Some time back I took a bit of a look at what are being called Geopolymers. Liquid stone mixes. New kinds of cement.
Even noted in passing some other “odd bits” related to it.
All of which implies that a silicate sand, treated with highly alkaline solution, ought to form some soluble silicon compounds; then ‘polymerize’ some silicate back between the sand grains when allowed to dry and neutralize the pH.
Well, some times, some ‘muses’ rest a long time between efforts to move them another step down the road. I’ve been thinking of making an attempt at Liquid Stone all on my own for some time now. At least a couple of years. So about a week ago I started to plot. What materials? Which approach? But then decided another bit of ‘prior art’ research ought to be done. Just in case things had moved forward any, or something I’d missed might show up. Good thing, too. A lot did show up.
But first, a digression on shopping.
I spend several hours on the weekend trying to buy:
A) Strong Base. Lye (NaOH), or even KOH. Lime – CaO or hydrated lime Ca(OH)2 or heck, even Natron – aka Sodium Carbonate Na2CO3
B) Kaolin Clay. Mostly an Aluminum Silicate clay of fairly pure sort.
C) Pure Silicate – some SiO2 based stuff.
The idea being to do “mix and match” on the various stuffs and find out what worked and what was not so good.
Well, seems that the days of my youth when I could regularly buy most of that stuff at the grocery store and hardware store in my little farm town are now far gone. Lowes had “Lime”, but reading the package showed it to be some kind of “Garden Lime” bastard mix of CaO, MgO, CaCO3, MgCO3, and a few other things (some hydrated lime and some other hydrates). Basically, half (assed?) roasted dolomite / limestone. Not lime at all, really. Similarly, lye is essentially gone. There was some Drano, with a load of other stuff in the mix too. Clay? Not on your life. So it goes.
After pondering how many specialty shops and what kind of flags would go up trying to order lye on the internet… I went home to sulk. Pondering a bit more, I started looking for more papers. That’s when I found most of the stuff I’m going to link here.
But today is another day. Some small chips started to fall into place.
First off, I picked up an (expensive) bag of Diatomaceous Earth. It claims 85% Silicate. No idea what the other 15% will be. Then again, the Ancients seemed to work with whatever natural dirt was laying around, so maybe a bit of unknown crap isn’t all that important. Then I stumbled on an article complaining about clumping cat litter and how it was Bentonite Clay. Not quite the Kaolinite most of the research papers talked about, but still, it ought to work OK. At least, if my understanding of what happens is right.
No I’ve not bought the cat litter yet… but I do have a nice bag of diatomaceous earth.
So the basic “recipe” is an alkali of some sort as a catalyst, some clay with Aluminum and Silicate in it (and I hypothesize that most any other metal ions ought to be OK too, so clay with Fe or Mg content ought to work. It came from feldspars or feldspathoid minerals in the first place, so it ought to be willing to return to them…)
Then another paper gave some actual pH values. Looks like many different alkaline / basic materials might “work”. Not just lye, but things like bleach and roasted bicarbonate of soda too. (Roasting bicarb of soda turns it into sodium carbonate. That Natron referenced above. I did this when I was about 10 years old, but had hoped to just buy the stuff.) I can also try some of the drain cleaning liquids, if any of the hydroxide types are still around. Oh, and a web search showed Tractor Supply to have 50 lb bags of hydrated lime for about $3 too; so a car trip can ‘bag’ a bag.
Next weekend I’m planning to pick up the hydrated lime, some drain opener, a box of “washing soda” (sodium carbonate) or maybe a big box of bicarb if I need to roast my own, and maybe even some of that “garden lime” that isn’t quite lime… A stop at the grocery will get me some bentonite clay (that promises to ‘clump’ if I pee on it). All in all, that ought to be enough for a good start. If I see any promising quartz sand, I’ll likely get a bit of it, too.
At that point I figure I have enough “options” to find at least one “mix” that sets up.
Then tonight I did some more paper chase. Found a very nice paper from India where some guys did basically that very thing. Not as many variations on the catalytic base. (One guesses that lye is still used and available in India. Odd to think that folks in India are less constrained and have more awareness of what to do with materials than folks here in the USA… At any rate, they use lye NaOH for the alkaline basic catalyst.) More importantly, they do a very nice matrix of Bentonite clay (it being cheaper and more available than Kaolin one presumes) with various mixes of fly ash and Silica Fume that is basically a waste product from making raw silicon for semiconductors and metallurgy. I can likely use diatomaceous earth as a substitute for silica fume (both mostly SiO2 very finely divided) and maybe some of that “garden lime” in place of their fly ash and / or cement components. Finally, my varieties of base in place of NaOH. Heck, as aluminum gets used in making feldspars, I could likely even use the Drano that has bits of aluminum in it.
The paper in question is here:
Nice “meat and potatoes” research paper. State the goal ( making strong bricks that they call cubes, with geopolymer instead of traditional cement ) state the materials to try, try all the combinations, document the strength, time to set, etc. Graph and write it all up. Nicely done and likely has saved me a few weekends. I now know what has a shot at working best.
NOVEMBER 2012 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2012 Asian Research Publishing Network (ARPN). All rights reserved.
STRENGTH PROPERTIES OF GEOPOLYMER MORTAR CONTAINING
BINARY AND TERNARY BLENDS OF BENTONITE
K. Srinivasan and A. Sivakumar
Structural Engineering Division, VIT University, Vellore, Tamil Nadu, India
Geopolymer based cementitious binder is one of the recent findings in the emerging concrete technology. The
present study investigates the setting and strength properties of geopolymer mixtures containing binary combinations of
bentonite-flyash, bentonite-cement, bentonite-silica-fume and ternary blends of bentonite-flyash-lime. The effect of lime
and alkali activator (sodium hydroxide) on the geopolymerisation of bentonite was studied systematically. The
experimental results showed that the initial and final setting time of binary mixtures containing bentonite and silica fume
(5%) with alkali activator (NaOH) showed early setting time of 30 minutes compared to other geopolymer mixtures. It was
also noted that compressive strength of ternary mixtures containing 40% bentonite, 30% flyash and 30% lime (M16)
attained the maximum strength of 24.74 MPa at 28 days. The highest rate of strength gain was observed at early curing
period (7 days) for the ternary mixtures (M14) consisting of 80% bentonite, 10% flyash and 10% lime compared to other
mixtures. It can be realized from the experimental study that, geopolymerisation reaction was effective for the specimens
cured at 100°C hot air oven.
Keywords: bentonite, fly ash, silica fume, geopolymer, cement, lime, alkali activators.
AND, the whole paper is there, not just some lame abstract and a demand for $40 to get into the peep show and see if you have been ‘had’ or not…
So now I’m pretty darned sure that some kitty litter with a 5-10% diatomaceous earth and 5-10% “garden lime” when mixed with some added drain cleaner or hydrated lime has a pretty good chance of turning into something about like cement.
There are some other papers also worth reading. Each one with some different points of view. But that one has a down to earth practical bent to it that I found refreshing. No lab grade kaolin for these guys, and no fancy additives. Just things like fly ash that are very cheap waste products. The ideal stuff to turn into a resource. Dirt and chimney sweepings, mixed with some lye; and presto! Very strong usable bricks. Nice. Very nice.
One of the papers indicates that a pH of about 10 or so is enough to catalyze things. Here’s a nice pH scale with some common things on it:
The implication here being that for some class of geopolymerizing reactions, things like ammonia water might even be enough, or oven cleaner, or bleach. (though not ammonia and bleach together as that releases chlorine gas).
The other papers:
It basically finds that you can use fly ash to make something stronger than (or strong as) regular cement via an alkali catalyzed geopolymer process with pH 12 or so. It is one of those PDFs that doesn’t want to let you cut / past bits and I’m feeling a bit rushed so not going to bother breaking their “copy protection”. (Screen cap would do it, but it’s late…) They get some 150 MPa (or about 21,000 psi) strength mixes. Most cement is about 5 MPa to 30 MPa. Has a nice bibliography too.
They, too, have nice graphs and help point you toward what works and what doesn’t. Czech folks and source, so I’d trust it. Those folks generally have their head on straight.
Some folks from Down Under. Short and nice introduction.
The Geopolymerization Process
Geopolymers are a class of inorganic polymer formed by the reaction between an alkaline solution and an aluminosilicate source or feedstock. The hardened material has an amorphous 3-dimensional structure similar to that of an aluminosilicate glass. However unlike a glass these materials are formed at low temperature and as a result can incorporate an aggregate skeleton and a reinforcing system if required, during the forming process.
The reactants are an alkali metal hydroxide/silicate solution (often referred to as the chemical activator) and an aluminosilicate fine binder (typically with a median particle size in the range 1 micron to 30 microns). The binder or feedstock needs to have a significant proportion of the silicon and aluminium ions held in amorphous phases.
The most common activator is a mixture of water, sodium hydroxide and sodium silicate but other alkali metal systems or mixtures of different alkalis can be used, as can any waste source of concentrated alkali. The solution needs to be concentrated or the end product will be a crystalline zeolite rather than a geopolymer.
Commonly used binders include class F flyash, ground granulated slags or metakaolin, but any fine amorphous aluminosilicate material can be used.
As with conventional organic polymerization, the process involves forming monomers in solution then thermally triggering them to polymerize to form a solid polymer.
The geopolymerization process involves three separate but inter-related stages.
During initial mixing the alkaline solution DISSOLVES silicon and aluminium ions from the amorphous phases of the feedstock. The binder is the primary feedstock but any amorphous phases in the aggregate skeleton (stone or sand particles) will also react during this stage.
In the sol so formed, neighbouring silicon or aluminium hydroxide molecules then undergo a CONDENSATION reaction where adjacent hydroxyl ions from these near neighbours condense to form an oxygen bond linking the molecules, and a free molecule of water; OH- + OH- -> O2- + H2O
(Ref : Hench L L, “Sol-Gel Silica. Properties, Processing and Technology Transfer”, Noyes Publications, 1998)
The “monomers” so formed in solution can be represented in 2-dimensions by;-
– Si – O – Al – O – (poly[silalate]),
or, – Si – O – Al – O – Si – O – (poly[silalate-siloxi]),
where each oxygen bond, formed as a result of a condensation reaction, bonds the neighbouring Si or Al tetrahedra.
The application of mild heat (typically ambient or up to 90 degrees C) causes these “monomers” and other silicon and aluminium hydroxide molecules to POLY-CONDENSE or polymerize, to form rigid chains or nets of oxygen bonded tetrahedra.
Higher “curing” temperatures produce stronger geopolymers. As each hydroxyl ion in the tetrahedral is capable of condensing with one from a neighbouring molecule it is theoretically possible for any one silicon ion to be bonded via an oxygen bond to 4 neighbouring silicon or aluminium ions, so forming a very rigid polymer network. Aluminium ions in such a network require an associated alkali metal ion (usually Na) for charge balance.
The resultant products are;-
a rigid chain or net of geopolymer
a pore solution composed of water (from the catalytic water initially incorporated in the mix recipe plus water generated as a result of the condensation reactions), excess alkali metal ions and unreacted silicon hydroxide. In the case of sodium based activators this pore solution can be considered as a weak solution of sodium metasilicate, with a pH of about 12. It forms a continuous nano or meso porosity throughout the geopolymer unless removed during poly-condensation.
The physical properties of the hardened geopolymer are influenced by the Si/Al ratio of the geopolymer network. Below a Si/Al ratio of 3:1, the resultant 3D nets are rigid, suitable as a concrete, cement or waste encapsulating medium. As the Si/Al ratio increases above 3, the resultant geopolymer becomes less rigid and more flexible or “polymer-like”. With higher Si/Al ratios, up to 35:1, the resultant crosslinked 2D chains are more suited as an adhesive or sealant, or as an impregnating resin for forming fibre mat composites.
What looks like an interesting discussion board.
Pradeep Rana · Group of Institutions, GUNUPUR
It depends on type of Fly ash you are using, but mostly, 7.5-13.4 (Na2O) : 25-29.6 (SiO2) in sodium silicate is recommended.
Aug 1, 2013
Sanjay Kumar · Council of Scientific and Industrial Research (CSIR), New Delhi
In our understanding, only amorphous fraction of fly ash participates in reaction during early geopolymerisation and remaining acts as an aggregate. If there are free alkali available then the crystalline part participate in reaction which is very slow. Thus deciding a geopolymerisation reaction based on total Al2O3 and SiO2 is misleading sometimes.
Aug 2, 2013
Radhakrishna Krishna · Rashtreeya Vidyalaya College of Engineering
0.35 – 0.4 is the best ratio
A couple of papers give a H/T to Davidovits, then an homage to someone they say figured this out in 1950. A Mr. Chelokovski. Doing a web search doesn’t turn up much on him, so I figure it will need a native language search (or a better transliteration into what is used by more of the English language papers). An interesting “Dig Here!”. Generally, I think this process has been turned up from time to time throughout history. Build a wood fire on a clay riverbank. You get lye over clay. Water it out… maybe someone noticed the ground get hard… Also they were from Iran, so likely closer to the Russian work (and maybe using a variant spelling).
From the “Overkill On The Computer” department (but with some good info in it) comes:
THE USE OF ARTIFICIAL NEURAL NETWORK
TO PREDICT COMPRESSIVE STRENGTH OF
Faculty member of Ministry of Energy, Iran
Yes, neural nets…
This, and several other papers, concentrate on the alumina-silicates (and want kaolin clay that is pure in that regard). I suspect that the various other clays with things like Fe and Mg and such in them will also make fine liquid stone, perhaps even make things that look like diorite and granite. Things with more feldspars in them. (Or feldspathoids that have more hydration).
At any rate, the paper claims to find that you can predict a variety of properties based on various ratios of components. Looks well written and generally does a nice job.
A long time ago I had to learn this little graph / chart in a geology class. (Back when I was on a “become a geologist” kick). It’s very informative and not at all as hard as it looks.
The basic idea of this thing is that you get different rocks depending on how much of just a few elements are in the mix / melt. My belief is that you ought to be able to get similar geopolymer rocks with similar element ratios.
A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogic composition. The acronym, QAPF, stands for “Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)”. These are the mineral groups used for classification in QAPF diagram. Q, A, P and F percentages are normalized (recalculated so that their sum is 100%).
So Quartz is SiO2. More diatomaceous earth or Silica Fume, you head toward the Q end, less you move away from it. Alkali Feldspar have more potassium and sodium in their formulas. Use more lye or sodium silicate, you move more that way. Feldspars make up most of the rocks in the world, so it’s worth getting to know them.
Feldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up as much as 60% of the Earth’s crust.
But it isn’t just sodium, potassium, and calcium. You can have other metals in those positions. (Oh, as a sidebar: Notice that most of the rocks of the world have aluminum in them? That’s part of why I’m not excited about aluminum cookware… You are soaked in water that has spent millions of years in contact with aluminum compounds. It’s pretty inert and you are well adapted anyway…) But back at the main point: You can find things like Barium Feldspars too. It’s more a concept than a fixed list…
Then there are the feldspathoids. Almost a feldspar, but some of the ratios are a bit wonky… so it’s “close to a feldspar”, sort of. Nature and rocks are not always precise and orderly… From the wiki: “The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks.” so if your melt was low on silica, you get a feldspathoid instead of a feldspar.
So my assertion would just be that as you mix your “stuff”, you can shift the product around on the QAPF diagram (well, not exactly… it is for igneous rocks and we are making a polymer at lower temps of SiO2 and AlO2, so some bits will vary… but my guess is that things will be rather alike in some ways too.) So too little diatomaceous earth or Silica Fume, your rock will be more feldspathoid like. Put in some extra, more toward the Quartz end of the diagram. And so on.
All purely speculative, but a framework for conceptual investigation.
Oh, and “Cement Chemists” get tired of writing all the O2 and O3 and what all, so they made up their own confusing notation where S isn’t Sulphur, it’s Silicon and so on. As this shows up in some of the papers, here’s a guide to it:
You will see things like C-A-S-H ratios that stands for Ca Oxide, Aluminum Oxide, Silicon Di-Oxide, Water ratios.
C CaO Calcium oxide, or lime
S SiO2 Silicon dioxide, or silica
A Al2O3 Aluminium oxide, or alumina
F Fe2O3 Iron oxide, or rust
T TiO2 Titanium dioxide, or titania
M MgO Magnesium oxide, or Periclase
K K2O Potassium oxide
N Na2O Sodium oxide
H H2O Water
C CO2 Carbon dioxide
S SO3 Sulfur trioxide
P P2O5 Phosphorus hemi-pentoxide
And, on the topic of “been found before”, this tidbit: Seems that in the 1800s a guy figured out how to use this kind of reaction to make silicate mineral paint
While lime-based binders carbonate under influence of carbon dioxide and water silicate-based binders (usually potassium silicate resp. potassium water glass) solidify under influence of CO2 and in contact with mineral reactive partners form calcium silicate hydrates.
As lime paints (aside of Fresco-technique) are only moderately weather resistant these today find application primarily in the field of monument preservation. When mineral colors are mentioned nowadays these are commonly understood to be silicate paints. These are paints using potassium water glass as binder. They are also called water glass paints or Keimfarben (after the inventor).
The special composition of silicate paints grant special properties and qualities. Mineral silicate paint coats are considered very durable and weather resistant. Lifetimes exceeding a hundred years are possible. An example for this is the city hall in Schwyz(Switzerland) which received its coat of mineral paint in the 19th century.
Mineral paint contains aside of inorganic colorants potassium-based alkali silicate (water glass), also known as potassium silicate, liquid potassium silicate or LIQVOR SILICIVM. A coat with mineral colors does not form a layer but instead permanently bonds to the substrate material (silicification).
The result is a highly durable connection between paint coat and substrate. Above that the binding agent water glass is highly resistant against UV light. While organic binders such as dispersions based on acrylate or silicone resin under UV over the years tend to grow brittle, chalky and develop cracks which finally result in damage to paint coats, the inorganic binder water glass remains stable. The chemical fusion with the substrate and the UV stability of the binder are the fundamental reasons for the extraordinarily high lifetime of silicate paints.
Silicate paints require siliceous substrate for setting For this reason they are highly suitable for mineral substrates such as mineral plasters and concrete. They are only of limited use for application on wood and metal, though. The permeability for water vapor of silicate paints is equivalent to that of the substrate. This effectively means that silicate paints do not inhibit the diffusion of water vapor. Moisture contained in parts of a structure or in the plaster may diffuse outward without resistance. This keeps walls dry and prevents structural damage. This addition helps avoid condensation water on the surface of building materials. This reduces the risk of infestation by algae and fungi. The high alkalinity of the binding agent water glass adds to the inhibitive effect against infestation by microorganisms and completely eliminates the need for additional preservatives.
So if you have some rocks to paint, you can paint them with a silicate paint… This gives me some ideas for how to make that permanent library of wisdom. Some nice silicate rock tiles then just silk screen the suckers with silicate paint…
This is another of the Iranian papers. Again well written. Similar to the other one.
MODELING OF COMPRESSIVE STRENGTH OF METAKAOLIN
BASED GEOPOLYMERS BY THE USE OF ARTIFICIAL
Amir Kamalloo, Yadolah Ganjkhanlou, Seyed Hamed Aboutalebi and Hossein Nouranian*
Materials and Energy Research Center, P.O. Box 14155-4777, Tehran, Iran
(Received: December 19, 2009 – Accepted: July 15, 2010)
The results showed that
optimized condition of SiO2/Al2O3, R2O/Al2O3, Na2O/K2O and H2O/R2O ratios to achieve high CS
should be 3.6-3.8, 1.0-1.2, 0.6-1 and 10-11, respectively. These results are in agreement with probable
mechanism of geopolymerization.
Keywords Artificial Neural Network, Overfitting, Geopolymer, Compressive Strength, Metakaolin
Points out just how much silicate chemistry matters to the earth surface
The Silicates are the largest, the most interesting, and the most complicated class of minerals by far. Approximately 30% of all minerals are silicates and some geologists estimate that 90% of the Earth’s crust is made up of silicates. With oxygen and silicon the two most abundant elements in the earth’s crust, the abundance of silicates is no real surprise.
So when you add in the other odd silicates, it jumps up to 90% of the crust… The list of minerals is nice to look over. It has things like more of the Iron silicates and things like zinc and zirconium silicates (zircon). I think this points out that in theory you could use all sorts of odd clays and still get some kind of rock out of it.
These folks are looking to use geopolymers to make biomedical bits. Think things like teeth and bones and such. It also lists particular formulas.
In this study three different geopolymer compositions have been investigated and characterized as potential biomaterials. The first two geopolymer formulations are mainly composed of metakaolin, with some silica additions in order to achieve a Si/Al molar of 2.10 while the third one contains a reduced amount of metakaolin and comprises mainly of silica gel with composition: H24AlK7Si31O79 with Si/Al = 31. Further, NaOH pellets and sodium silicate (Na2SiO3) were added in the first two formulations in different concentrations as activator and ligand, respectively, while KOH additions were made to the third geopolymer formulation (separately or jointly with potassium silicate solution). Room temperature consolidation was followed by thermal activation of composition with Si/Al=31 at 60 °C for 150 min and at 500 °C for 180 min.
These folks look at adding “phosphorus slag”. I don’t know why you would have that laying around, but if you do, it can be made into synthetic rocks too…
In this study, metakaolin plus different weight percent of phosphorus slag (10-100 wt. %) were used in preparation of
geopolymer. The compressive strength, phase analysis and microstructure changes were compared with a metakaolin based
geopolymer control sample. Results showed that the substitution of slag up to 40 wt. % instead of metakaolin increase the
28 days compressive strength (14.5 %) compared with control sample. This enhancement of strength is related to coexistence
of geopolymeric gel and C‒S‒H gel or C‒A‒S‒H phase by XRD and FTIR study.
This is someone’s thesis. Looks at both sodium and potassium activated formation. Has a nice bit of historical review, some methods, and the usual bibliography of a Masters Thesis. We also get a couple of more ideas how to find earlier work (but after the Egyptians and Roman Pozzolan methods… we do seem doomed to keep forgetting and reinventing this one.)
Geopolymers recently emerged as a new class of inorganic aluminosilicate polymeric materials. These materials were synthesized for the first time in 1940 by A. O. Purdon  and again in the late 1950‘s by Glukhovsky . The term geopolymer was introduced by Davidovits  in the early 70‘s to denote their inorganic nature (“geo”) and structural similarity to organic polymers (“polymers”), and is commonly used nowadays
We also get a bit of confirmation of the flexibility and that the speculation about Ammonia might even be viable:
The activating solutions are based on aqueous solutions of alkali hydroxides and the most commonly used metal alkaline activators are Na and K . However, other metals from group I and II of the periodic table as well as NH4+, and H3O+ may also be utilized for synthesis [6, 7]. The silicon content of the final product can be manipulated by the addition of SiO2 to the alkaline aqueous solution.
This guy finds that adding sand makes it stronger. Plenty of room here to play with quartz sand vs feldspar sand too…
The effect of adding sand (40 wt%) on their mechanical properties was also determined. The K1c values increased upto 65% and E values increased upto 80%compared to samples free of sand. However, CCS and MORvalues did not change much and gave mixed results.
And, of course, the one we started with:
That still has some wonderful images in it. I also like the way his recreation of the Egyptian method is so simple:
Lime, Clay, Natron.
But the most interesting point is that this chemical reaction creates pure limestone as well as
hydrosodalite (a mineral of the feldspathoids or zeolites family). 
Si2O5,Al2(OH)4 + 2NaOH = > Na2O.2SiO2Al2O3.nH2O
kaolinite clay + soda = > hydrosodalite
Chemical reaction 2:
Na2CO3 + Ca(OH)2 = > 2NaOH + CaCO3
Sodium carbonate (Egyptian natron) + lime = > soda + limestone
Summary of the re-agglomerated stone binder chemical formula:
clay + natron + lime = > feldspathoids + limestone (i.e. a natural stone)
Now I doubt those old Egyptians were hunting all over for pure Kaolin Clay, and I’d bet their lime and natron were simple burned limestone and burned sodium carbonate. All in all, a pretty simple approach. It also gives a mix of silicate and CaCO3 “gel” as the binder. One of the papers above found having some added calcium around increased strength.
So I’m pretty sure that “old way” ought to work reasonably well. In theory, just a mix of “garden lime”, with some “washing soda” and a bit of “clay kitty litter” ought to work. I’m certainly going to give it a try and find out. Note that reaction 2 makes lye as an intermediary of the overall process. Precipitate some limestone ‘gel’ and get some free lye to catalyze the silicate step. Likely a bit of heat to help it along too. I’ll likely hunt up some nice iron rich red clay and see how it does too. Supposed to be widely sold for dressing baseball diamonds…
Never thought I’d find a way to tie baseball field maintenance to cat latrines to ancient Egyptians and modern waste disposal / recycle… and even making pots for plants on up to bridges and buildings; but it looks like those things are all bound by a common thread. One made of silicates and alkali.