Geopolymer Concrete, the perfect seasteading material


Can a basalt fabric be cast into two geopolymer panels, such that the basalt fabric is between and connects the two panels, and acts like a hinge? If so, what would be it’s lifetime in flex cycles between 180 degrees and 90 degrees, with no real loading on the hinge? The goal would be to replace a piano hinge, keep water out, and last forever in salt water.

Or any other configuration of fibers. For this scenario, painting the basalt fiber in a waterproofing (such as latex, neoprene, etc) is acceptable.


An url on someone or sometwo experimenting with geopolymer mixes:

And some pdfs:


So, after the foofarah on the “City Sewage and Food Supplies, as a combined topic” thread, did anyone beside me figure out that Sewage Sludge Ash might be a feasible ingredient in geopolymer making, as well as having the potential to pay for the bulk of the material to substitute geopolymer for cement in ferrocement construction?

Cities pay to have SSA hauled off and disposed of. At a pH of 6-12, it should be reactive enough to create a suitable geopolymer.

Currently, I’m working with Diatomaceous Earth and Fullers’ Earth ,a pair of nearly universal, budget-conscious ingredients, with outstanding potential. If I can get my mitts on some SSA, will be trying to work up a formula…

DE and FE are generally cheap enough that getting paid to haul off SSA, might well pay for the other 2 ingredients… 85% of ferrocement construction is the cement… 85% of the material to build a seastead could potentially be FREE, using the income from SSE to buy the others…


Another useful material that one can sometimes get paid to haul away is fly ash, from burning coal. Actually quite useful for making concretes that cure underwater – and very strong/tight (low ion migration) when cured!

However, I’ve heard that the permitting to move the stuff can be a total deal breaker. So IMHO, the longer-term prospects may be good, but be careful not to land yourself in regulatory hell!

Fingers crossed for this, it’d be an elegant solution, if the SSA works in geopolymers.



Application of fly ash-based geopolymer as an alternative material for plug and
–Silje Ramvik


Good find!

IMHO, that thesis has good, basic explanations of the cement-making processes and explains the chemical compositions and roles of key ingredients of both Portland cement and Geopolymers.


The problem with Portland Cement in concrete and/or Geopolymers is its’ hydrophilic nature, which makes it susceptible to deterioration, when exposed to water. On a seastead, the problem would be even worse…



I must respectfully disagree that the hydrophillic nature of Portland cement is really a problem for marine applications. Many huge, made-with-portland-cement offshore drilling platforms, etc. have shown IMHO quite respectable strength/robustness to some very challenging sea states, as in the North Sea. It’s also well known that adding natural or artificial Pozzolans (in sane ratios, mind you) generally improves the strength and lowers the ion-migration rate in conventional cements.

IMHO, another take-away lesson is that the material strength is related to the bond strengths of the constituent materials. I’m not surprised that Calcium compounds’ bond strengths (esp. with Oxygen) are lower than those of Aluminum and Silicon.

Again, be careful of both regulations and general safety issues with fly ash. And IMHO, don’t breathe the dust of cement/geopolymer-making materials. (Note that Silica fume is really fine stuff, I advise caution when working with Silica fume in its dry powder state.)


The difference would be similar to the problem with corrosion of iron reinforcement, as we see in Americas’ concrete structures that deteriorate rapidly, vs the use of pozzolanic ash, as was done in ancient Greece. Greek Concrete has survived the ages, weathered and worn, but not as easily damaged, either.

The more caustic environment of Geopolymer vs Portland Cement will inherently provide superior protection of ferrous reinforcement, which, currently, is considerable more budget-conscious than Composite reinforcement.

That said, IMHO, the combination of Basalt composite reinforcement and geopolymer cement has the additional benefit of zero corrosion and the ease of repair, given that geopolymers will adhere to geopolymers, while Portland cement based mixtures rarely adhere well.

In addition, the lower ion transmission of geopolymer will aid in the reduction, or even prevention of bi-metallic corrosion, which can be induced simply by having an electrical shore connection, and grounded metals in the hull structure, using the water to complete the circuit.

Another benefit is heat tolerance. Portland Cement based concrete dissociates and has spalling, when exposed to fire, where Geopolymers, not being bound with water, do not have that problem. The difference is in the chemistry. While I’m an amateur, if I don’t understand the equations, I can still understand the descriptions of the differences, as well as knowing real-world problems with concrete.

IMHO, the inherent properties of the combination of Basalt reinforced Geopolymer far exceed the properties of ferrocement, in too many areas to ignore. By having access to a suitably low-cost geopolymer, the added expense for higher-priced Basalt reinforcement will be mitigated in the durability and ease of repair.

If I can get the mixture ratio and technique simplified, the finished cost may equate to current ferrocement construction, using similar techniques, meaning it is also a familiar process.

Just on my current basic formula, I’m already below Portland Cement based mixtures in cost. If added expense of Basalt reinforcement raises it slightly above ferrocement, for a vastly superior product, then it’s a win/win situation.


I should say pozzolans plus volcanic ash, vs pozzolans and slaked Lime.

About due for another nap, and it shows in my explanation. Getting to where I can sleep for about 3 hours at a stretch, with the C-PAP, if I use Benedryl and Melatonin to help me sleep…


I offer a specific caution, that high alkalinity/pH can cause problems with some aggregates:
The search phrase you probably want is: “Alkali–aggregate reaction”

The PCA’s explanation is here:

Wikipedia also has a page, IMHO not as good as the PCA’s

Note that this is an issue for some, but not all, types of aggregate.


Since, for practical purposes, we’re talking of typical ferrocement style construction, rather than poured slabs, any aggregate will be sand (up to #8 screen, I presume)… I haven’t looked into Geopolymer/Aggregate ratios, not even sure if it’s necessary, as of yet. Experimentation will tell…


Influence of aggregate content on the behavior of fly ash based geopolymer concrete

Benny, Joseph A.; George, Mathew B.

Guesstimate: 4:6 Geopolymer : Sand… ~$200 for 10 tons geopolymer, ~$285 for 15 tons Beach Sand ($19/ton according to- )

Now we have 25 tons of dry geopolymer cement mix, for roughly $500… :neutral_face:

PS- Using non-metallic composite rebar allows the use of seawater, which also has a caustic component value… All the chemical reactions are facilitated by water (H2O), but, once the reactions are done, the geopolymer cement becomes hydrophobic, so dissolution is far less likely to occur. Still, this will need lab-testing and verification, before taking it as ‘gospel’…


Sorry. Brain-fart. The Hygroscopic nature of Portland Cement… In my deffence, I was running on fumes, and exhausted, when I was trying to write that,

(Wilfried Ellmer) #199

Geopolymer is probably a good candidate for “new building sistems” that depend on a regulation free space to be applied. Civil engineering on land is probably one of the most ruling infested areas you can think of - composite technology applied on the ocean can be somewhat different.

Today we see that oceanic engineering is rather regulated by private classification societies (Lloyds, ABS, GL, than by state rulework, legislation, and jurisdiction…and this works just fine.


With my initial batch attempt, I brain-farted 2 different ways. Too much Base and no aggregate. Needless to say, it flopped in several ways. After totally drying, it wasn’t quite as sturdy as a mud-dawbers’ nest. I was able to put my weight on the sample, before it failed. But…

I now have a sample curing of 60/40 sand-to-dry, mixed ingredients for geopolymer, consisting of 3 pts Fullers’ Earth-to-3 pts Diatomaceous Earth-to-4 parts Super Soda (Sodium Carbonate).

Initially, I added water to dry mix, then added more dry mix to get a better consistency. This is onr of those formulas designed to hopefully allow working as a plaster and ambient temp curing, based on the stuff I’ve read.


A further thought…

Using siliceous beach sand could eliminate the need for Diatomaceous Earth, as a source for the silica in the chemical bond… Seems the more I think on it, more possibilities open up…

Side Note: Sample is definitely of a higher density than my previous attempt. I’m hoping that’s a good sign. It was definitely ‘set’ before I removed it from the cup/mold. So it does cure at modest temperatures (~72*F), within just a few hours.

Still undecided on how to do effective testing. Definitely need a water test, to ensure water resistance, some sort of compression test. Probably a fire test using a torch, just for general purposes.

I would definitely like something more reactive… Lye is on the list of potential Bases to use for the formula… Drano has Aluminum added, which limits the interaction with the DE and FE. Wife will be getting me some lye from a soap-making supply shop she’s planning to visit…


What is a geopolymer? Introduction

May 11, 2014 |
updated: August 17, 2012 Geopolymers are chains or networks of mineral molecules linked with co-valent bonds. They have following basic characteristics: a) Nature of the hardened material: X-ray amorphous at ambient and medium temperatures X-ray crystalline at temperatures >500°C b) Synthesis Routes: alkaline medium (Na, K, Ca) hydroxides and alkali-silicates yielding poly(silicates) – poly(siloxo) type […]

Geopolymers are presently developed and applied in 10 main classes of materials:

Waterglass-based geopolymer, poly(siloxonate), soluble silicate, Si:Al=1:0
Kaolinite / Hydrosodalite-based geopolymer, poly(sialate) Si:Al=1:1
Metakaolin MK-750-based geopolymer, poly(sialate-siloxo) Si:Al=2:1
Calcium-based geopolymer, (Ca, K, Na)-sialate, Si:Al=1, 2, 3
Rock-based geopolymer, poly(sialate-multisiloxo) 1< Si:Al<5
Silica-based geopolymer, sialate link and siloxo link in poly(siloxonate) Si:Al>5
Fly ash-based geopolymer
Ferro-sialate-based geopolymer
Phosphate-based geopolymer, AlPO4-based geopolymer
Organic-mineral geopolymer


Stuck with what I can get my hands on, at the moment. Current prep is for 2 mixtures. Hardwood-ash, as the Base, and charcoal brickette ash, as a substitute for both the Fullers’ Earth/high Alumina Clay and for the Base.

Note: the term ‘fly ash’ is a common reference to metakaolinite, an Alumina residue from coal-burning power plants. While highly reactive, it is not a substitute for the base, but, rather, as substitute for the clay. Not everything we call ‘ash’ will create Lye.

Both formulations will be dependent upon the wood-ash portion, to supply a dry-form of caustic lye. Of note, lye can be made by passing alternating current through seawater, releasing the hydrogen and chlorine gases from the solution, and forming Sodium Hydroxide as a result of the reaction.