial firing.
The heat may also change the structure of the material.
Manufacturers request a gradual process of firing to keep the heat stresses low
and to ensure that the ceramic bonds can be established before the destruction of the prior bonds.
Yes, it should become water resistant.
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Post by sksshel on Feb 3, 2018 9:14:55 GMT -8
A couple observations after almost 2 weeks of curing:
- nearly 10% shrinkage so far (should I expect more)
- due to shrinkage the formula requires 4.2 times to make a liter
In order to build the pieces to the exact measurements required for a Batch Box Rocket Mass Heater, I will need to make the forms larger than required. I can then cut the pieces to the final required dimensions.
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Post by sksshel on Feb 3, 2018 15:42:03 GMT -8
I saw a post on another thread by Karl. It mentioned 20% fiber in response to the shrinkage problem. This would be sample #5.
monopotassium phosphate 29g 7%
Soda ash 26g 6%
Water 4oz 1%
citric acid 3oz 1%
portland cement 59g 15%
clay 200g 50%
fiber 80g 20%
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Post by pigbuttons on Feb 6, 2018 6:58:05 GMT -8
I saw a post on another thread by Karl. It mentioned 20% fiber in response to the shrinkage problem. This would be sample #5. monopotassium phosphate 29g 7% Soda ash 26g 6% Water 4oz 1% citric acid 3oz 1% portland cement 59g 15% clay 200g 50% fiber 80g 20% Karl can correct me if I'm wrong, but I believe the fiber is to prevent cracks from forming during shrinkage, not so much to prevent shrinkage. But I'm very interested in what you are doing here so please keep us up to date with your progress. |
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Post by sksshel on Feb 6, 2018 9:00:37 GMT -8
Sample #5 is mixed. Observations:
- Much more time spent on prepping the fibers than the rest of the process combined.
- Mixing of the fibers was more difficult. Next time I will mix in a little at a time rather than dumping it all together and then mix.
- The end product volume was significantly increased. It produced a little over 3/4 of a liter.
- I added 16 oz of additional water in order to facilitate mixing. I may be able to cut back on this a bit but not much. Possibly 2 - 4 oz less.
- The end product did not pour nor settle well when vibrated. I used a 2x6 to press the product into the form in order to hopefully get it packed down.
The product is now in the curing box. More updates to come.
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Post by sksshel on Feb 6, 2018 9:08:37 GMT -8
If sample #5 works out, the total costs for my project will be greatly reduced. I will need far less of all of the other materials. The Rockwool provides much-needed volume.
For 6 cubic feet of product, the total cost will be about $140. Shrinkage will drive that number up when it is determined.
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Post by coastalrocketeer on Feb 6, 2018 13:24:17 GMT -8
If sample #5 works out, the total costs for my project will be greatly reduced. I will need far less of all of the other materials. The Rockwool provides much-needed volume. For 6 cubic feet of product, the total cost will be about $140. Shrinkage will drive that number up when it is determined. My mix with zeolite binder/bentonite clay has just this goal... Probably doubled volume of the high water content gravy consistency mix with the large amounts of Rockwool. Not sure it's water proof and thus an actual geopolymer, but for a "first try" to actually build a functioning core, it should meet my needs well. A 1300 CC puck weighs 883 grams, and at 3.5 cm thick it never went over 200F on the backside through an hour of being torched continuously in the center of the frontside. |
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Post by pigbuttons on Feb 6, 2018 22:03:03 GMT -8
Sample #5 is mixed. Observations: - Much more time spent on prepping the fibers than the rest of the process combined. - Mixing of the fibers was more difficult. Next time I will mix in a little at a time rather than dumping it all together and then mix. - The end product volume was significantly increased. It produced a little over 3/4 of a liter. - I added 16 oz of additional water in order to facilitate mixing. I may be able to cut back on this a bit but not much. Possibly 2 - 4 oz less. - The end product did not pour nor settle well when vibrated. I used a 2x6 to press the product into the form in order to hopefully get it packed down. The product is now in the curing box. More updates to come. It seems slightly counter intuitive, but when lighter ingredients are added vibration no longer works. My thoughts on this is that the vibration cannot travel through the lower density material and therefore the vibration wave cannot move through the mass as well. It will however still drive out trapped air but it may also introduce voids. Tamping or pressing is more appropriate for light weight mixes than vibration in my opinion. Mixing of the fibers was more difficult. Next time I will mix in a little at a time rather than dumping it all together and then mix.
Another technique to try is mix up everything else and then pour about 1/4 of that mix into another vessel and add 1/4 of the fiber, repeat until the entire batch has been transferred and blended. I don't recall how you purchased your rockwool but if you look for the "blown in" variety it will already be in small clumps that can then be further processed more easily if needed. |
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Post by coastalrocketeer on Feb 6, 2018 22:22:55 GMT -8
I got big 4" long by 15" wide 3.5" thick batts. I initially cut it up, but then realized with a later batch that if I used the red paint stirrer, I could just tear int strips and achieve shorter fibers by mixing longer... The other one might work in a 10 or 15 gallon vat, but splashed too much of my liquid mix upward in a 5 gallon bucket.  Tamping and applying to my mold like paper mache was how I did it. To achieve the right consistency, Added fiber to the bucket in 2" thick layers of chunks then dumped a suitable amount of mix on, then another layer of fiber and repeated til the bucket was half full. Alternated between shoving loose fibers from the top downward with the drill off, and working the mixer horizontally through the mix's different layers, occasionally letting it spin it's way around the edge and throw material back to the middle. Kept adding fiber until the overall mix was fully saturated, and a squeezed handful did not fall apart...  All of this was with a very liquid mix... |
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Post by sksshel on Feb 7, 2018 3:42:29 GMT -8
I don't recall how you purchased your rockwool but if you look for the "blown in" variety it will already be in small clumps that can then be further processed more easily if needed. Thanks for your input. I will try your suggestions. I already had the rock wool on hand for another project. It is the "Batt" type. I will need upwards of 40 lbs of it for my project. The blender method is not going to cut it. I am thinking about using a weedeater with a brush cutting blade. Doing that much by hand can be done, it is just not desirable. |
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Post by coastalrocketeer on Feb 7, 2018 18:48:51 GMT -8
If I had been able to find it easily I would have gone with the loose fill/blow in format, but as it worked out I was having to shop for it while visiting family in a metro area so was limited to big box home stores due to being there on the weekend. All they had was batts. The one thing I forgot to mention... Instead of tearing, when doing bulk quantity breakdown of the batts, was that I used a pair of Fiskars garden shears like scissors and cut across the batts the short way, approximately 1" wide strips... Takes about three "snips" to go all the way across the batts...   When doing the last batt and a half I did this way, I layed the batt standing vertically, between my knees and ankles and made my cuts down toward the ground, out in front of me... Those 1" strips are easily hand torn after that if further breakdown is necessary, but the mixer was enough with be viscosity of mix I was using.  Breaks apart easily after that with the mixer, and no huge clouds of fibers is produced, as I would expect breaking the batts down with any high speed blade would produce. |
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Post by sksshel on Feb 13, 2018 6:46:06 GMT -8
The sample cuts easily with a hand saw.  |
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