Karls Geopolymer Experiments

[jliebler]

Mar 15, 2015 13:20:48 GMT -8 @karl said:

Vcas 160 is made from recycled glass.

A Si/Al ratio of three means a low melting point.
A F,M-PSDS matrix has a fusion temperature of about 900 degree C, according to the paper.

The genaral rule for any aluminium silicate ceramic:
The higher the alumina content the higher the melting point.

If you want to get an extremely temperature resistant
geopolymer with a melting point above 1900 degree C
use cesium hydroxide, which will also give extreme
shock resistance.
Pretty expensive though.

I'm  thinking that 78%  fine mullite grog, 10% Agsil 16H, 7% hydrated lime (about what CaO the blast furnace slag contributes to the Davidouts formulation) should make a fine dry mix with 5% water.   Basically substituting powdered potassium water-glass for the KOH in the "standard" recipe.
Using powdered water glass adds some silica and eliminates  the need to "disolve" that silica, so hopefully the geo-polymer will be mostly the higher melting temperature poly silate dysiloxo form. the remaining Mullite is good to ridiculous temperatures, about 1800C.  For a lower density more insulating material that will not see extreme temperatures, above 700C, the grog would be replaced by cenospheres or type f fly ash.

edit  It is very doubtful that the "firebox" of a batch box rocket gets to 900C.  The riser, however, is known to reach over 1200C under ideal conditions. My tentative plan is to use commercially available ceramic fiber boards rated for 1300C for the riser, but geo-polymer foam tiles are still interesting.
edit 2 Just looking at fusion temperature figure 12 says 1400C for potassium with Si/Al of 1.  But, other than density in figure 11, a rather surprisingly low 0.9gm/cc, their is almost no mention of such materials.  Also figure 18 show that a Calcium-Potasium PSS is still quite strong at 1000C.
edit 3 I guess I must reconsider the mullite Grog after reading:   www.geopolymer.org/fichiers_pdf/GEOASH.pdf    where it says to reject, as unsuitable, any fly ash with over 5% mullite.  Also, must use the blast furnace slag  (or possibly Vcas160) free lime causes "flash set".
edit 4  I miss read the paper!! The discussion, that concluded that high mullite materials were unsuitable, was referring to the user hostile methods, in fact ALL types of grog and fly ash are suitable for forming K-Ca geopolymers with the "user friendly" technique.  In fact the higher mullite starting materials lead to substantially greater compressive strength @ 28days as shown in figure 2.  But the caution about free lime is valid. 

[Deleted]

For a source of dry silica you may consider
Hr-50-NanoSilica from the manufacturer of Vcas 160
www.vitrominerals.com

[jliebler]

Well, After lots of Googling and phone calls I've found a way to obtain a small amount of slag cement AKA ground blast furnace slag and class f fly ash. I'll have to drive 3 hours each way to pick up 2 five gallon buckets of each but the price is right (free). This stuff is only sold by the carload!

[Deleted]

With respect to the Project GEOASH:
Do not let confuse you so easily.
What the paper says abut mullite is completely bogus,
even in fly ash most of it is amorphous, not chrystaline.
www.arrb.com.au/admin/file/content128/c6/12635_CT_Importance%20of%20Reactive%20in%20geopolymer%20formation.docx.pdf
Chrystaline fly ash would be completely useless for geopolymers or cement.
With respect to grog it becomes even more bogus.
It would be only true for chrystaline mullite, or any other chrystaline material.
That is why most natural silicates or alumino silicates need to be calcined.
Calcination results in an amorphous, glassy structure, which is required for any pozzolan.

It is so hard to read on the mobile device I am using at night and the link does not work,
thus I have missed it at first.

The more I look at so called "scientific papers" the more raises my contempt for "scientists" in general.
The teaching of it: Do not trust any paper to much if you have not faked it yourself .
I have two professional qualifications myself, which both are equivalent to a Bachelor.

BTW
The G-200 HP (Potash) Feldspar sold by axner contains K₂O 13.20%, Na₂O 1.52% and CaO 0.75%.
If calcined no additional lye would be required.

[jliebler]

Mar 17, 2015 9:47:21 GMT -8 @karl said:

With respect to the Project GEOASH:
Do not let confuse you so easily.
What the paper says abut mullite is completely bogus,
even in fly ash most of it is amorphous, not chrystaline.
Chrystaline fly ash would be completely useless for geopolymers or cement.
With respect to grog it becomes even more bogus.
It would be only true for chrystaline mullite, or any other chrystaline material.
That is why most natural silicates or alumino silicates need to be calcined.
Calcination results in an amorphous, glassy structure, which is required for any pozzolan.

It is so hard to read on the mobile device I am using at night and the link does not work,
thus I have missed it at first.

The more I look at so called "scientific papers" the more raises my contempt for "scientists" in general.
The teaching of it: Do not trust any paper to much if you have not faked it yourself .
I have two professional qualifications myself, which both are equivalent to a Bachelor.

BTW
The G-200 HP (Potash) Feldspar sold by axner contains K₂O 13.20%, Na₂O 1.52% and CaO 0.75%.
If calcined no additional lye would be required.

Thank you again Karl!
       The G200 would be a Very economical source of alkali metals!  It says it melts between 1100c and 1300c.  How would one calcine it?

[Deleted]

It could be calcined at 650°C-750°C like metakaolin or more grog like at about 1000°C.
Mechanical activation with a ball mill could also be done.

[jliebler]

 Thank you Karl!
I'm likely to visit Laguna clay, a company acquired by Axner and close to where I live, in the next few days, I'll see what it takes to have them calcine some K200.  I have collected the parts for my ball mill, I have 3 jar sizes I can use, 1 quart, 1/2 gallon and 1 gallon.

For those interested in "green building" geo-polymer concrete, consisting of 90% recycled material ( fly ash & ground granulated blast furnace slag) and 10% alkaline activator made by a low energy use processing of abundant minerals can replace ALL Portland cement in ALL applications, generating Substantially reduced GWP, with significantly improved levels of thermal resistance (better than wood), longevity and strength.

[Deleted]

Calciners have usually capacities of several tons to be economical.
Likely some companies offer calcined potash feldspar, maybe as calcined orthoclase.

[jliebler]

I'm became interested in fly ash geopolymers as an alternative to Portland cement concrete after I came across this: www.cipremier.com/e107_files/downloads/Papers/100/36/100036036.pdf
Unfortunately it is about a user hostile formulation. This paper is the only place I've found any data on thermal conductivity and one of his mixes was only 0.05w/k while it had the strength of weak concrete, almost strong enough for "structural" applications. That is half the conductivity of 8 -1 perlite concrete which has less than 1/15 the compressive strength and is all but useless. There is simply no data on the thermal conductivity of the Davidovitz proposed "standard" geopolymer cement using class f fly ash, GGBFS and user friendly KSil. I'm thinking how can I do a thermal conductivity test myself with some degree of accuracy. Here is the plan so far: Cast a rather large area relatively thin "tile" of the sample material say 20cm. x 20cm. x 1 cm. & cure it. I have an electric "hotplate" of that size (edit it's actually 30cm. x30cm. ) and a "kill-0-watt" and a variac to heat the lower surface back to room temperature while measuring the energy needed, while a pot full of ice water sits on the top surface. The one item I don't have but will need to "acquire" is an accurate and precise temperature & temperature difference measuring thermometer (available from Amazon for under $20).
.

[Deleted]

Fly ash and slag have relatively low thermal conductivities by nature.
Fly ash due to its hollow spherical structure and additionaly both due
to relatively high amounts of different chemical elements.
Ashes from plants, as used in the paper, contain many different chemical elements too.
Also the paper uses relatively high amounts of water.

If one uses water glass the thermal conductivity can be lowered
by simply combining it with a different lye, thus raising the amount
of different chemical elements in the geopolymer.

[jliebler]

Thank you yet again Karl!
Somewhere I read that K Ca geopolymers had lower conductivity than Na Ca. You are suggesting that using both Na and K could lower conductivity even further. I'll add that to my list of experiments. Getting the thermal conductivity below 0.04 would surpass very expensive Foamglass which only has 1/2 the compressive strength of wood. The thermal conductivity of wood is about 0.144 or about twice the conductivity of the worst reported in the paper. Foamed concrete (using magnesium cement) is occasionally used as cavity fill insulation, its conductivity is 0.05 but it is quite pricey and crumbles when strained.

[Deleted]

KOH and NaOH can complement each other.
Likely there is a combination of KOH and NaOH,
which will result in better dissolution and form a stronger network
as each of them alone.

Some scientists came to the same conclusion in the summary of
"Effect of Alkali Choice on Geopolymer Properties".
onlinelibrary.wiley.com/doi/10.1002/9780470291191.ch16/summary

[Deleted]

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

[pyrophile]

Hi everybody!
Did somebody allready attend to Geopoymers camp of Davidovits?

On Geopolymer Institue's site, ther is this coference of Davidovits :"Why Alkali-Activated Materials are NOT Geopolymers ?" but it is too difficult for me!
www.geopolymer.org/faq/alkali-activated-materials-geopolymers

[Deleted]

Carbonation tests can indicate excess/lack alkali.
Important for steel reinforced concrete.
www.understanding-cement.com/carbonation.html
www.understanding-cement.com/deleterious.html