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Post by etownandrew on Jan 13, 2018 6:32:46 GMT -8
I have spent a few hours this morning searching the internet and reading Kaolin based Geopolymer studies. One interesting note is that in each study they mixed the activator/binder and let it sit for 24 hours before using. One study added the additional note that the activator was to sit 24 hours and then be used within 36 hours. I don't know how much difference this makes. None of the studies justified their use of a 24 hour period. It was just presented as part of their documentation of their experimental methods. I presume it might track back to an earlier study that worked this out originally. Or it might be some sort of common knowledge for chemists. Here is a link to a folder containing the studies that I downloaded drive.google.com/drive/folders/1Sexg3Qpu43vLLWwk9XJHHQW7vdvQ-yPR?usp=sharing |
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Post by coastalrocketeer on Jan 13, 2018 7:15:36 GMT -8
I have spent a few hours this morning searching the internet and reading Kaolin based Geopolymer studies. One interesting note is that in each study they mixed the activator/binder and let it sit for 24 hours before using. One study added the additional note that the activator was to sit 24 hours and then be used within 36 hours. I don't know how much difference this makes. None of the studies justified their use of a 24 hour period. It was just presented as part of their documentation of their experimental methods. I presume it might track back to an earlier study that worked this out originally. Or it might be some sort of common knowledge for chemists. Here is a link to a folder containing the studies that I downloaded drive.google.com/drive/folders/1Sexg3Qpu43vLLWwk9XJHHQW7vdvQ-yPR?usp=sharingOr that it was found that the longer the better, up to a point, but that the 8 hour work day was not as good as 24, but better than 48, so they chose that for expedience and time management. Mix a batch when you get to work at 9, and subsequent batches until finished, or you run out of time in the work day. The next day you show up and do your aggregate water and aggregate additions for each batch, in succession, 24 hours after it was mixed. Besides expediency, this would allow the rest period to be kept sufficiently uniform to keep it from being a factor in differences observed. I would imagine the optimum rest time would vary and have to be found separately for each experimental mix, based on the binder materials elemental content, reactivity, total particle surface area (finer particles are more accessible for chemical attack), as well as the type and concentration of geopolymerization agent chosen (acid or alkali to break down the minerals and prepare the solution that will polymerize) I would imagine mixes of some highly reactive materials go off so fast that you would come back the next day to find you had hardened pots of binder on your hands. In the ones I have read, they are often also curing their geopolymer test samples in fairly high heat conditions, sometimes higher than a home oven will reach. Interesting subject for sure. If we cannot find any source of the 24 hour rest being proven better than other time intervals, I would have to assume it was for convenience of being able to keep the rest period uniform, but not have to somehow mix all your samples at the exact same moment, and then do your aggregate final additions to all batches at the same time the next day. |
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Post by Deleted on Jan 13, 2018 10:43:40 GMT -8
Standard waterglass has very large molecules.
If the waterglass is mixed with lye it will react with the lye
and be broken up to smaller more reactive molecules.
The concersion to smaller molecules takes time,
therefore the 24h rest.
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Post by smartliketruck on Jan 13, 2018 11:11:54 GMT -8
The time is to allow dissolution into simpler molecules. If you add more energy either heat or mechanical (high shear mixing) you will shorten the time needed to achieve the desired level of dissolution.
If you are making an initial binder solution of say 50/50 kaolin and lye mixture there is little chance of it "going off" as too much lye will have a poisoning effect on polycondensation and it will stay in simpler solutes.
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Post by coastalrocketeer on Jan 14, 2018 0:34:05 GMT -8
Standard waterglass has very large molecules. If the waterglass is mixed with lye it will react with the lye and be broken up to smaller more reactive molecules. The concersion to smaller molecules takes time, therefore the 24h rest. Would this benefit a solution made with the TSP 90 sodium metasilicate, or is it only beneficial for water glass produced by other means? |
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Post by branja on Jan 14, 2018 3:05:30 GMT -8
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Post by branja on Jan 14, 2018 3:20:01 GMT -8
By adding NaOH or KOH in liquid WG you will increase pH and alkali/Si ratio. Therefore "increase the ratio of small chains-monomers / large-chains-cyclic molecules" As Karl said ,you will have more Si small molecules then Si large molecules. Downside is that high pH WG or your TSP will seregate (start to make solids) if it is left for some time.
This is for liquid silicates. Solid WG/silicates are a bit different. Im assuming your TSP is a powder?
Edit : google says: TSP 90= it is a powder ,mainly of Sodium metasilicate pentahydrate /Disodium trioxosilicate .
In "pseudo speak", descriptively (non chemist way) SiO3 and some Na , H2O in a solid form. So if you dilute it in H2O, it will form a Na and SiO3 solution in H2O. SiO3 will spontaneously "go around" and make chains with himself -more or less, depending on Na(pH) and H2O(can it move around?) content. So you made something very much like liquid WG.
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Post by Deleted on Jan 14, 2018 7:18:49 GMT -8
Would this benefit a solution made with the TSP 90 sodium metasilicate.... Sodium metasilicate is already the smallest molecule, though it could be turned into sodium orthosilicate which contains more sodium and thus has a higher PH and is more aggressive. The higher PH of sodium orthosilicate would retard the geopolymerization. User friendly agents are mixtures of metasilicate and larger molecules. |
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Post by coastalrocketeer on Jan 14, 2018 12:52:01 GMT -8
Would this benefit a solution made with the TSP 90 sodium metasilicate, or is it only beneficial for water glass produced by other means? Yes &no. You cant just say benefit. Diferent pH makes diferent types of coumponds more or less present. High pH promotes smaller/simpler compounds of Si. It will be probably clear to you from a PDF from SPRINGER "chapter 2 Precursors and Additives for Geopolymer Synthesis" I don't have a full title of the book,Google it Thank you branja! I don't think that was in my collection of geopolymer related files... And not sure if I have ever seen it before but even though it concerns a material I will probably never use as my area has a lot of hydro power and no coal plants, it looks a lot more accessible and applicable in it's descriptions of things than many of the research papers I have perused... I'll put it this way... It's easier trying to understand what Karl so graciously tries to impart to me, and all of us, with no chemistry or geology background, and two different mother tongues between us, than interpret the implications of some of the papers that are more specific in their discussion and application. (And thank GOD Karl has a good grasp of the English language or there would be no communication with me at all, because my German consists of having successfully translated a "nein danke nuclear" bumper sticker after seeing one and having already been familiar with the English version!) LOL! Your response and pointer to pertinent information is VERY much appreciated And your edit to add explaination in non chemist "pseudo speak" was exactly what this chemistry dummy needed! |
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Post by coastalrocketeer on Jan 14, 2018 12:52:27 GMT -8
Would this benefit a solution made with the TSP 90 sodium metasilicate.... Sodium metasilicate is already the smallest molecule, though it could be turned into sodium orthosilicate which contains more sodium and thus has a higher PH and is more aggressive. The higher PH of sodium orthosilicate would retard the geopolymerization. User friendly agents are mixtures of metasilicate and larger molecules. Thank you Karl! |
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Post by branja on Jan 15, 2018 8:34:32 GMT -8
Just a quick question,maybe off topic:
Sodium orthosilicate, this one?
Na O Na
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O-Si-O
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Na O Na
Would not that be a solid crystal on room temp ,if the material in mind would be soley made of Sodium orthosilicate ?
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Post by Deleted on Jan 15, 2018 9:03:23 GMT -8
Oxigen has two bonds and thus cannot hold two atoms if already bond to a third.
Sodium orthosilicate formula Na4O4Si .
One silicon atom binds 4 negative oxigen atoms of which each binds one positive sodium atom.
In absence of a solvent all alkali silicates are solids at room temperature.
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Post by esbjornaneer on Jan 17, 2018 0:51:33 GMT -8
I have to admit to not having read the original link in this thread.
Karl would you give a recommendation for resting time for 'pure' fire clay/caustic soda binder (no water glass)?
And also micronized zeolite/caustic soda?
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Post by Berend on Jan 17, 2018 2:22:23 GMT -8
I'm using feed grade clinoptilolite zeolite which is a very fine powder. A few days ago a made a very small test using 6g zeolite, 2g naoh and 2.5g water. After mixing I put the container with this binder in a crock pot with a temperature of about 65C-75C. I don't remember exactly how long I left it in there but it was less then 30 minutes. But that was already enough to stiffen up the binder in such a way that I could not use it anymore with the aggregate I planned on using.
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Post by Deleted on Jan 17, 2018 8:19:28 GMT -8
Where did you get feed grade clinoptilolite zeolite and at which price ?
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