SweetPDZ Zeolite geopolymer first try... Promising Jan 10, 2018 1:41:56 GMT -8 via Tapatalk serg247 likes this
Post by coastalrocketeer on Jan 10, 2018 1:41:56 GMT -8
Any curing of my one "burger patty" puck that came from the leftovers last time was done 100% during the torch firing, I would say. As I only dried it for 4 hours or so in the oven at 170F to 190F, then torched most of both sides for a number of minutes each.
It dried quickly and without any visible cracking, which would only be possible with this thin mix consistency and type of binder, and such a high swelling/water demand (bentonite) clay as aggregate, with a LARGE amount of mineral wool by proportion, to provide moisture removing and semi-structural substrate and crack prevention reinforcement.
It may behave totally differently and likely poorly without being used in this manner, where it is always in thin enough areas by it's self, with plenty of fibers, to not "alligator crack" as the bentonite shrinks (a LOT) as it dries, and thick spots of the mix on the surface in my failed "whole blanket saturation" portion of the last test, alligator cracked horribly while drying. There was not enough moisture in the mix and the blanket seemed to dry mix quickly at the surface with it's own water demand, and not allow full saturation. My saturation technique on that part failed, as I imagine if i had squeezed and manipulated the blanket more after coating both sides, or temporarily vaccum sealed it in a bag, then let it "re-expand" after being compressed and evenly saturated, my results with that might have been much improved, as proper integration of the GP mix into the mineral wool blanket seemed to be the main difference between my failed portion and my successful "bits of fluff, stirred into binder" side experiment, with the "table scraps"
The stuff may not be "cured" at all, after that short period of drying at mild heat, and might never actually cure to become water proof, or might require significant time at heat to actually cure and become truly water resistant.
I still need to water test some of the samples both torch-fired and un-fired, to see if it meets Karl's 24 hour immersion test standard, but for the immediate application in my build, it is not necessarily needing to be water resistant, or a true geopolymer. Just be a good refractory, pretty well air-tight and semi-structural enough to conduct gas flow, and support ceramic fiber blanket as a heat retaining backer, holding it's shape in the absence of physical abuse.
Based on the similarity of binder preparation to my "zeolite as aggregate AND binder mixes that DID pass the 24 hour water test, I suspect this might too, after sufficient time at higher temperatures through and through.
The material where I did not torch treat it, was weaker to begin with than the well torched part. This is at least partially due to the surface sintering/glassification. And possibly some sintering/curing throughout, though the surface glassification was definitely harder and stronger than the less heated parts even after torched thoroughly for a number of minutes and getting backside readings in excess of the 630F range of my IR temp gun.
Bear in mind we are dealing with a chosen mix and method, that did not come out much harder than the denser grade of "slag-wool"/fiberglass acoustical ceiling tiles I have worked with installing telecom cabling above them.
The ones that weigh somewhere between 5-10 lbs for a 24x48x1/2" thick panel. It is definitely not up to someone tossing large heavy pieces of wood into a fire box, even after glassification, and has weaker zones anywhere the mineral wool did not get sufficiently saturated with the "GP" mix, but definitely is self supporting enough to have wide ranging applications, but not suitable to replace firebrick in the "wood abused" areas of the stove, or to create any kind of slab of any significant structural requirements, at the current state of development.
My application and fuel type (bundles of twigs and small branches, will not require that type of "brick-hard" strength, but I imagine this material could make a great semi to non-structural, low to moderate insulative high heat resistance material of use in other stove embodiments.
For example, "line the top of your barrel inside with 1/2" or more to moderately reduce radiant heat output and make your barrel last 20 years instead of 10 before heat accelerated oxidation kills it. Or line the inside of the barrel wall anywhere you don't want as much radiant heat released in that direction. I imagine that type of application would take about $6-8 worth of ingredients (mineral wool, SweetPDZ, lye, bentonite) in order to line the top of a 55 gallon oil drum 1/2" thick, and about $20 to do the "wall side" half of your barrel with the current embodiment. Probably other more insulative but denser/heavier geopolymers could do this with less thickness of material, so this might not be the optimum product for that. It could be done in any thickness to all or any lesser portion of your barrel inside to change to more of your heat going into the thermal mass/bell(s) if you wanted to reduce radiant heat and increase mass storage. Could also have application in kilns and other designs I haven't even thought of, so it will be interesting to see how it performs as a stove wood feed and burn tunnel, and what other uses and method/material improvements I can come up with.
As this mix stands, it is not as insulative as LD CFB, but seems significantly stronger, especially where a thicker portion of GP mIx is saturating the surface, and more so, once glassified/sintered at the surface. Like the ceiling tile material I described, or a bit stronger, with a glassy/harder coating. My sample was not thick enough to really tell how much strength difference there was in the center portion that probably reached 800-1000F or so for some minutes. It was definitely interesting to see how different the two sides were in terms of that glassification (top, finger pressed and open to air during heated drying, and the bottom that was pressed down during forming, and dried slower, against the plastic.)
Interestingly, the glassification effect was more pronounced on the top side where most moisture left the mix during drying. May have migrated stronger lye concentrations to that side, and may have also had a stronger more contiguous layer of GP mix on the bottom side against the "oven baking bag" plastic that was protecting the aluminum pie pan from contact with the presumably caustic mix. (Makes my fingers feel "soapy", but causes me no irritation, but my skin has always had a good resistance to laundry bleach and other consumer strength caustic products...)
Perhaps because I eat a high (good)fat diet and have fairly oily skin, so plenty of fats in my finger skin to turn into soap before noticeable damage to tissue occurs. I have gotten pure lye grains stuck to my finger and dissolved by moisture in the air and been fine washing them off within 5 minutes or so. I know other people whose skin would peel off from such exposure.
Bear in mind my lack of need for gloves, besides my natural tolerance,
was with a 5% lye zeolite binder diluted with water in the final working mix more than would be "normal" for a lower water demand aggregate than bentonite, and when going for "ram-mass consistency", so probably less caustic concentration by volume than "brick" producing thicknesses of mix with other aggregates.
(On general binder mixing, also see my earlier comment to esbjorneer at the end of my latest responses to and additional materials and methods questions to Karl. He did not yet correct my process advice to E, so hopefully it was all sufficiently accurate and clear, and he did not just miss it because I addressed that section of my post to E.)
I have started my latest "test" that is actually going to be my first J-tube feed and riser section. I currently have had 2kg zeolite binder w/10% lye resting since mixing it last night. This afternoon I added 500ml more water and it is like a medium thickness gravy... Liquid but with significant viscosity.
Will be trying a little less clay aggregate in this mix, for a higher binder content and hopefully higher strength, but still enough clay to reduce/eliminate the bubbling at torch temps of my "all zeolite" (binder AND aggregate) geopolymers, that Karl said was an result of too much lye, though I used very close to the minimum amount he reccommended as required for all zeolite mixes...more than needed if used with other aggregates. So perhaps my lye is not reacting with enough minerals to "use it up"? I'm not trained enough to intuitively know the best methods for promoting chemical reaction and thus improving dissolution.
The mold I am using is OSB, so drying should happen some toward that direction and the majority through the exterior when I remove the plastic wrap I will use to press and shape it without it sticking to my gloves. Hopefully the inside face will act like the bottom (plasic bag) side of my GP rockwool "burger patty" and not bubble when exposed to heat.
Figuring on 1/2 hour to 1 hour working with this mix to shape the wet material around my core mold by hand, so going with nitrile hospital gloves to avoid exceeding my skin's tolerance for caustics and regretting it later...
Bear in mind that I am doing this in between other things so the long gap was for my convenience, and there may be no advantage to stretching out the "rest for some hours" as I have, it's just for my convenience in being able to work on this in steps as life allows, and may only be possible because I'm not using any accelerants.
Also note that my process of mixing is much more lengthy than Karl's, with heating the mix and slowly adding more water bit by bit during the initial stirring of lye and binder zeolite to wet it, then having to scrape/stir to remove and re-integrate as much of the "baked-on" binder off the bottom of my biggest stainless spaghetti pot as I could before letting it cool and rest until I next have time to work on it.
Bottom line, I am making it more complex than Karl advises is necessary, and have no comparison tests of process to show that there is any benefit with this binder to longer rest times, or "heating while slowly going from barely saturated crumbly mix to a pasty consistency, somewhere between mayo, and peanut butter in a cool room", beyond the benefit of the heat generated by the lye and water mixing in the initial wetting of the binder, provides any actual advantage.
Part of the reason, is that I am not sure of the completeness of the dissolution of dissolvable minerals from my zeolite, as the mix always remains grainy. Dissolving the small .1 mm granules and down should be possible, even easy, according to Karl, and if the zeolite was micronized I would never perceive grainy-ness in the mix even if some particles/types
mineral inclusions are undissolved at the reccommended lye concentration.
My binder process for this latest batch was mixing with a single kitchen mixer blade in a drill at first, while adding water just until it was all damp... Still crumbly... not sure if all lye was dissolved at that point or not, but wanted to extend time that at least some of the coarse powder zeolite was exposed to very high alkalinity, to hopefully promote more mineral dissolution.
It got very warm during the grainy stage and stayed warm as I added the remaining portion of 1 litre of water, being about 150F when I finished, at which point it was "gritty peanut butter in a cool room" consistency.
Then I tried to maintain that heat, switching to mixing with a butter knife first on too high-heat a burner, and "baking" some of the zeolite lye mix to the bottom of the pan, then resting a couple of hours of mostly low input heat on simmer on my ceramic top range, with infrequent stirring for the first hour, by hand with a butter knife, and almost constant stirring in the second hour, scraping and re-integrating as much of the dried/baked on binder from the bottom of my big spaghetti pot as possible, before turning off the heat and retiring for the night.
I am also very interested in trying the zeolite and feldspar combo Karl recommended for a paint-thin "heat-hardening" mix with which to turn mineral wool into a ceramic fiber blanket like refractory insulative fill, hopefully with performance somewhere near current pre-formed ceramic fiber tube options, that could be formed to whatever desired shape in any thickness, cheaply, then dried (and pre-fired if needed) before use in the stove, or heat cured in place during stove operation
Perhaps 4 of my 3"thick by 15" wide by 48" long mineral wool blankets wetted and dried/cured into a single square refractory tube, could be an easy, sufficiently insulative, low mass and refractory riser, stiffened and heat hardened with the zeolite/feldspar GP, and able to beat thinner walled formed ceramic fiber tube sections on price to performance basis.
All of this depends on my testing of the material and confirmation of long term refractory suitability/performance in the days, weeks, and months to come.
If I left any questions unanswered, or inspired new ones about my process and thinking, ask away! (Perhaps better to do so in my own Zeolite Geopolymer thread, and I will be CC'ing your full question and this answer to that thread as well, for continuity of information on my zeolite GP experiments, and to not clutter this post about a different binder and aggregate combo with more discussion of my own.
Also, Karl, if any of my statements here about my thinking regarding my materials or process, or my binder mixing process analysis/advice here or to esborjaneer in my zeolite GP experiment thread, seems incorrect please correct me in whichever threads are appropriate to the needed correction.
Thank you in advance :-)