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Post by Jura on Dec 12, 2018 0:10:58 GMT -8
First am going to figure out a way to accurately measure volume so I can compute grams/cc dry sample weight. having committed a few stupid errors in volume calculation I found out the least erroneous way is to draw an object in sketchup then check its volume in the object properties panel |
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Post by coastalrocketeer on Dec 12, 2018 0:44:34 GMT -8
That would work if my castings were perfect, but some had irregular thickness from being “springy” mixes difficult to trowl flat, and those where edges or corners broke off from early demolding, or where the amount I made filled the mold box some amount less than full.
I wound up filling a plastic sour cream bucket with table sugar, scraping the top off flat, and pouring that amount of sugar off into a tub. Then measuring how much 100ml of table sugar weighed (90.6666666 grams in my case)
I placed the blocks in the tub and then filled it, scraped the top flat, and weighed the sugar displaced. Divided by .90666666 to get the number of ml/cc of sugar displaced.
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Post by coastalrocketeer on Dec 12, 2018 12:01:38 GMT -8
I am trying to work out both insulative and structural mixes. I basically collected materials and dissolution agents (acids and alkalines) based on Karl’s threads here, with some of them being substitutions, based on what was available to me (semi-) locally.
I am initially building a batch rocket for me, and hopefully developing some refractory mixes that will allow me to cast outdoor rocket cookstove burners, and my own batch rocket home heater as testbeds for the mixes... to ultimately cast shippable batch box and j tube rocket stove cores as a profit making enterprise...
The mix development I intend to keep open source, as that is the way I am learning here, and I want everyone who wants to, to be able to benefit from anything I develop from all the info Karl and others have freely shared for the benefit of all here.
I’m in a tiny town on the Oregon coast... some materials required 2-4 hour round trips, as getting to the metro areas is a 3 hour round trip minimum.
The only things I obtained without the long travel times were citric acid, which I found for $15 for 5lb bags & 2lbs of KOH 92% flakes from eBay, white 5% table vinegar from the grocery store, SweetPDZ stall freshener (clinoptilolite zeolite) and sodium Bentonite clumping cat litter came from two local farm and feed stores in the next two towns north of me.
The two Kaolins, EPK and McNamee, as well as Lincoln 60 fireclay, Custer feldspar, and nepheline syenite A270, came from Georgie’s ceramic and Clay, in Eugene and Portland. (Eugene didn’t have the McNamee in stock, so had to make a second 6 hr trip to Portland for that)
The red cinder track sand is crushed volcanic scoria and was obtained on a separate 4 hour round trip to Eugene from a landscape supplier, Lane Forest Products, and likely comes from central Oregon, east of Lane county. On that same trip I also picked up the coal slag sand blasting abrasive from Tractor Supply, yet another farm and feed chain store with the nearest location to me being south of Eugene
Rockwool batt insulation, and Type S hydrated masons lime, and NaOH came from Big box home centers on other trips to the valley.
It has taken me a while to get the collection of materials I did, with the intent of having an array of binder feedstocks, attack agents, and aggregates available to experiment with, and life has kept me, as well, busy with other more pressing and immediate needs.
Hopefully I will come up with some decent refractories that all can benefit from. Experimenting so far with adobe consistency and ram mass consistency mixes, but hoping to experiment with layered build up on molds and other methods for more liquid mixes that Karl has suggested.
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Post by Jura on Dec 13, 2018 6:08:24 GMT -8
Hopefully I will come up with some decent refractories that all can benefit from. Experimenting so far with adobe consistency and ram mass consistency mixes, but hoping to experiment with layered build up on molds and other methods for more liquid mixes that Karl has suggested. Thanks for your answer and open source. I compared prices of a few of ingredients and I must say we are pretty lucky here in Upper Silesia with regards to prices (and less as to air pollution). Most of GP's are pretty heat resistant up to 900 deg C. Have you manged to obtain any mold that withstood higher temp ranges, yet? I'm still finding time only to plod through Davidovitz's "Geopolymer Chemistry and Applications" book. |
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Post by Deleted on Dec 13, 2018 8:07:19 GMT -8
Most of GP's are pretty heat resistant up to 900 deg C. Up to 900 deg C is for mixtures with portland cement content significantly above 20%. For mixtures without or only with smaller amounts of portland cement the resistance is a lot higher, more than sufficient for wood stoves.
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Post by coastalrocketeer on Dec 13, 2018 11:10:16 GMT -8
These are the samples I torch tested last night... None had spalling issues, and only one (the desnsest) had any structural failure.  They were each subjected to 10 minutes of heat concentrated in a single spot on one side, from a BernzOMatic TS4000 propane torch. I did actually make a working core out of a mix that I made of zeolite, Bentonite, and high quantities of Rockwool. Was a T shaped feed and burn tunnel section made of that mix, with a ceramic fiber “5-minute riser.  It was not a particularly strong mix as I was going for lightweight and high volume with a minimum of materials. It turned out not to be waterproof (except where it was fired by the heat of about 10-15 hours of operation, and was destroyed by a particularly windy rainstorm blowing the cover I had over it off a couple of moths ago now. I used it to carbonize bread foam and test fire a couple of geopolymer blocks I made with my daughter’s air dry sculpting clay, over the riser. After the rain storm it was back to adobe consistency, except in the inner areas that actually got hot enough to “fire” it effectively. As a testament to it’s insulative value, over 10-15 hours of combustion, that “fired area” was only 1/4-1/2” deep. The material seemed to reflect the fire’s heat back in and got extremely hot, to where, at the height of a fire, adding a stick of wood, it would blacken and begin surface combusting in a few seconds...    The structural issues were due to my poor technique at construction and not really having come up with a proper “geopolymer mix”, before blustering ahead with that one. During multi hour burns, the exterior of the core never got over about 400F (it was cooled externally by exposure to 60F moist coastal air) |
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Post by Jura on Dec 13, 2018 14:25:54 GMT -8
Up to 900 deg C is for mixtures with portland cement content significantly above 20%. For mixtures without or only with smaller amounts of portland cement the resistance is a lot higher, more than sufficient for wood stoves. Thanks! I had this # of 900C in my mind from a presentation of profesor Janusz Mikuła: (all in polish lng, but the 900 oC is mentioned at the 8th page of the below linked is presentation) odpady.nfosigw.gov.pl/gfx/ees/userfiles/files/67_forum/3.67.pdf (page 8) But after your info I checked geopolimer wbesite and found this art : "Geopolymers with the Potential for Use as Refractory Castables"www.azom.com/article.aspx?ArticleID=3171 |
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Post by smartliketruck on Dec 13, 2018 16:29:26 GMT -8
These are the samples I torch tested last night... None had spalling issues, and only one (the desnsest) had any structural failure.
It's very cool of you to spend so much of your time and money to investigate such a wide variety of materials 
Here's a couple of things I've learned that may help others going the same route.
When I torch test samples I stick around as it cools so that I can listen to the tiles cool, you can distinctly hear the tink tink tink sound of internal heat stress fractures.
A cheap little electronic jewelers scale from amazon, ebay or a paraphernalia shop will quickly pay for itself in reduction of wasted materials for "I wonder if..." trials.
A inexpensive mains voltage electronic temperature controller from amazon or ebay controlling a second hand shop toaster oven will save on using the big oven in the kitchen and stress to your significant other of always having little containers of mud cooking in their oven 
While at the second hand shop also watch for straight sided inox/stainless steel mixing bowls, it makes a big difference for spillage while trying to mix a liquid with a semi-solid, a electric hand mixer with dough hooks can also be a really big help.
Looking forward to seeing what you come up with here coastal!
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Post by coastalrocketeer on Dec 14, 2018 13:54:08 GMT -8
I am trying a mix with 60g zeolite binder, 25g NaOH, and 80g kaolin, 40g feldspar, 5g nepheline syenite, and 5g food grade diatomaceous earth, with a major portion of Rockwool as a “structural filler that allows fast drying” I did a test mix and it made a 13x23cm by ~1cm slab. Made it like a thin slip/gravy by adding a lot of water to the mix, then added shredded Rockwool until little mix “drained” to the bottom of my tub when I pushed the mass of it to one side. Packed it in like adobe, forming it with two kitchen forks to a roughly rectangular shape of roughly uniform thickness. Placed it in the 180F oven to dry/cure overnight with the top open, sitting on a layer of plastic “oven baking bag” to protect the steel pan from caustic attack. It cured & dried quite hard by morning. Calculating the volume is tricky due to the less than uniform hand forming, but i’m guessing but it weighs around 1.0 to 1.2g/cc somewhere around 30-40% Rockwool by weight, i’d guess. Haven’t done the math, just added it by “feel” based on the workability and solution retention of the Rockwool.  Top view^^^  Bottom view^^^ |
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Post by coastalrocketeer on Dec 14, 2018 13:57:31 GMT -8
 Close up of bottom side ^^^ The solution migrated to the drying surfaces and soaked away from the plastic (down) side, giving a hard brown skin on all the edges and top surface exposed to dehydrating air. The edges where solution tapered out onto the plastic were very hard to break off, and sharp, almost glass like. I would guess from the first couple of hours of monitoring, it took 6-10 hours to dry completely. There are no signs of any drying cracks even though the mix was probably multiple times H2O weight to dry ingredient weight. part of this unusually high water ratio obviously being attributable to high volume to weight of the Rockwool, and the associated support for more rapid drying. |
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Post by coastalrocketeer on Dec 14, 2018 14:18:36 GMT -8
So I put together a jtube mold out of old half and half cartons, super glue, and baking soda (makes super glue cure crazy fast) Am making 4X as much more binder/clay mix and hoping to get enough Rockwool chopped up to put an initial 1cm thick layer over the mold and get it into the oven to cure/dry overnight.  |
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Post by coastalrocketeer on Dec 14, 2018 14:27:17 GMT -8
Here is a closeup of the “dehydration” side...  The prtected side is sofrer and a knife blade can be pushed into it, like a harder ceramic fiber board. The skin on the “drying side” is hard and I can’t easily push a knife blade through it. |
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Post by smartliketruck on Dec 14, 2018 15:07:19 GMT -8
Are you adding the nepheline syenite and feldspar to vary the particle size within the mixture?
If I recall correctly, Karl was suggesting them for organic acid activated binders due to having alkali metals already in them.
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Post by coastalrocketeer on Dec 14, 2018 16:13:46 GMT -8
smartliketruck Avatar
Dec 14, 2018 15:07:19 GMT -8 smartliketruck said:
Are you adding the nepheline syenite and feldspar to vary the particle size within the mixture?
If I recall correctly, Karl was suggesting them for organic acid activated binders due to having alkali metals already in them.
The feldspar as the predominant addition is because Karl suggested it as something that would support thinner mixes due to particle size... and the other two were just kind of “add a little bit because I have them,” with the DE being because somewhere I had seen it suggested that it could help initiate polymerization (if not dissolved) somehow.
I wish I understood the desired silico-aluminate balance better and was calculating my mixes to achieve outcomes within that range.
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Post by coastalrocketeer on Dec 15, 2018 0:58:12 GMT -8
Mold coated with mix...  At about 2-3/4” System size I am probably pushing the lower limits of what will work... presumably will be dry tomorrow, if the second batch of the mix hardens up as well as the first. It was a little wetter, but more Rockwool added until no liquid “dropped” out the bottom when I packed it against the side of the bucket. I will also get to see how well it handles “cold joints” in whether it attaches it’s self to the already dried base plate. |
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