An island built on floating cement balls
November 6, 2011 at 5:03 am #16190
There was some experimentation here, http://pelagic.wavyhill.xsmail.com/ . Only issue I see is infiltration of water into foam cells gradually adding weigtht over time. Monolithic domes use a moisture barrier for underground construction. Do you have any moisture coming through the concrete submarine walls or do you coat the outside with some kind of moisture barrier?
IMF, http://www.floatingstructures.com/ builds floating structures using a reinforced concrete shell around an expanded polyethylene core.November 6, 2011 at 2:31 pm #16195
it is seems much more economic and feasible in logistics and materials to build a floating honeycomb along the lines of condeep baseplate structures , similar to glomar CSDI or similar to Nkossa. Than doing some “messy process” like foam on large scale.
That kind of honeycomb has not only been built and tested for 3 decades on open ocean already – it is also clear that you can downsize the building size to just a few squarmeter of floating structure as we have done it here in a couple of experimental projects in cartagena.
A “cell size” of about 1m diameter works just fine.
What form, shape, building method the cells of a modular island have is more or less trivial and without any major importance. Balls can work just the same as cubes or hexagons – just don’t overengineer it – keep it simple keep it doable in mass production, keep it doable by an average concrete worker. (see more)
What really matters is that you can build a ton of buoyancy with 2 workers in a day at a cost of 166 USD (that are the global figures we have achieved already on our pilot projects sites) – and you can go on building and growing your modular islands as long as you have money in the project account to support building.
concretesubmarine.comNovember 6, 2011 at 7:38 pm #16200
I wouldn’t go for a ball, specially when building in ferro, but rather a simpler shape, as Wil posted above. The reason should be the KISS principle in regard to the actual ferro construction. It will be more time consuming and therefore more expensive to build the spherical mesh required for ferro, rather than a flat one.
It will also be harder to plaster a spherical mesh at the same thickness, on the outside, to start with. And keeping that thicknes constant all over the mesh is very important in ferro, since if you don’t, when dryed up, the thinner areas will be prone to cracking and therefore seawater infiltration that will rust your mesh and create structural failiure point here and there. Not good, since you might end up taking water,…Another question that arises is how are you gonna plaster the INSIDE of that sphere? There is no way in hell to do that, for small diameters. (bigger ones, lets say over 6′ diameter you could get inside and get the job done) For ferro to achieve its nominal strength will have to be plaster on the both size of the mesh,…
IMHONovember 6, 2011 at 8:36 pm #16203
The sphere only makes sense to me if it can be cast. What is the breakdown of the $166/ton in materials, labor, overhead? This isn’t too bad.
A 40 foot shipping container weighs about 4 tons, so this would be $664 to float the container, double it at $1328 to float a 40′ container and have almost 8 tons payload. Used shipping containers sell for around $3500, so were looking at $5000 for 8′x40 = 320 square feet, about $16/per square foot.November 7, 2011 at 2:56 pm #16214
A floating island has to apply to the following parameteres.
1) build afloat
2) build modular
3) build from concrete
4) keep it simple
5) start it small
6) keep modules small but not too small
anything else has been pretty much ruled out as “little feasible” in funding terms. I would categorize foaming as a sub method of “small irregular bubble space building” – where the downside is that the space in the cells can not be used due to its almost microscopic size and the material to bond the cells to each other is expensive.
I am a fan of methods where these downsides can be avoided .
Are you suggesting containers as bubbles in a concrete matrix ? – use containers as form is expensive – a reuseable airform can do a better job at much lower cost.
What has been done on floating concrete structures in island size so far is roughly rounded up here (outstanding floating concrete structures) – floating islands of any kind will follow that proven technology path that consists basicly in taking the concrete civil engineering used on land to sea.
I highly doubt that the engineering of a floating city will be something that comes out of the blue from nowhere in materials and in construction techniques.
It will simply evolve naturally as consequence of something that is there already.
concretesubmarine.comNovember 7, 2011 at 7:08 pm #16216
It would be easier to cast the balls from foam concrete and spray coat them with a thin solid layer of cement. This also prevents sudden loss of floatation due to cracking or breaking spheres. I would also add glass or steel fiber to the mix for much higher strength. Unlike steel rebar, steel fiber only corrodes in a millimeter from the surface of exposure to seawater. Allied Foam Tech, http://www.alliedfoamtech.com/Appconc.htm , lists densities as low as 30 kg/cubic meter. This means up to 970 kg or about half a ton floatation per cubic meter, a 1.24 meter diameter sphere. Using Ductal, http://www.vsl.com/index.php?option=com_content&task=blogcategory&id=24&Itemid=110%29 , the structures can flex to avoid cracking from impact as well as have a high strength.
My main interest in concrete for seasteads is to cast fiber reinforced foam concrete in molds, preferably as molded shapes ready to be outfitted and finished for habitation. With neutrally bouyant foam concrete, large structures can be cast and assembled in the water with out heavy lifting equipment, then pumped out for floatation.
This is interesting. I was likely going to make the spheres by first getting a styrofoam sphere and build the outer layer from cement. That way, if there was ever a rupture or leakage, it would still float and would take a long time before it ever sank (if you did not notice in time).
970 kg per cubic meter would be nice. The more it can lift, the more you can make the top layer of the island have more of a soil and rock layer like a real island.
My biggest concern would be the long term affects.
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