Geopolymer For Low-Tech Tinkerer
Jun 11, 2015 7:11:31 GMT -8
pinhead, morticcio, and 1 more like this
Post by Deleted on Jun 11, 2015 7:11:31 GMT -8
Please ask any questions in my "Karls Geopolymer Experiments" thread,
which is already very cluttered.
Could someone make this read only please ?
Donkey said I should write a book for the low-tech geopolymer tinkerer.
However there is not enough to say to fill a book.
As requested something light but informative and easy to follow.
Davidovits defines as user friendly:
Slurry soluble
silicate/kaolin
1.25<SiO2/Na2O>1.45
For NaOH this would be
0.625<SiO2/NaOH>0.725
Any soluble silicate
SiO2/Na2O > 1.45
For NaOH this would be
SiO2/NaOH>0.725 or by weight > (60*0.725)/40 ~ >1.01/1
This definition allows surprisingly high amounts of NaOH in mixtures.
Eg. commercially available water glass for pottery has:
SiO2/Na2O ~ 3.4
SiO2/NaOH ~ 1.7 or by weight (60*1.7)/40 ~ 2.55.
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.
The "just add water" mixture may become quite hot, if water is added.
Add water until you get consistency like cream, then fill it with coarse aggregates.
Porous aggregates like scoria, porous grog, perlite or vermiculite are preferable,
as they will support drying and firing.
Sand could be used instead.
Small amounts of organic matter like sawdust can be added too.
In water solutions calcium hydroxide can take away the carbon from carbonates of alkali metals such as
Lithium, Sodium, Potassium, leaving them as their hydroxide.
Ca(OH)2 + Li2CO3 → CaCO3 + 2 LiOH.
Ca(OH)2 + Na2CO3 → CaCO3 + 2 NaOH
Ca(OH)2 + K2CO3 → CaCO3 + 2 KOH.
Thus in mixtures with lime or cement the hydroxides of alkali metals can be replaced
by their more user friendly carbonates for alkaline activation.
With the help of water glass one can virtualy turn dirt into a castable refractory.
For home made water glass mixt 550g silica gel (powderized for better dissolution),
450 NaOH and two liter water.
Take a part of the water and add slowly silica gel and NaOH, add more water if needed.
When the mixture cools down it can be heated for a quick dissolution.
If all is dissolved add the rest of the water.
With only one liter the resulting geopolymer will harden faster and become denser and harder,
but more expensive.
To get the same amount of lye molecules for potassium it would be:
550g silica gel, 630 KOH and two liter water.
Thermally expanded perlite and vermiculite are calcined pozzolans,
widely available for relatively small money.
Due to their relative softness they can be easily pulverized to increase reactivity
eg, by shaking in a container with hard balls.
Thermally expanded clay is another widely available calcined pozzolan,
but harder to mill.
For a binder with water glass:
45% pulverized perlite or vermiculite, 45% natural clay and 10% lime.
Add water glass until you get consistency like cream, then fill it with coarse aggregates,
or just thicken it with more clay.
Porous aggregates like scoria, porous grog, perlite or vermiculite are preferable,
as they will support drying and firing.
Sand could be used instead.
Small amounts of organic matter like sawdust can be added too.
For mixtures with ingredients of very different densities quicklime should be used
to ensure short pot times to prevent segregation.
Your clay soil may require slightly different percentages.
You should always make some tests with small amounts.
I have tested water glass, pozzolan, clay and lime mixtures with
metakaolin, fly ash, perlite and grog, with kaolin, ball clay and ordinary white clay.
Commercial waterglass will need some additional lye.
As the polymer in the name suggests are geopolymers the inorganic equivalent of resins such as polyester or epoxy.
All techniques for resins can also be used for geopolymers,
besides casting also composite laminates or other layered shells
to realize even very complicated forms in a simple way.
For example make the form for a PvdB batch box out of cardboard.
Protect the cardboard against water then add layers of geopolymer by brushing, spraying or other means.
The wet layers can be sprinkled with coarse aggregates like sand or reinforced with refractory fibers.
Or saturate mineral tissue or mineral blanket with geopolymer and wrap it around the form like the doctor does with a plaster bandage.
The final thickness of such a geopolymer shell may vary from a few millimeters to a few inches.
Note: If protected from oxigen then carbon fibers too are suitable for refractory use.
which is already very cluttered.
Could someone make this read only please ?
Donkey said I should write a book for the low-tech geopolymer tinkerer.
However there is not enough to say to fill a book.
As requested something light but informative and easy to follow.
Davidovits defines as user friendly:
Slurry soluble
silicate/kaolin
1.25<SiO2/Na2O>1.45
For NaOH this would be
0.625<SiO2/NaOH>0.725
Any soluble silicate
SiO2/Na2O > 1.45
For NaOH this would be
SiO2/NaOH>0.725 or by weight > (60*0.725)/40 ~ >1.01/1
This definition allows surprisingly high amounts of NaOH in mixtures.
Eg. commercially available water glass for pottery has:
SiO2/Na2O ~ 3.4
SiO2/NaOH ~ 1.7 or by weight (60*1.7)/40 ~ 2.55.
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.
The "just add water" mixture may become quite hot, if water is added.
Add water until you get consistency like cream, then fill it with coarse aggregates.
Porous aggregates like scoria, porous grog, perlite or vermiculite are preferable,
as they will support drying and firing.
Sand could be used instead.
Small amounts of organic matter like sawdust can be added too.
In water solutions calcium hydroxide can take away the carbon from carbonates of alkali metals such as
Lithium, Sodium, Potassium, leaving them as their hydroxide.
Ca(OH)2 + Li2CO3 → CaCO3 + 2 LiOH.
Ca(OH)2 + Na2CO3 → CaCO3 + 2 NaOH
Ca(OH)2 + K2CO3 → CaCO3 + 2 KOH.
Thus in mixtures with lime or cement the hydroxides of alkali metals can be replaced
by their more user friendly carbonates for alkaline activation.
With the help of water glass one can virtualy turn dirt into a castable refractory.
For home made water glass mixt 550g silica gel (powderized for better dissolution),
450 NaOH and two liter water.
Take a part of the water and add slowly silica gel and NaOH, add more water if needed.
When the mixture cools down it can be heated for a quick dissolution.
If all is dissolved add the rest of the water.
With only one liter the resulting geopolymer will harden faster and become denser and harder,
but more expensive.
To get the same amount of lye molecules for potassium it would be:
550g silica gel, 630 KOH and two liter water.
Thermally expanded perlite and vermiculite are calcined pozzolans,
widely available for relatively small money.
Due to their relative softness they can be easily pulverized to increase reactivity
eg, by shaking in a container with hard balls.
Thermally expanded clay is another widely available calcined pozzolan,
but harder to mill.
For a binder with water glass:
45% pulverized perlite or vermiculite, 45% natural clay and 10% lime.
Add water glass until you get consistency like cream, then fill it with coarse aggregates,
or just thicken it with more clay.
Porous aggregates like scoria, porous grog, perlite or vermiculite are preferable,
as they will support drying and firing.
Sand could be used instead.
Small amounts of organic matter like sawdust can be added too.
For mixtures with ingredients of very different densities quicklime should be used
to ensure short pot times to prevent segregation.
Your clay soil may require slightly different percentages.
You should always make some tests with small amounts.
I have tested water glass, pozzolan, clay and lime mixtures with
metakaolin, fly ash, perlite and grog, with kaolin, ball clay and ordinary white clay.
Commercial waterglass will need some additional lye.
As the polymer in the name suggests are geopolymers the inorganic equivalent of resins such as polyester or epoxy.
All techniques for resins can also be used for geopolymers,
besides casting also composite laminates or other layered shells
to realize even very complicated forms in a simple way.
For example make the form for a PvdB batch box out of cardboard.
Protect the cardboard against water then add layers of geopolymer by brushing, spraying or other means.
The wet layers can be sprinkled with coarse aggregates like sand or reinforced with refractory fibers.
Or saturate mineral tissue or mineral blanket with geopolymer and wrap it around the form like the doctor does with a plaster bandage.
The final thickness of such a geopolymer shell may vary from a few millimeters to a few inches.
Note: If protected from oxigen then carbon fibers too are suitable for refractory use.