What is Seasteading Cement?

In our past blog posts up until now, we have often referenced Seasteading Cement. But what exactly is Seasteading Cement? Well to answer that, we should first talk about what it isn’t, and why we had to create it.

Which materials are best used for seasteading, and why were none of them good enough to fill our very particular seasteading niche?

When most people think about permanently living at sea, they will assume that the easiest way to do that is with boats. But boats and ships are designed only for transport. They become very unstable in rough weather and require constant maintenance, in addition to having much of their internal space dedicated to an engine, which a mostly stationary structure has no use for. These problems have already been addressed with deep-sea oil rigs. Oil rigs are much more stable, durable, require less maintenance, and are more spacious for their crew. They are purpose-built and very good at their job, but oil rigs are expensive, with some of them costing billions of dollars. If we want a cost-effective seastead, it must also be purpose-built, just like oil rigs were built to drill oil, seasteads must be built to safely house people and industry. Before working on a design, you must first decide what materials you are going to use. This is where we began our journey of inventing Seasteading Cement. Now let’s look at the pros and cons of each conventional building material:

  • Steel:

Steel is a classic material, and it is used to build both ships and oil rigs, so it seems like a no-brainer that we would use this material right? It has a great strength-to-weight ratio and is cheap and easily accessible. Well not so fast. Steel is primarily made of iron, and iron rusts, especially in salt water. Massive cargo ships are cost-effective because they are dry-docked every few years and repainted with anti-rusting paint. Their hulls are often 2 inches thick of solid steel so that if some parts rust it won’t rust all the way through, even then most large vessels only have a service life of less than 40 years. How would you like it if your house was expected to last less than 40 years? And that is assuming proper maintenance. Pulling a seastead up out of the ocean every couple of years and repainting is not feasible for many reasons. How could this even be done for a community of hundreds in the middle of the ocean? Once a seastead is placed somewhere in the water it is not moved as easily as a boat. Oil rigs get around these problems by sheer scale, they are simply so massive and their walls so thick that they can have several inches of steel which takes a much longer time to rust. They also cover themselves with expensive sacrificial anodes which slows down the rusting process. For longevity concerns, steel is not an optimal material.

  • Seacrete / Biorock

We have talked about Biorock before. It is a material that forms when you take a conductive filament like steel rebar, graphene, or a few other materials, and run a small electric current through them while attached to a sacrificial anode. The material that forms is roughly as strong as concrete, capable of handling about 3,000psi of pressure. This allows you to grow your seasteads in the ocean, with your only expenses being the rebar skeleton of the structure and some floating solar panels to keep the process going. but those solar panels are going to have to be durable because the speed at which seacreate grows can be very very slow. The seasteading community has carried out many experiments over the years with seacrete and has found growth rates anywhere between half an inch and 3 inches per year. This means that if there is one foot in between two pieces of rebar it would take several years to fill in that gap. Here at Arktide we have carried out similar experiments and found similar results. One workaround may be to use sheets of metal mesh rather than solid rods to form the accretion surface, as this would reduce the amount of Biorock you need to accrete, but this trade-off has shown in our experiments to slow down the accretion process as well. In the end, while Biorock is cheap, it is also slow, and a little on the weaker side compared to modern concretes.

  • Concrete

Ok, so then what about concrete? Well, concrete boats have been made in the past, and while they are usually slower, they are also cheaper. For a seastead this seems to make perfect sense then, just build them out of concrete. But anyone who has driven by a concrete bridge before may have noticed something; cracks. Cracks in a floating concrete structure could quickly lead to flooding, and any family onboard a sinking house is sure to wish that their home was made of steel instead. It isn’t just the cracking either, but salt water seeping into the pores of concrete can cause slow chemical reactions that will weaken the concrete over time. In addition to these problems, normal concrete slumps, but doesn’t flow. What this means is that air pockets are likely to form in the finished structure increasing leakage, decreasing strength, and limiting the material to only be used in large walls. Normal concrete can’t be used to make a half-inch wall very easily. Typically because of its low flowability it is used to make walls or parts that are at least 4 inches in width. We decided that we had to create a new material, something similar in price to concrete that wouldn’t crack and would be more workable so we could make the thin precise shapes we needed to build the ArkPad.

This old anti-air fort built during WWII was made out of steel. Today it is home to Sealand, the world’s smallest country. We wrote more about Sealand in our Evolution of Design blog posts.

A pair of modern ferro-cement boats. These boats are made out of cement instead of wood or steel, they will require less maintenance and are cheaper and faster to build, but are slower and heavier in the water, they must be designed with much thicker walls and in a more ‘blocky’ style.

Seasteading Cement

Seasteading Cement is something that Arktide has been working on for over half a year now. We took inspiration from UHPC or Ultra High-Performance Concrete in determining which materials to use in its creation, although it could also accurately be placed into the Industrial Mortar family of materials. After starting with three different UHPC formulas, we altered the formulas after each series of trials and also took into account the most cost-effective materials we had available to us at the time.

We are still in the early stages of testing this material, but already at this stage we can tell some of the properties this final material will have:

  • No cracking

None of our Seasteading Cement samples cracked during their curing phase. Often if the concrete is not kept properly moisturized during curing it will crack itself even in this early stage, although staying wet in the ocean likely won’t be a major concern when we reach our deep ocean construction phase.

  • 11,000psi Compressive Strength

More than double normal concrete. Later versions of our material will reach as high as 20,000psi.

  • High flowability

Allowing us to make very thin pieces but still retain high strength.

  • Greater than 1,160psi Flexural Strength

During our initial testing phase, two of our test blocks were unable to be broken and the machines had to shut off at only 1,160psi because it was unsafe to go higher. Normal concrete has between 400psi and 700psi flexural strength, but we believe we can easily reach 1,400psi in later testing, this means that the bending motions of waves on the structure would not cause it to crack.

  • Low Water Permeability

Leakage will be much lower than normal concrete because of denser packed materials. This densely packed structure of the material is also what gives it its longevity and strength.

  • Light Weight

While concrete typically weighs about 2,450 kilograms per cubic meter, our Seasteading Cement only weighed 2,280 kilograms per cubic meter, a significant weight reduction despite it being stronger in all regards.

  • Made of Recycled Materials

At a later date, we will disclose the formula to make Seasteading Cement, but for now, we can say that many of the primary materials used in its production are recycled materials, making this a very green and environmentally friendly construction material. We believe that after it has proven itself at sea, it could be used in land-based construction as well, and may play a role in improving the future of land-based architecture.

  • Low Cost

This point goes hand in hand with the last one. Here in the Philippines where Mitchell Suchner and Andy DeOcampo have been heavily involved with creating this material, we have found sources for our supplies that allow us to get the price of our seasteading cement down low enough that it nearly matches normal concrete prices in the United States. This is one of the biggest breakthroughs we have had during its creation process, since UHPC on which this formula is based, is known for being far more expensive than ordinary concrete, with some suppliers asking for prices 4x to 10x normal concrete price. Seasteading Cement will only cost 10% to 80% more than normal concrete.

  • No Rusting

Another factor that sets Seasteading Cement apart from UHPC is the removal of any element from the formula that could react with salt water. There are no steel fibers, or other chemicals in the formula that will degrade performance significantly over time.

  • Self Healing

The final completely untested property of Seasteading Cement will be its ability to self-heal in salt water. We plan to introduce a new material into our formula at a later stage that will allow it to be used like rebar when making seacrete. By making Seasteading Cement slightly electrically conductive, a small current could be applied, so that any cracks that might form in the structure would be filled in with seacrete, this scar tissue would be immediately solid and would most form in areas where damage has occurred on the structure. This will allow ArkPads to repair themselves after storms or collisions with boats automatically, and without any repair team needing to be called.

  • 100 Year Lifespan

In later tests, we will attempt to prove our hypothesis that Seasteading Cement will last at least 100 years in the corrosive environment of the open ocean. In some tests carried out on UHPC samples in Canada, blocks of the material were placed on a beach and exposed to hundreds of freeze-thaw cycles in the cold saltwater environment. Despite the considerably damaging circumstances, even after 25 years, the blocks were almost entirely undamaged, similar testing can later take place with blocks of Seasteading Cement.


In this video, we can see a specimen of our Seasteading Cement undergoing a Flexural Strength test. In this test, a force is applied to the block until at the end of the video it breaks in half. Here, we have measured the breaking force to be over 1,100 psi. This was one of our weaker specimens, there were also other types of Seasteading Cement we carried out the same test on that exceeded the maximum strength of the machine.

So where are we now in our development of Seasteading Cement? Currently, we are waiting on our testing facilities to reopen as they have been temporarily booked by other organizations, we will also soon expand to other testing facilities to have more types of testing performed. We want to get more precise measurements of our permeability reduction compared to concrete, as well as put our test specimens under higher flexural stress to test the peak flexural strength of our material. In the coming months we can expect a lot of progress on our Seasteading Cement and changes to the formula, the final test will be when we eventually use it to create the first ArkPad and put it in the water. Then we can see how the material performs on the field, and as the years roll on, we expect it to stand the test of time.

For standard concrete and cement, the more that a substance flows the weaker it is. This means that a stiffer more rigid substance is going to end with a higher strength. But for Seasteading Cement, we have achieved a flow like water, where the material itself has no stiffness whatsoever. This allows us to pour it into any shape that we want, but it is still more than twice as strong as concrete after it hardens.

This is an example of a structure that could only be built with flowing materials. Stiff materials like concrete couldn’t be used to create organic flowing shapes like this very easily, but thin and flexible forms can be more easily achieved when your material is flowing.

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