Karls Geopolymer Experiments

[andyd]

Hello, Karl! Thank you for your explanation, as for self-made water glass I know that this quite dangerous process and want to make less dangerous way: get normal water glass on the market with MR=3...3,3 and lower molar ratio by adding certain amount of NaOH (flakes).I hope this method will be OK.

As for calculation of Si:AL ratio... It's not clear why when Si:Al=1 you need to multiple molar mass of SiO2 by 2 (2xSiO2)? And when Si:Al=2 you need to multiple SiO2 molar mass by 4. I don't understand the correlation between it, for instance if you have Si:Al = 2,5 or 4?

The next issue I have problem with ( I am sorry, but I am not a chemist and this is why asking maybe simple questions, but for me this is the only chance) calculation of Si:Al ration of one particular recipe for instance.

Let's say we have fly-ash (SiO2=58,23%; Al2O3=25,3%), GGBS (SiO2=39,6%; Al2O3=10,4%) and we also have water glass with molar ratio of 1,5 and density 1,4958 g/cm3 (SiO2=23,98%; Na2O=16,5%).

We have a base recipe: 50% of sand, 25% of GGBS and 25% of fly-ash. We also add our water glass over this amount of 20%.

1. We calculate the SiO2 provided by fly-ash: 58,23% x 0,25 = 14,56%
We calculate SiO2 provided by GGBS: 39,6% x 0,25 = 9,9%
And SiO2, provided by water glass: 23,98% x 0,20 = 4,796% and as we have the density of water glass of approximately 1,5 we divide it by 2 and get 2,39% of SiO2 provided by water glass.
Then we summ up the overall amount of SiO2 in our recipe and get 26,85%.

2. We calculate the Al2O2 provided by fly-ash: 25,3% x 0,25 = 6,325%
Al2O3, provided by GGBS: 10,4%x0,25=2,6%
We summ up the amounts of Al2O3 and get 8,925%.

3. If we simply divide these results we will get: SiO2:Al2O3=26,85%/8,925%=3,0

4. If I will follow your explanation, I will get molar mass of SiO2 (60,08439 g/mol) and multiply the result obtained in (1) For SiO2: 60,08439x26,85%=16,133 g/mol - the amount of SiO2 atoms in our recipe. Then I will calculate the atomic mass of Si, considering that Si=46,74347% and O=53,25653%: 16,133x0,4674347=7,54 g/mol - molar mass of Si atoms in our recipe.

5. We do the same for Al2O3: molar mass is 101,96136 g/mol, multiple by 8,925%: 101,96136x8,925%=9,1 g/mol. And if Al=52,92503% and O=47,07498%, we come to the result: 9,1x0,5292503=4,82 g/mol - molar mass of Al atoms in the recipe.

6. We obtain Si:Al ratio: 7,54/4,82=1,564

Am I right in my calculations or there is a mistake somewhere made? I would be grateful for your help.

[Deleted]

Adding lye to liquid waterglass is a common aproach.
You can also get sodium silicate as a dry powder eg. Red Devil Tsp/90 cleaner,
other Phosphate-Free TSP Substitute Cleaner, or formsil 113 by pottery supply.
www.reddevil.com/sku-docs/sds-0261-0265.pdf
cds.a9t2h4q7.hwcdn.net/main/items/media/SUNNY001/Prod_Tech_Spec/641ProductDataSheet.pdf
www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dhpc&field-keywords=TSP+Substitute+Cleaner
For other sources look for sodium metasilicate nonahydrate or disodium trioxosilicate nonahydrate.
Sodium silicate powder can be used for just add water mixtures to avoid handling of dangerous caustic liquids.

The chemical formula Al2O3 of aluminium oxide tells you that it contains two atoms of aluminium.
As silica with the formula SiO2 contains only one silicon atom you have to multyply it by two for a 1/1 ratio
and by four to get a 2/1 ratio of Si/Al.

[Deleted]

andyd what do you want to achieve and where are you located ?

If you do not want to trim a formula to set new records with specific properties exact ratios are not very important.

For practical use all you need to know you can find here:
Geopolymer For Low-Tech Tinkerer.
donkey32.proboards.com/thread/1701/geopolymer-low-tech-tinkerer

[andyd]

Hello Karl!

I'm from Russia. I just want to understand what Davidovits say in terms of application of geopolymers and try to make different recipes with Si:Al = 1; 2; 3; 20. Also, I am looking for a cheap recipe of geopolymer concrete as well as not cheap but with hight properties such as fire-resistance, heat resistance etc. If you don't understand the materials, it's properties - you will never get the desired results.

The other problem I have is eflorescence on the surface of ready geopolymer concrete. And I don't really understand where it comes from? Of course I do understand that it comes from water glass, namely NaOH in it. And it might be overdosage of NaOH in my recipe that is why "free" NaOH comes onto the surface. And also, as Davidovits say it might happen when you mix all powders together without respect an order of mixing (but I am not!) And you get alkali-activated material, not geopolymer. So this is the second thing I want to understand.

As for my calculations of Si:Al ratio, am I right or not? Shall I follow this way to check up my recipes?

[Deleted]

The definition of Geopolymer once given by Davidovits can only be fulfilled with pure calcined kaolin,
anything else would by this definition just be alkali-activated material, not geopolymer.

You can reduce eflorescence by sealing it in a plastic bag for 28 days
or cure at elevated temperatures under humid conditions or sealed in the bag..

Potassium hydroxide causes much less problems with eflorescence.
While it is more expensive than NaOH it may be cheaper in use
as it does not thicken metakaolin or other clays as much,
and thus requires much less liquid.
Potassium geopolymers have generaly a higher melting point than sodium geopolymers.

You can use the Molar Mass and Mass Percent Composition Calculator to get the precise numbers for any chemical formula.
www.caymanchem.com/chemAssistant/Tool/4002
Then do the simple math.

See also:
Geopolymer analogs of high-temperature minerals.
donkey32.proboards.com/thread/1620/geopolymer-analogs-high-temperature-minerals

If you want a source of cheap reactive kaolin use solventless mechanochemistry with a ball mill.
Of course you could also use a ball mill to powderize bricks or other ceramic material or even
natural vulcanic stone like Basalt.

You can even mill the material together with NaOH or KOH to create the waterglass
by solventless mechanochemistry and get a just add water mixture.
Caution: Do not breathe this dust.

Mechanochemical treatment of Serbian kaolin clay to obtain a highly reactive pozzolana.
www.doiserbia.nb.rs/img/doi/0352-5139/2013/0352-51391200107M.pdf

Effects of mechanical and thermal activation on pozzolanic activity of kaolin containing mica.
www.researchgate.net/profile/Biljana_Ilic/publication/293017733_Effects_of_mechanical_and_thermal_activation_on_pozzolanic_activity_of_kaolin_containing_mica/links/56e11ac008ae9b93f79c43d8.pdf

Preparation of pozzolanic addition by mechanical treatment of kaolin clay.
www.researchgate.net/profile/Aleksandra_Mitrovic5/publication/265909076_Preparation_of_pozzolanic_addition_by_mechanical_treatment_of_kaolin_clay/links/551a9a160cf244e9a458a1b2.pdf

homemade ball mill
www.youtube.com/results?q=homemade+ball+mill

[andyd]

Not only metakaolin, kaoline (kaolinite mineral) based materials according to Davidovits are geopolymers. He also speaks about Fly-Ash, GGBS and Rock based geopolymers, so one can use any material which is contain amorphous Si and Al. The main difference is the way you mix. He always say that first you must prepare a binder to proceed different reactions: dissolution, coordination, depolymerisation etc. So, he advised to mix binders (FA, GGBS, MK etc.) with soluble silicate solution (water glass) Na- or K- based. Only after geopolymer reaction occurs you should add your aggregates. 

As for sealing and curing geopolymers in order to reduce efflorescence, yes this is quite effective way, but imagine you build a house with pourable concrete (not pre-cast) on site and it's not possible to cover it with bag and wait 28 days, as well as to cure it at hight temperatures. 

Davidovits say that if you follow the right steps of mixing, if you will get the right molar ratio for water glass and your proportions of the binder materials will be good, you will not face the efflorescence effect. 

This is why I want to understand the chemical composition and Si:Al ratio in my recipes.

[Deleted]

Basically the composition of a geopolymer needs to fulfill
the composition of natural minerals or of a mixture thereof
with finely devided components to ensure complete chemical reactions
without unreacted components.

You can find chemical formulas for minerals here:
webmineral.com/help/Composition.shtml

For example general composition of plagioclase.
(Na,Ca)(Si,Al)4O8
Molecular Weight = 270.77 gm
Sodium 4.25 % Na 5.72 % Na2O
Calcium 7.40 % Ca 10.36 % CaO
Aluminum 9.96 % Al 18.83 % Al2O3
Silicon 31.12 % Si 66.57 % SiO2
Oxygen 47.27 % O
           100.00 % 101.48 % = TOTAL OXIDE

To get the percentage for NaOH divide it by 1.55 (Na2O 62/ NaOH 40) and multiply it with two as NaOH has only one sodium atom.
5.72 %/1.55x2 = 7.4 % of 270.77 .
It does not matter that the total percentage will be about 103.2%

Davidovits says :
“ ... the 27 Al NMR spectra of the product must exhibit a peak only at about 55 ppm
 Al may be present in the product structure only and exclusively in the coordination 4...
If it is not so, the product may not be called a geopolymer but only an alkali-activated material ...”

This very strictly formulated definition satisfies essentially only
the materials obtained by alkali activation of pure metakaolin.
www.geopolymery.eu/aitom/upload/documents/publikace/2007/2007_praha_skvara.pdf

[andyd]

Not only IV coordination should be present, also there might be (and almost is the VI coordination of aluminum). And in his book, Davodovits classifies different types of geopolymers: MK-based, fly-ash based, GGBS and fly-ash based etc. www.geopolymer.org/shop/product/geopolymer-chemistry-applications/

Indeed Davodovits at first discovered geopolymers based on metakaolin in terms of his research of inorganic binders for fire proofing (Si:Al > 20)

We are speaking about geopolymers for cement application, with Si:Al = 1, 2, 3 (according to his classification).

And my concern is how to check what Si:Al ratio we have in our recipe. Can you check my calculations please and tell me where I am mistaken?

[Deleted]

I have told you how to do the calculation, just do it in that way.

Anyway:

Si:Al = (SiO2 60) 26,85%/(Al2O3 102) 8,925% = (26,85%/60/2)/(8,925%/102) ~ 0.22375/0.0875 ~ 2.55/1.
simplified to 26.85%/8.925%/120x102 ~ 2.55/1.

Si:Al = (SiO2 60) 54%)/(Al2O3 102) 46% = (54%/60/2)/(46%/102) ~ 0.45/0.45 ~ 1/1.
simplified to 54%/46%/120x102 ~ 1/1.

[dustinmattison]

@karl what do you make/build with geopolymers? For example, instead of using earth in earth bag domes can you use geopolymers? What is the advantage? It seems like it would cost more and take more effort.

Dustin

[Deleted]

The result of a geopolymeric reaction is a natural stone.
Geopolymers are refractory.
By mixing soil with geopolymers one can create something able to breathe
like earthen walls, but also can resist rain.
One can build something that can withstand millennia and earthquakes.

[lawry]

Jun 11, 2015 7:11:31 GMT -8 @karl said:

The simplest and safest way to make a geopolymer binder is a "just add water"
powder mixture of
80% grog 200 mesh, 10% NaOH and 10% lime.
To get the same amount of lye molecules for potassium it would be
76% grog, 14% KOH and 10% lime.

Karl/anyone please assist....
The lime you mention above, is it hydrated lime?
What particle size is the vermiculite/perlite above?

Jun 11, 2015 7:11:31 GMT -8 @karl said:

For home made water glass mixt 550g silica gel (powderized for better dissolution),
450 NaOH and two liter water.

550g silica gel, 630 KOH and two liter water.

For a binder with water glass:
45% pulverized perlite or vermiculite, 45% natural clay and 10% lime.

What particle size is the pulverized vermiculite/perlite mentioned above?
Is the water mentioned here demineralized?

[Deleted]

For the just add water mixtures with fine grog I prefer quicklime,
as the heat of hydration will boost the chemical reactions
and ensures hardening at ambient temperatures.
Hydrated lime works too, but much slower.

In mixtures with water glass quicklime may cause an extremely short potlife
and thus should be added at last.

Fast and complete chemical reactions require finely devided particles,
the finer the better.

I use plain tap water.

[lawry]

Ok. Noted. Ta.
Here is a picture with what i have access to. In the middle its salt just for comparison. Perlite (right) looks "fine". Or does it still need to be pulverized more?

[Deleted]

It should be as fine as flour.