Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 11, 2016 4:53:40 GMT -8
The geopolymer brick LTGS. www.geopolymer.org/fichiers_pdf/ltgs.pdfThe paper linked above says: The oligosialate geopolymeric precursor ( binder ) contains 50% by weight of NaOH, KOH equivalent. Thus to obtain the binder mix one part calcined clay with one part lye with just enough water to dissolve the lye and let it rest some hours. As my experiments have shown calcining is not the only way to obtain Meta-Clays with very high reactivity.donkey32.proboards.com/thread/2057/acid-activated-geopolymersWet activation by organic acids works with virtually any type of clay. As far I can tell, without expensive laboratory equipment: Reactivity on the level of highly reactive commercial metakaolins like MetaStar 501 or Argical M 1000 is possible.As I have no red clay cheap white clay was used for the proof of concept. Activation was performed with cheap ordinary vinegar, then the activated clay was mixed with lye flakes 1/1 by dry mass and set aside to rest some hours.
The ready binder was then mixed with nine times more clay by weight, which equals 5% activated clay and 5% lye, and just enough water to make it easy kneadable.
The mixture was molded, dryed and finaly heated to 250°C, which turned the mixture to strong, hard and water insoluble stone, with a dry density of 1.35g/cm³.
The density of 1.35g/cm³ indicates a porosity pretty close to the requirement for an aerogel, despide the low amount of water used as there is no waterglass to fill the space between the clay particles. With slightly more water an aerogel should be possible in this way.
Binder content above 10% should allow to make mixtures liquid enough to be castable.
The LTGS paper claims with lateritic earth 2% to 5% binder are sufficient for water stable bricks. which equals 1% to 2.5% of lye.
It may even work to mix preactivated clay with high amounts of ash from hard wood or straw.
A Study on Wood Ash Based Lye as Alkaline Activator in Geopolymer Concrete. www.ijirset.com/upload/2015/december/172_46_A_Study_on.pdf
Alkali Content and Slagging Potential of Various Biofuels. cta.ornl.gov/bedb/biopower/Alkali_Content_and_Slagging_Potential_of_Various_Biofuels.xls
The potential of use as a Permaculture building material is high.
Davidovits has two LTGS brick videos at youtube. www.youtube.com/watch?v=zjeVeDVtghc www.youtube.com/watch?v=uq4T7p5RAiA
|
|
|
Post by firewatcher on Sept 13, 2016 7:21:19 GMT -8
The geopolymer brick LTGS. www.geopolymer.org/fichiers_pdf/ltgs.pdfThe paper linked above says: The oligosialate geopolymeric precursor ( binder ) contains 50% by weight of NaOH, KOH equivalent. Thus to obtain the binder mix one part calcined clay with one part lye with just enough water to dissolve the lye and let it rest some hours. As my experiments have shown calcining is not the only way to obtain Meta-Clays with very high reactivity.donkey32.proboards.com/thread/2057/acid-activated-geopolymersWet activation by organic acids works with virtually any type of clay. As far I can tell, without expensive laboratory equipment: Reactivity on the level of highly reactive commercial metakaolins like MetaStar 501 or Argical M 1000 is possible.As I have no red clay cheap white clay was used for the proof of concept. Activation was performed with cheap ordinary vinegar, then the activated clay was mixed with lye flakes 1/1 by dry mass and set aside to rest some hours.
The ready binder was then mixed with nine times more clay by weight, which equals 5% activated clay and 5% lye, and just enough water to make it easy kneadable.
The mixture was molded, dryed and finaly heated to 250°C, which turned the mixture to strong, hard and water insoluble stone, with a dry density of 1.35g/cm³.
The density of 1.35g/cm³ indicates a porosity pretty close to the requirement for an aerogel, despide the low amount of water used as there is no waterglass to fill the space between the clay particles. With slightly more water an aerogel should be possible in this way.
Binder content above 10% should allow to make mixtures liquid enough to be castable.
The LTGS paper claims with lateritic earth 2% to 5% binder are sufficient for water stable bricks. which equals 1% to 2.5% of lye.
It may even work to mix preactivated clay with high amounts of ash from hard wood or straw.
A Study on Wood Ash Based Lye as Alkaline Activator in Geopolymer Concrete. www.ijirset.com/upload/2015/december/172_46_A_Study_on.pdf
Alkali Content and Slagging Potential of Various Biofuels. cta.ornl.gov/bedb/biopower/Alkali_Content_and_Slagging_Potential_of_Various_Biofuels.xls
The potential of use as a Permaculture building material is high.
Karl, I haven't read the linked paper yet, but is there a reason why one would not just activate 100% of the clay to be used? Do you think that it may be come too reactive causing casting problems? Too much water perhaps?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 13, 2016 8:09:18 GMT -8
I have only tried stay as close as possible to the original recipe, which is focused on keeping the costs as low as possible.
For more liquid, castable mixtures with a higher binder content of 25%-30% (lye 12.5%-15%) it should help to activate the rest of the clay too. 1% acid per weight would likely suffice for this purpose.
Wet activation with small amounts of acid is much cheaper than calcining at high temperatures, much simpler as well.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 18, 2016 5:00:53 GMT -8
I have prepared a LTGS mixture with 30% binder. This time I have also activated the rest of the clay with 2.5% acetic acid by dry weight. Then I have filled the mixture with four times by dry weight fine slag sand. I have used just enough water for a thick paste only flowable under beating or vibration. The result is water stable but such a high load makes it relatively brittle. At this ratio 33kg refractory can be made with 1kg of lye and 167g acetic acid. 30% binder and three times slag sand would be less brittle and still give 27kg/1kg lye. 20% binder and two times slag sand would give 30kg/1kg lye.
The possible ratio of aggregate/geopolymer depends on the particle size. Larger particles allow a higher ratio. The largest possible ratio requires coarse, medium and fine particles, however this would also cause a much higher thermal conductivity.
Together with a LTGS mixture waterglass with low solid content could be used to make castable mixtures with high agregate content less brittle.
|
|
|
Post by firewatcher on Sept 20, 2016 9:58:43 GMT -8
@karl, So my first step to try this out with a proper material (non-bentonite) is selecting a clay to use...the ball clay or 200 mesh kaolin?
How long did you let the molded material dry for before heat curing and how thick was the mold?
Would a heat cure at temperature above 250C not be advisable right away? Is a ramp-up to higher temps needed if doing so (I'm thinking of my only temperature curing option - camp fire)?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 20, 2016 10:43:28 GMT -8
Ball clays have a very small average particle size usualy below 1 micron and thus a high water demand, which increases the risc of cracks. The particles of kaloin clays are larger and thus the water demand of kaolin clays is much lower.
Clays can be mixed with feldspar or Pyrophyllite (Pyrotrol) which have much larger particles to reduce the water demand. The prices for feldspar are similar to kaolin. However at ROVIN you need to buy at least 100lb to get a low price for virtually everything.
ROVIN sells fire clay with 40 and 50 mesh, maybe milled mudstone. Such a clay is not available here, thus I cannot say how it may behave.
My test pieces have a thickess between 17 and 22 mm, depending on the water demand.
As I have cured my pieces in an oven I could slowly raise the temperature starting at 50°C. Only the samples with bentonite I have dried at ambient temperature for a day or more, up to one week.
If a geopolymer contains still a lot of water when heated the inner structure can be damaged by steam pressure.
|
|
|
Post by firewatcher on Sept 20, 2016 16:10:04 GMT -8
I have prepared a LTGS mixture with 30% binder. This time I have also activated the rest of the clay with 2.5% acetic acid by dry weight. Then I have filled the mixture with four times by dry weight fine slag sand. I have used just enough water for a thick paste only flowable under beating or vibration. The result is water stable but such a high load makes it relatively brittle. At this ratio 33kg refractory can be made with 1kg of lye and 167g acetic acid. 30% binder and three times slag sand would be less brittle and still give 27kg/1kg lye. 20% binder and two times slag sand would give 30kg/1kg lye. The possible ratio of aggregate/geopolymer depends on the particle size. Larger particles allow a higher ratio. The largest possible ratio requires coarse, medium and fine particles, however this would also cause a much higher thermal conductivity. Together with a LTGS mixture waterglass with low solid content could be used to make castable mixtures with high agregate content less brittle. @karl,
I'm misunderstanding something I think...
I'm not sure from your mix mentioned above, how the 30% binder is calculated...wouldn't a slag/binder ratio of 4/1 mean that the mix is only 20% binder?
The rest of the mix I think that I've figured out correctly:
33 kg of refractory mix:
use of 1 kg of lye leaves 32 kg remaining with a 4/1 slag to clay ratio: 25.6 kg slag 6.4 kg clay
the clay is activated in 2 parts (10% of clay with 5% acetic acid and 90% of clay with 2.5% acetic acid) 0.64 kg of 5% acetic acid activated clay 5.76 kg of 2.5% acetic acid activate clay total clay = 6.4 kg
acetic acid content: 0.032 kg of acetic acid used in 0.64 kg of clay for activation 0.144 kg of acetic acid used in 5.76 kg of clay for activation total acetic acid = 0.176 kg
How did I do?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 20, 2016 16:44:09 GMT -8
30% binder means 15% clay and 15% lye in the binder plus another 70% clay. With only a 3/1 ratio it becomes not much stronger. Obviously a lot aggregate requires some waterglass.
|
|
|
Post by firewatcher on Sept 21, 2016 5:24:37 GMT -8
30% binder means 15% clay and 15% lye in the binder plus another 70% clay. With only a 3/1 ratio it becomes not much stronger. Obviously a lot aggregate requires some waterglass. @karl,
So I redid the math per your clarification at it looks like my numbers actually match yours now...
33 kg of refractory with a 4 parts slag/1 part binder:
26.667 kg slag 1 kg (15% clay) activated with 5% acetic acid 1 kg (15% lye) 4.667 kg (70% additional clay) activated with 2.5% acetic acid 0.050 kg acetic acid for the 1kg of clay 0.117 kg acetic acid for the 4.667kg of clay total acetic acid = 0.167 kg
Now, for the question of the day...is it possible to substitute citric acid for the acetic acid in the mix? I've been looking online for "brick and mortar" store sources of acetic acid and am having difficulty finding any place that sells it. I know that I can get citric acid at the local home brewing shop.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 21, 2016 6:09:25 GMT -8
Citric acid or acetic acid both work. Use whatever you can get cheaper. 0.167 kg acetic acid is less than 4 liter 5% vinegar.
As a castable LTGS mixture obviously requires additional waterglass for high strenghs, a 10% LTGS mixture with waterglass would suffice.
You may test if you can add about 30% aggregate to a 10% ram mixture without weakening it to much, which would give you 26kg refractory with 1 kg lye.
|
|
|
Post by firewatcher on Sept 21, 2016 6:58:08 GMT -8
Citric acid or acetic acid both work. Use whatever you can get cheaper. 0.167 kg acetic acid is less than 4 liter 5% vinegar. As a castable LTGS mixture obviously requires additional waterglass for high strenghs, a 10% LTGS mixture with waterglass would suffice. You may test if you can add about 30% aggregate to a 10% ram mixture without weakening it to much, which would give you 26kg refractory with 1 kg lye. Of the two materials, I was only able to find citric acid in solid form (1 pound/ $5), again looking only at "brick and mortar" locations. In the mix, the porportions are for solid forms of the acids correct? Just to clarify as well, 10% LTGS means 5% clay +5% lye + another 90% clay?
|
|
|
Post by firewatcher on Sept 21, 2016 7:04:18 GMT -8
How quickly I can make test pucks will depend on how soon I can get to the ceramics supply shop (I think that I've settled on using the kaolin clay that you mentioned in past posts in the geopolymer thread). As it may take a little time before I'm able to make it to pick up some kaolin, I may try this out in the mean time with bentonite...just because i have it on hand.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 21, 2016 7:22:21 GMT -8
Yes, 10% LTGS means 5% clay +5% lye + another 90% clay. You can mix vinegar with water for lower percentages. The only difference to the solid form is that the vinegar contains impurities. I have not noticed any negative effects from the impurities.
You could test your fire clay. If it is normal clay and not some grinded mudstone it should work.
|
|
|
Post by firewatcher on Sept 21, 2016 8:28:14 GMT -8
Yes, 10% LTGS means 5% clay +5% lye + another 90% clay. You can mix vinegar with water for lower percentages. The only difference to the solid form is that the vinegar contains impurities. I have not noticed any negative effects from the impurities. You could test your fire clay. If it is normal clay and not some grinded mudstone it should work. @karl, How are you adding acetic acid to your mixes (using vinegar or concentrated solid acetic acid)? I thought that the amount of acid had to be added in dry weight (using solid concentrated form). Is this not correct?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 21, 2016 8:44:37 GMT -8
All the LTGS mixtures I have tested so far cheap oddinary vinegar with 5% acetic acid content was used. For 5% add winegar with the weight of the clay, for 2.5% only half the vinegar and fill it up with water if needed. I am testing things for practical use and try to keep (my) costs low,
|
|