Geopolymer Concrete, the perfect seasteading material


Hi Dave,

Isn’t the EPIC material compression strength of 1500 psi way to low compared to 6500 psi for regular ferrocement in order to be used in the marine environment?


@Aquaponic_Dave this is really exciting. I’ve pondered whether EPS and Concrete could be combined. I really like the idea of an outer later of hard material combined in a way that makes it inherently bouyant (under 63lbs per cubic foot). This is a safety issue for floating residences, that in the case of total failure that the remnants can float. (See The Whale, Melville)

I also like that you can attach new materials later. This is a real problem with concrete that additions will not bond. I’d be interested in knowing more about this.

(Dave Pennington) #44

Hello Octavian,
Wood often has a much lower PSI rating than 1500 PSI, and yet we make boats from it. Wood also cannot be molded into compound curves at any thickness desired, these two features allow EPIC to be used for making many things you might not yet imagine. Deep water submersibles could be made, with external ballast to make it sink. This type of craft would float no matter what as long as the ballast could be released.

(Dave Pennington) #45

Concrete has been combined with EPS, I do not use sand or stone so it isn’t concrete anymore, its a cement composite.

Portland cement does not actually bond very well with EPS, because EPS is a very slippery molecule. Cellulose fiber infused with cement (“papercrete”) can and does form shells around EPS beads when mixed properly. These shells create a flexible and durable matrix, and the flexibility of the EPS allows the minor amount of papercrete shrinkage to occur without issue. By using recycled EPS EPIC can be made cost effectively and the material has many other useful qualities as described.

The fibrous surface can be prepared and attached to new material into a monolithic whole, where the connection point is as strong as the surrounding material. The techniques for this bond are simple enough for most people to accomplish easily once mastered. The ability to add to an existing structure is a big leap forward, especially since EPIC is impervious to water damage. Given these properties a piecemeal approach can be used, where additional sections are added on without concerns for protecting the previous layers from the elements. When modifications are needed (adding wiring, plumbing, windows, etc) the cured material can be cut open and any material removed can be reground into new EPIC.


That’s a big drawback,…

(Dave Pennington) #47

I have used the Monolithic Dome techniques for several years, they offer significant advantages over conventional forming. They did not invent the technique but they are the most advanced practicioners. Their airforms are not cheap, to be sure, but they can be extremely durable and useful. In this application the balloon would be inflated and then sprayed from within to form the torus and bulkheads. The internal airform method allows the structure to be created in a controlled environment without weather delays. Using GFRC and other advanced concrete materials would allow the torus to be created quickly using shotcrete equipment during calm weather. Once the shell was completed additional layers of EPIC composite could be added to create structural insulation.

(Dave Pennington) #48

It may be that other materials will be better suited to the waterline applications. They have their own limitations and combining materials in the best way possible should be the goal, not using one over another altogether. One of the advantages EPIC offers in addition to low cost and buoyancy is a fiberous surface layer which can bond well with many coatings, unlike conventional concrete which is more difficult to bond with due to its crystalline structure. Coating it with polymers which are impervious to ocean accretion should be possible.


I remember seeing it (minus the poly beads) used as 2ft by 4ft roof panels in the 1960’s. It was advertised as fireproof, sound dampening, cheap, and thermally insulating. Being coated in thin cement, the paper was said to be bug proof because of the cement’s pH. It did not tolerate being walked on when used as a sidewalk, it eventually crushed down. It likely would not be allowed nowadays unless coated over, as it would shed fine cement dust occasionally, when moved or flexed.


Not really. It’s the same as a house. You normally use paint or some outer coating to provide a flexible seal. Keep in mind that almost all new houses are constructed out of particle board.


Well, I would be very careful about using an untested material to build the hull of a future seastead. With ferrocement, we know for sure that it is strong and it would last at least 45 years (so far). Nothing against Dave’s EPIC material.


What is the example of floating concrete that has lasted 45 years?


I think one of the concrete ships in Powell River has floated continuously since before 1950, but i cannot prove it. That is, i cannot say which ship sank on purpose, or which never sank. I am pretty sure none have carried any loads at all, or been on the ocean, in over 45 years.


40 years +,…



None of the boats listed were floating over 45 years ago. Granted, a few are over 40 years, but that wasn’t the question.


Octavian, thank for the search. It really proves the point.

Yachts are high ticket, high maintenance items. In addition, hardly any yachts have been made with ferroconcrete hulls since 1980.

I used your search to show Ferro-Cement boats from 1980 to 2000. There are 35 of them. Then I searched for all hull types. There are 35,000 of them. So we are saying that 0.1% (0.001) of boats are made with concrete hulls. There are 76 boats made with PVC, so PVC has twice as many as concrete.

So what we are needing is maintenance free platforms. Examples of platforms sitting in the ocean, and how durable and long lasting they are. Can you find any other examples of a concrete platform that is 45 years?

Maybe we should look harder at normal steel hulls like bulk carriers use.



Most of the boats shown there are built mid 70’s. It means that they were floating back then…

[quote=“KatOnTri, post:55, topic:240”]
but that wasn’t the question.

It was exactly the question,…ferrocement IS floating concrete.

I am getting really tired of your idiocy, KatOn.


1980-2015 ferocement boats for sale. 50% more boats here than the 1960-1980 search.

Please keep in mind that there is no such thing as “maintenance free” in the marine environment,…It’s either high maintenance (steel, wood, fiberglass) or low maintenance (ferro or concrete).


45 years ago was prior to 1970. All the boats you showed were built after 1970.

What idiocy? He said “lasted 45 years”, and you did not list any boats 45 years old.

(Anenome) #60

In the 1970’s ferrocement craze, concrete sailboats logged millions of oceangoing miles around the world, including circumnavigations. They tended to last about 10 - 15 years without extraordinary maintenance.

The goal with geopolymer + non-ferrous fiber reinforcement is to address the material shortcomings of that design which was its achilles heel.

Low-calcium geopolymer (type-F) won’t rot in seawater, one of the very few materials on the planet that will not, and fiber rebar will not rust–completely removing the major failure mode of concrete: spalling due to rebar rust and expansion.

What’s needed is just to make a low permeability geopolymer and make sure the structure is strong enough, and the results should be exceptional.


Kool. Can you say how thick the cement hulls were? Was the thickness adequate for strength? Was it too overly heavy compared to a same-sized non-cement boat?