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ferrocement



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http://www.kgrawood.com/bb.htm

http://www.hartley-boats.com/ferro.html

http://vimeo.com/50990903

 

The above material was prestented as solution to floating concrete shells - my answer was:

 

The rebar i see in those videos is supposed (and designed) to be the “fiber component” of a 20cm strong structural concrete wall and have a concrete cover of at least 3cm (according to european concrete engineering norms) to “avoid its rusting” – so to make it part of a 2cm wall and leave it under merely 1mm concrete cover and complicate the proper embedding of the steel by “littering the place” with chicken wire that hinders as proper void free embedding of the fiber component into the cement matrik additionaly, is a “clumpsy and unwise use of the fiber component” at best. In fact it is “utmost surprising” that there are shells that where built with that kind of method that do NOT rust and fall apart in a decade. That talks good of the “craftiness” of their builders in the sense that they got relative good embedding in spite of the chicken wire hindering them. If i would have the task to figure out a method to produce “short lasting shells” i would really choose something like that…a good shell will last 200 years for sure and probably 2000 years (as the Panteon) without showing minor signs of decay – so the fact that a few “ferrocement shells” last a couple of decades does not say a lot either. When talking about seasteading we need foundations that last centuries or millenia in marine ambient – i doubt that methods like shown in the videos and pictures are up to that task.

I would suggest to look into the following:

1) do not use steel rebar if you can not assure a proper embedding depth of 3cm.
2) forget the clumpsy chicken wire.
3) find a better method to hold the wet matrix material in place while curing than chicken wire.
4) explore non rusting fiber components where the required cover of 3cm can not be achived.
5) keep steel reinforcements out of the “spashzone” where corrosion is expected to be worst.

Basicly ferrocement is only on the table because it was the “first idea” of Joseph Monier to introduce some kind of fiber into a cement matrix and get a composite material out of it.
http://en.wikipedia.org/wiki/Joseph_Monier
Like always the “first idea” almost never is the “best idea” the better ideas come if you give it a second third, and fifth tought – that include feasible solutions to the above list of issues. Just forget “ferrocement” and think about smarter fiber components and smarter fillers and smarter aplication methods, do a series of tests find the better way. With space age fiber components and understanding of shell structures at hand we can really do a better job than the “ferrocement” invention of Monier…



-- Edited by admin on Thursday 27th of March 2014 04:44:50 PM

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www.seasteading.org/forum-list/topic/floating-concrete-shell-and-honeycomb-structures/page/2/

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I would be a bit concerned about voids, rebar rusting and adequate steel embedding in that process…honestly i have seen smarter ways to build shells, especially to “introduce the fiber component” into the build. Would consider this close to “worst case scenario” for producing a rusting rebar desaster in a marine splash zone ambient.
http://vimeo.com/50990903



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The idea that concrete items are known as " little flexible " was presented in the thread, - this is my answer...


Concrete beam flexing under load.
You need to open to the idea that concrete in the widest sense is a composite material containing 3 elements binder (cement) fibers (rebar) and fillers (aggregates) – the property of the material is in the COMBINATION of components – not in the one of the components. The idea that concrete has a similar material property as a cement block is so fundamental wrong like the believe that a “carbon fiber composite part” has a similar behavior to coal. Whenever you combine the 3 elements right you will get a piece that has excellent flexibility great tensile strenght – so all the “problems” you try to solve with a incredible complicated “attachment sistem” are basicly “imaginary problems that arise from a wrong perception of the material”. If you build a hollow concrete beam – and do it right- you do not need to treat it like an egg – in general when you put concrete and steel together you use welding of rebar sticking out of the piece, cast jointing, bolting, epoxi bonding, grouting, as attachment technology.



-- Edited by admin on Thursday 27th of March 2014 04:50:20 PM

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floating concrete shellfloating concrete plate

Floating Conrete Shell and Honeycomb Structures emerge as “Technology of Choice” for Seasteading. They combine the durability needed for oceanic real estate, with the toughness required for handling climatic tail events, like Draupner waves and Hurricanes. This thread is dedicated to explore the “how to implement” of this technology for ocean colonization and floating business ventures. On large scale and on small scale. As the world becomes more and more ocean oriented it is predicted that the twenty first century will see more construction activity on the water then on dry land.

See more pictures on what is out there already on shell building and thin shell domes at:
http://www.pinterest.com/wellmer/concrete-shell-building-thin-shell-domes-honeycomb/

See more pictures on oceanic concrete shell building:
http://www.pinterest.com/wellmer/oceanic-concrete-shell-building/



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honeycomb shell float
Statfjord C base honeycomb shell.
floating concrete shell


Small fiber concrete float.


Many different aproaches are feasible – just analyze the costs and you will see that you can build a simple shell or honeycomb structure that gives you the same amount of real estate squaremeters at 20-50 times less cost (than a steel structure) – so as long as “housing” is the purpose i see no good reason why to include expensive steel structures into a project.
You can build such honeycomb shell structures incredible big (like statfjord) as well as incredible small and everything in between you also can build andy shape you can imagine .



So where is the benefit of building complicated and expensive steel structures.


The idea is to get most bang for the bug.



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