LTGS from expanding/shrinking clays such as launa in Spain

[esbjornaneer]

Hello Karl,
I have more questions for you regarding using expanding/shrinking/launa clay for LTGS.

My first attempt I thought I was following your recommendations. I did not sieve the cay at all so there were particles up to 6mm in size. You pointed out that I had only produced the 1/1 binder not a LTGS test sample. Only now does it seem to be solidifying (it has been in a plastic food container, with a lid sealing it, on a 25-60C surface since 24th Dec). It developed a white-ish crust I think it may be caustic soda crystals reforming (if that is possible) as there was several days I looked at it and there was a liquid I could see if I turned it up slightly.

I had a second attempt on the 26th December where I mixed 6 different 'muffin tin'-sized batches of different strength binder (1/1, 1/2, 1/3, lye/clay) then mixed each of them with aggregate (more of the same sieved clay) so that the binder was either 20% of the completed mix ot 40%. I used a kitchen sieve this time so there were particles up to 2-3mm in size. I had however not taken in the point of resting the binder before mixing in the aggregate. I think these will be useless. One is still very wet, I can not get it out of the silicone mould. The other 5 are out and drying faster. The mould has been kept on the same surface as the first test (25-60C), then when removed from the silicone mould put in a metal tin on the hob over the fire box of my batch box rocket.

I have got an old honey strainer/sieve that is much finer and I should probably use that to get the binder clay (at least) finer based on your comment about the finer particles give a better insulating material.
So far with explanations and background.

How would you make a LTGS refractory out of lye & expansive/shrinking clay, using the same clay as aggregate? Please would you write it in a similar way that recipe books are written? I.e. so that someone that has done baking in the past, but has never baked a stollen for example, will be able to bake it.
I understand that all mineral deposits are different and hence the recipe may need to be in a range (like the lye/clay proportions in the binder and binder/aggregate proportions in the mix). But if you can recommend the range I will know how far to test?
Times for resting (equivalent to time for activating yeast or rising for a loaf of bread)?
When it comes to consistensies would you compare them to common household articles (tooth paste/milk/cream [there are generally 2 thicknesses of running cream due to fat content])?
What heating is required and at what points?

The more detailed/specific procedures we can get into the forum about a specific source material the more likely it is that people will use it. I know that is what Costalrocket is wanting to get together for SweetPDZ-zeolite. Here it is this expansive clay I can source cheap and easy, and if I have been able to make a LTGS out of it with your help, others that can source expansive clay in other locations can do it too.

Many thanks in advance, Esbjorn

[Deleted]

Clay particles in the size of several mm will act like holes in the mixture and make it brittle.
Try to dissolve them in a very thick slurry.

Making a binder from expansive clays is quite difficult as it is hard
to achive the required extreme concentration of lye.

Only very reactive mineral materials such as zeolite, fly ash or metakaolin
make it possible to deviate from the standard one-to-one ratio

The general recipe for making a LTGS binder:
To make a binder dry and very fine particles are required.
Mix the very fine clay with lye in a by weight ratio of one to one.
Then add a very small amount of water and mix as well as possible,
then add another very small amount of water and mix again.
repeat it until more water will not create more heat from the lye.
Continue mixing until you have got a thick smooth paste.

Using hot water and keeping the mixture hot in a water bath
will improve the result significantly.

My mixtures of bentonite with a binder made from 0-1mm zeolite
with ratios from 3/1-4/1 perform pretty well
in my cellar at temperatures between 12-15°C,
despite the extremely high water content.

[Deleted]

Launa is speculated to be derived from the Serpentine subgroup, the pyroxene group and from Sepiolite.

The chemical composition may vary a huge lot.
Launa can be composed of alumino silicates which may contain quite large amounts of other metal oxides
or of minerals mainly containing magnesia and iron.

Contrary to the alumina the magnesia can only react with acids and not with lye.
In the case of magnesia and iron a mixture of organic acids and phosphoric acid will likely work.
The LTGS principle of extreme chemical attack for a binder can be applied with acids as well.

Zeolite binders with a high mineral/lye ratio can bind rather inert minerals as well.

[esbjornaneer]

Hello Karl,
Thank you for your answers and explaination about launa.

Your instructions here are great! The point about when there is enough water was much needed. I will have a go with hot water and doing it over a pan of boiling water.
How is it difficult to get 'the extreme concentration of lye'? The amount of caustic soda is easy to weigh, it is just to add a small spray/spoonful at the time. Am I missing something? I agree that it will/may be trickier to know if more heat is generated, when adding the next drop of water, while doing it over a pan of boiling water than when doing it in a metal container with a hand feeling the base of the container. How would one get over that complication?

How much fibre would you use in this mix and when should it be added?
I assume it is the binder that go in the hot water bath. How long should it be kept in the hot water bath? Should it be stirred/mixed for the whole of that time? And is it good to mix with more of the same clay (as aggregate) at this point? Or should the binder be left for a while after the hot water bath? How long? The aggregate should be as fine as possible too, right? Should that mix be rested or is it good to use straight away?

[Deleted]

It is difficult to get 'the extreme concentration of lye' because expansive clays suck in a lot of water,
thus hinder the desired reaction with the lye.

1% to 3% fibers are sufficient.
Fibers should be added at the very end.

Yes it is the binder that should go into the water bath.
How long it has to stay there depends on the kind of clay.
Once it gets very thick more water can be added.

For high thermal insulation the aggregates should be fine as well.

If the mix should be rest depends on the clay.
You will have to make tests yourself.

[esbjornaneer]

1% to 3% fibers are sufficient.
Fibers should be added at the very end.

Fiber % is by weight? And added after the aggregate is mixed in?

It is difficult to get 'the extreme concentration of lye' because expansive clays suck in a lot of water,
thus hinder the desired reaction with the lye.

So if water gets sucked up by the clay before it dissolves the caustic soda, will the water be released from the clay again when the lye from the caustic that has dissolved reacts with the wet clay? Is that why it gets too diluted?

Yes it is the binder that should go into the water bath.
How long it has to stay there depends on the kind of clay.
Once it gets very thick more water can be added.

Is it the heat that evaporates water at this point? And what quantity of water should be added? Small amounts to keep it paste like? Or has the binder at this point completed its creation and the water added is towards mixing in the agregate?

[Deleted]

Dec 29, 2017 9:10:35 GMT -8 esbjornaneer said:

Fiber % is by weight? And added after the aggregate is mixed in?

Yes, fibers by weight and after the aggregates because the fibers will make the mixture more stiff and thus harder to mix properly.

So if water gets sucked up by the clay before it dissolves the caustic soda, will the water be released from the clay again when the lye from the caustic that has dissolved reacts with the wet clay? Is that why it gets too diluted?

Yes.

Is it the heat that evaporates water at this point? And what quantity of water should be added? Small amounts to keep it paste like? Or has the binder at this point completed its creation and the water added is towards mixing in the agregate?

The thickening is manly due to the chemical reactions,
the evaporation plays a less importand role.
For some clays or other minerals more water is required to prevent hardening.
For example zeolite binders with very high ratios of 4/1 or higher can get into an insoluble state if keept at a very concentrated level for to long.
Red clays with very high potassium content are sensitive for that too.
In general a binder should be kept as concentrated as possible until it is used.

[esbjornaneer]

In order to not get the lye too diluted: Would it be better to have some soda crystals still undissolved in the mix for a long while to make sure it does not get too much water? Or to mix the water and soda so it just dissolves before adding the clay for the binder?

We are still talking dry weight of fibre to dry weight of whole mix, right?
You have talked about kitchen/toilet paper, can other papers be used or do they have too much clay (or other crap) in them nowadays? Cardboard? What is the best way to extract the fibers from the paper?

OK. Now lets say I have got the binder together. Do I add the binder to aggregate, or aggregate to binder? Is it better to make the binder sloppy before mixing with dry clay aggregate? Or do I combine it a little at the time and adding extra water to keep it workable a little at the time too?
I mix in aggregate of the same clay: 20%-40% binder, 80%-60% aggregate (of which 1-3% are fibers)

You talked about expansive clay LTGS not being good as a pourable refractory mix. So I'll keep it spreadable, like room temp butter? Or stiff as a bread dough?  To get it into a former like one does with adobe bricks.
Should it be cured slowly? Should it be kept in a sealed bag? Should it have water misted onto it like cement based mortars/concrete has in dry environments?

Then what is the point at which I can test if it actually became a geopolymer? And how do I know that it is a geopolymer rather than just a dried clay item?

[Deleted]

Dec 30, 2017 0:05:43 GMT -8 esbjornaneer said:

In order to not get the lye too diluted: Would it be better to have some soda crystals still undissolved in the mix for a long while to make sure it does not get too much water? Or to mix the water and soda so it just dissolves before adding the clay for the binder?

The working horses of geopolymerization are not the lyes Themself but their basic salts.
Waterglass and LTGS binders are in essence basic salts.
Therefore no undissolved lye should remain

We are still talking dry weight of fibre to dry weight of whole mix, right?

I am always refering to dry matter by weight.

You have talked about kitchen/toilet paper, can other papers be used or do they have too much clay (or other crap) in them nowadays? Cardboard? What is the best way to extract the fibers from the paper?

Add paper to hot water and stirr.

OK. Now lets say I have got the binder together. Do I add the binder to aggregate, or aggregate to binder? Is it better to make the binder sloppy before mixing with dry clay aggregate? Or do I combine it a little at the time and adding extra water to keep it workable a little at the time too?
I mix in aggregate of the same clay: 20%-40% binder, 80%-60% aggregate (of which 1-3% are fibers)

Once you know how much water is required for the desired consistence mix binder and water, then give it to the dry matter.

You talked about expansive clay LTGS not being good as a pourable refractory mix. So I'll keep it spreadable, like room temp butter? Or stiff as a bread dough?  To get it into a former like one does with adobe bricks.
Should it be cured slowly? Should it be kept in a sealed bag?

You can keep it spreadable or like adobe and use a former.
Noncastable LTGS mixtures do not need sealed curing.
Just let it dry.
With forced drying capillary forces may move the salts toward the surface
and leave a lower concentration in the core.
You may cure it at elevated temperatures in dry state.

Should it have water misted onto it like cement based mortars/concrete has in dry environments?

No.

Then what is the point at which I can test if it actually became a geopolymer? And how do I know that it is a geopolymer rather than just a clay item?

Once it is dry and cured at at least 65°C or for several weeks at ambient temperatures.
Submerge samples in water for 24 hours.
If it does not fall apart it is a geopolymer.

The required minimum curing temperature depends on the clay and the amount and kind of the used binder.
For example loess loam with zeolite based binder requires curing above 100°C to get sufficiently water resistant.
With a standard LTGS binder loess loam requires significantly higher temperatures.
Other clays may cure sufficiently at ambient temperatures.

[esbjornaneer]

This is great Karl! I think I have the process clear now to go ahead with the next lot of testing.
I was thinking based on the ranges of binder/aggregate and fibre/mix you have specified that I need to make 9 samples at least:
20% binder with 1%, 2%, & 3% fibre
30% binder with 1%, 2%, & 3% fibre
40% binder with 1%, 2%, & 3% fibre
But as I will be able to make 6 samples at a time due to the muffin tin I have. Do you advice I make the gradients smaller so say 20%/27%/33% & 40% binder? Or would it be in the fibre content that you would expect to see a greater impact to the test/experiment? Or shall I just stick with the 9 samples and hone in more on it based on the results?

[Deleted]

A higher amount of samples will broaden your knowledge base.
However starting with a smaller amount and then hone in more on it based on the results is a good idea.

[esbjornaneer]

Thank you!

Should the water added to the binder just before adding to the dry aggregate be hot or cold?

Does it make any difference if the water and fibre are still hot or cold when added to the mix? I assume minimum extra water is best.

If the sample falls apart in water it is either 1 that I did not get the binder to react properly or 2 that I did not cure it for long enough/high enough temperature? How would I know which?

[Deleted]

Dec 30, 2017 7:49:09 GMT -8 esbjornaneer said:

Should the water added to the binder just before adding to the dry aggregate be hot or cold?

Chemistry usualy works better if it is warm.

Does it make any difference if the water and fibre are still hot or cold when added to the mix? I assume minimum extra water is best.

Warme water makes mixtures more plastic.
You may keep small amounts of aggregate aside so that you can adjust the consistency better.

If the sample falls apart in water it is either 1 that I did not get the binder to react properly or 2 that I did not cure it for long enough/high enough temperature? How would I know which?

Repeat the thest with a sample cured at a significantly higher temperature.
If it still fails then it is likely the binder.

I forgot to mention:
Paper fibers which are not as stiff as mineral fibers can be added to the water.

[esbjornaneer]

Thank you. But I am not understanding what you mean with this:

Dec 30, 2017 8:56:45 GMT -8 @karl said:

I forgot to mention:
Paper fibers which are not as stiff as mineral fibers can be added to the water.

[Deleted]

Paper fibers can be added much earlier.