Coastal’s kaolin geopolymer experiments

[coastalrocketeer]

Thank you Karl for all of your information provided in this forum and guidance in my past, limited experimentation.

I recently aquired additional materials :-)

1 cubic yard of volcanic red cinder rock track sand I intend to use as cheap, lightweight, high volume filler aggregate, perhaps only in lower temp areas of the stove, based on mix testing results.

8 - 50lb bags of Black Diamond Fine coal slag blasting abrasive FAQ says "The grit is a mixture of 30/60 and 40/80 mesh." (higher temp aggregate?)

4 - 50lb bags of McNamee Kaolin

2 - 50lb bags of EP Kaolin

2 - 50lb bags of Spectrum Sodium Nepheline Syenite A-270

2 - 50lb bags of Lincoln 60 fireclay

2 - 50lb bags of custer feldspar 200 mesh

1 - 50 lb bag of Mora-Leaf P&K monopotassium phosphate based fertilizer
ag.wilburellis.com/Products/Product%20Documents/PlantNutritionPRODUCTBULLETINS/ProductBulletin_Mora-Leaf_P-K_K-1213-339.pdf

1 - 50 lb bag Type S hydrated mason's lime

Plenty of portland cement

As much aluminum foil as I need

Rockwool batt insulation.

Alkalines:
NaOH - about 4lbs on hand at the moment
KOH - 2lbs
Can order more of these as needed based on needs of any successful mixes I work out using combinations of these ingredients.
Acids:
15 lbs of ascorbic acid/vitamin C
As much 5% vinegar as I need can be obtained
Phosphoric acid - I have one gallon of First Street Lime and Scale remover which is a “proprietary” concentration of phosphoric acid in water. I used a calculator online and by measuring the weight of 100ml of the solution, and it’s temperature was able to determine that it is about 30% phosphoric acid by weight. At less than $10 a bottle it is a lot cheaper than the Ospho I was going to try, which is 45%, but $30 a gallon, and contains something called dichromate

Still have a little under 120lbs SweetPDZ Zeolite powder
35 lbs of bentonite clay clumping cat litter
About 3.5 lbs of Red Devil TSP/90 (solid waterglass)
About 8 lbs of washing soda

Am hoping to experiment with acid activation as well as alkaline and looking forward to better results than I was obtaining with bentonite and zeolite alone.

In my most recent experiments I found even the children's air-dry modeling clay from my daughter's younger years produced much more satisfying results than bentonite alone, so I am looking forward to working with high alumina kaolins for refractory purposes.

I am reading through all of the past threads you posted on various ways to use these feedstocks, and coming up with ideas and ranges of materials to try with what I have to work with, and am hoping to bounce ideas off of you and obtain further suggestions and guidance for mix design improvemtns, as I proceed.

Below I will be aggregating information on the various ingredients I have, and pertinent info Karl and others have provided here, and in other places around the web.

I am also going to ask Peterberg to “pin” certain threads (mostly Karl’s) in this Geopolymer forum, to ease location of the most critical posts to the first page, and keeping them above my, and others, experimentation threads. (I will however, definitely be requesting Sksshel’s Kansas City #1 thread be pinned, as it is the first successful geopolymer core formula from this forum produced from Karl’s continued efforts to enlighten and inspire us all.)
So I will create a list in a subsequent post of things I think should be pinned, and will incorporate the suggestions of others, run it by Karl, then make the request to Peterberg after done, so we only have to bother him once, with a complete list of what should be pinned at the moment.

[coastalrocketeer]

RE: NEPHELINE SYENITE Karl said:

<<<>>>

Weak acids combined with micronized basic stone flour like nepheline syenite or basalt can be used as geopolymeric binder as well.
Citric acid alone can make it sufficiently water resistand to pass the submerged water test.
Applying the extreme chemical attack similar to a LTGS binder can improve the outcome.
Additional phosphoric acid gives extreme water resistance.
Phosphoric acid alone does not nearly perform as well,

Nepheline syenite is relatively cheap and available from virtually any pottery supply.

<<<>>>

Kaolin can be mixed with nepheline syenite and in this way be hardened with acids.
The obvious advantage is that no extremely aggressive chemicals are required,
and may also be cheaper.
Acid based mixtures need some phosphoric acid or monophosphate for high water resistance.

Kaolin can also be used for mixtures with soda ash or potash and monophospate with caustic lime as accelerator.

<<<>>>

A a 1/1 mixture of nepheline syenite and clay can be hardened with 4% citric acid.
all figures by mass.
Clays with a high potassium content work especially good with acids.
The water resistance will be lower than with the lye based receptures,
but some additional phosphhoric acid can increase that.
Anyway stoves are rather seldom submerged in water.

Likely Monopotassium Phosphate could be used instead of the phosphhoric acid to improve water resistance,
but I have not tested this combination with citric acid.

<<<>>>

On making talc based soapstone equivalents:

E Said: So reading the second scientific article I find they used:

90% Talc with 10% MgO increased compressive strength compared with 100% Talc (i.e. 90g talc + 10g MgO)
40% of dry matter weight as water (i.e. 40g water)
40% of talc+MgO dry weight as phosphate (potassium phosphate / potassium dihydrogenophosphate) (i.e. 40g phosphate)

Karl said:
You quote the second, not the first.
The first deals with raw talc the second with calcined talc.
The difference in reported strength is neglible.

karl said:
I've just done some rough testing to see if it is possible,
thus I have no specific recipes.

I did the tests with phosphoric acid, calcined magnesium oxide and raw talc.
In anothe test I have replaced the MgO with nepheline syenite,
wich is much cheaper and easier to handle.
The results were similar to the results reported in the two papers.
The result with 30% nepheline syenite was the most satisfying.

E said:
Comparing their recipe, (MgO/KH2PO4=1/4=0.25), with your suggestion, molar 1/1 ratio (MgO/KH2PO4=40/136=~0.294), you advice slightly more MgO than they used. Would you recommend I still use 10%MgO/90%talc in the aggregate or 100% talc?

Karl said:
With 10% MgO you can expect an increase of compressive strenth of about 15% and about 35% with 20% MgO.
Nevertheless even with 20% MgO the strength remains rather low.

E said:
So they used no plasticiser. And if I understand correctly they mixed KH2PO4 and water, then added talc and MgO, no mention of binder pre-mix.

Karl said:
Superplasticiser are used to increase compressive strenth by saving water.
(Note from edited out discussions: Use one without sulphates)

<<<>>>

firewatcher kaolin refers always to natural kaolin.
Natural kaolin clay is not very plastic,
thus if a kaolin is termed as plastic it is very likely a designer kaolin.

The problem for people located in the US are the insane prices.
Looks like capitalism does not work well in the US.
In Germany I can usualy get clays, grog or stone flour
for roughly half the price requested in the US,
even if it has been shipped over an ocean.

Grog mixtures are the simplest and although grog is relatively expensive
still cheaper than commercial refractory mixtures.
Quick lime works best as an accelerator.
Hydrated lime works best if slacked for at least five years.

A mixture of 1/3 nepheline syenite and 2/3 clay can be hardened with about 4% citric acid.
A one by one mixture will be significantly stronger.
The result will not decay in water but becomes rather weak it saturated with water.
Not a real problem, as in a stove this should never happen.

With additional phosphoric acid the result will become much more water resistant
and also significantly stronger.
Geopolymers with phosphoric acid adhere much stronger to surfaces,
thus surfaces should be very smooth and the use of a release agent is recommented

Nepheline syenite is not expensive and due to the very much lower water demand
in an acidic environment even cheap ball clays may become useable.

<<<>>>

DigitalFire Material Database Link
digitalfire.com/4sight/material/nepheline_syenite_a270_2963.html
Nepheline Syenite A270
Alternate Names: Spectrum Nepheline Syenite,
Nepheline Syenite Spectrum

Oxide Analysis Formula
CaO 0.35% 0.027
MgO 0.02% 0.002
K2O 4.80% 0.224
Na2O 10.50% 0.746
Al2O3 23.60% 1.019
SiO2 60.20% 4.412
Fe2O3 0.08% 0.002

LOI 0.42
Oxide Weight 438.46
Formula Weight 440.31

Also available in 200, 400 grades (other grades are available for other purposes).

From Unimin data sheet: SPECTRUM® ceramic fluxes are produced from nepheline syenite; a naturally occurring, silica deficient sodium-potassium alumina silicate. The higher total alumina and alkali contribution available from nepheline syenite produces ceramic ware with greater impact and flexural strength and improved resistance to the stresses of thermal extremes and mechanical shock.
The lower melting eutectic and increased fluxing power of SPECTRUM® make possible body compositions which mature at temperatures as low as cone 3-5. It is the higher alkali to alumina ratio and greater chemical reactivity that accelerate the melt and promote a faster maturation. SPECTRUM will increase the rate of vitrification over a wider firing range, ensure smooth glazed surfaces even at lower temperatures and help to reduce the deformation typically encountered in fast fire cycling. When the objective is improved translucency, SPECTRUM will combine with and consume the available free crystalline silica to create highly translucent wares.

Particle size (% retained on):
200 mesh: 0.05
270 mesh: 0.67
325 mesh: 1.29

Melting point: 1868F/1020C
pH: 10.1
Bulk Density (lb/ft3): 38-55
Specific gravity: 2.61

[coastalrocketeer]

RE: FELDSPAR Karl said:

<<<>>>
In Acid Activated Geopolymers, Karl said:

I have mixed 60g bentonite with 30g of either zeolite, feldspar or clay,
then acid activated the mixtures with each 5g citric acid.
Later I have added powdered waterglass, lye and 300g slag sand
and mixed all with waterglass and finally the usual amount of cement.
All three mixtures worked well and were faster to cure and dry than
the mixture with 100g pure acid activated bentonite.
Resulting dry densities around 1.4.

The logical next step is acid activation of other clays.

<<<>>>

In Karls LTGS Brick, Ram Mass: Dirt Cheap Geopolymer Refractory, Karl said:

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.
<TRIM>
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.

<<<>>>

<<<>>>


digitalfire.com/4sight/material/custer_feldspar_253.html
Custer Feldspar
Potash Feldspar
Alternate Names: Custer Spar

Oxide Analysis Formula
CaO 0.30% 0.033
K2O 10.00% 0.664
Na2O 3.00% 0.303
Al2O3 17.00% 1.042
SiO2 68.50% 7.128
Fe2O3 0.10% 0.004

LOI 0.30
Oxide Weight 618.54
Formula Weight 620.40

DENS - Density (Specific Gravity)
Sp VAL
1 2.6
SIEV - Sieve Analysis 35-325 Wet
Sp TOT 100M 150M 200M 325M NOTE
1 100 0.3% (0.5% max) 4% (5% max)
pHPW - pH for dry powder
Sp Valu
1 8.0
This is one of the main feldspars used in the ceramic industry in North America. It is used in industries such as abrasives, sanitary ware, floor and wall tile, dinnerware, pottery, and electrical porcelain. It is a ceramic grade, high potash feldspar and is available in crude, 200, 325 mesh and chip form.

[sksshel]

I look forward to following your progress.  Let me know if I can help in any way. 

[coastalrocketeer]

Clinoptilolite Zeolite



Another sample

[coastalrocketeer]

Here is the stack of experimental mixes I made over a few evenings last week.

oven cured with lids on at 150-170 from 2-6 days, until the 8th, and then open lid cured at ambient temps until being moved to the stove top this evening (double walled stove, we can dry wood on top and it never browns at all.)


Samples sitting on top of stove.^^^


Yellow Lab enjoying the warmth and being his lovable attention seeking self... :-)  ^^^

[coastalrocketeer]

I have found that I need to experiment more with the zeolite binder making to optimize my technique, as I was never able to achieve complete dissolution of graininess in the binders and wind up with it thickening so much in my attempts to minimize water addition during that dissolution stage, that it becomes like hard taffy and is hard to dissolve into a thin gravy again where aggregates can be mixed in. The time I achieved nearly complete dissolution of the zeolite and what felt like a really good binder consistency when I got tired after mixing the binder zeolite and left the plastic tub in the oven at 170 overnight.

It became MUCH thicker... when I pulled it out of the oven hot, it was like hot taffy, still stirrable, but much thicker than honey. And before I even got to add water it cooled and became hard enough at under 100F that mixing it with additional water for aggregate addition was very slow and difficult. It was very similar to room temperature taffy.
The “graininess” of the zeolite did seem greatly reduced, and dissolution increased, so I will try again with a little more continuous attention to the mix and making minimal but timely additions small amounts of hot H2O as it thickens.

[coastalrocketeer]

My next mix I will try to achieve high concentration and excellent dissolution without allowing over thickening in the binder mix while doing so...

  the one that dissolved really effectively in the oven overnight had to be peeled from the container after I got the edges broken free...  just getting the plastic spoon out of the mass was difficult once it had cooled...  I presume I need to increase dilution before letting it cool and it should be easier.

[coastalrocketeer]

peterberg - sorry to bother you, but I can’t figure out how to do so myself... if it is possible, can you rename this thread “Coastal’s kaolin geopolymer experiments, next time you are on doing admin stuff?

Thank you!

[coastalrocketeer]

Well, I achieved good dissolution with KOH, using added heat on a little plug in electric hot plate with an actual thermostatic control. (My ceramic range top merely changes duty cycle of the element to vary heat output, and only max temperature is actually controlled by a temp over limit device built into the element.) with this one I can actually control temp of the plate down to about 120-140F.

However, I am finding even going outside for 10 minutes for a cigarette can leave me with a hard taffy mass that is a pain in the ass to re-solve into a solution. Live and learn.

That next set of mixes is actually going to go in my acid activated thread. Named ABE-1-PC, and ABE-1-HL.

[coastalrocketeer]

I have replicated Steve’s Kansas City #1 mix with the EP Kaolin, and the Moraleaf P&K I procured in place of actual Monopotassium Phosphate. It was the closest I could find at retail here in Oregon. The bag says it is derived from Monopotassium Phosphate.

Actual MKP is 0-52-34 (52% potassium, 34% phosphorus by weight)
Moraleaf P&K is 0-50-33, so hopefully close enough. (I probably should have used about 2% more P&K to make up for the lower percentages, but followed the recipe as it was, despite my substitution. This one will have to cure a good while, as I am letting it do so at the ambient temps in my house (60-70F)

[coastalrocketeer]

7 or so samples that I demolded in the last couple of days are currently being dried in the oven at 170F. I will give them 1 hour at 170F then weigh them to see when they stop losing water as I increase temp 50F at a time as Karl has suggested elsewhere.

[coastalrocketeer]

Samples are dry... now to figure out what tests I want to do on them

[coastalrocketeer]

First am going to figure out a way to accurately measure volume so I can compute grams/cc dry sample weight.

[Jura]

I was to delve into geopolymers but.. life is so short :-( and there is too many things to do :-)

I tried to figure out what's your aim with geopolymers.
Are you trying to figure out a workable recipe for a high temp brick (chamotte replacement) or one for an ordinary brick ?

what are your source of the materials ?
(https://digitalfire.com/4sight/mineral/index.html)?