rudi sent a link to a foam building website and asked | what do you think ? |
https://floatinghomes.ltd.uk/foam-concrete.html
Establishing the “engineering baseline” | what is out there and working well already | what is not | what is “floating conrete technology” in use as we speak |
In general terms i would say that the combination of concrete foam and water under hydrostatic pressure is a reciepe for calling in disaster.
It appears in the picture that they propose to cast foam on the watersurface directly.
I would expect a build like this to suck up literally tons of waters per day and sink after a week.
Now they claim to have a “foam that does not suck up water” - but like a unicorn this is a thing erverybody has heard “talking about” but nobody has seen it in the zoo yet.
So the approach i suggest is a conservative one.
Before declaring a “wonder material that solves a problem all by its own” i suggest to never use any material in a load case where you can not point me the a dozend examples where this exact material has been used in a similar load case and worked well for some 30 years without showing any indicator of failure of any kind.
I have yet to see a “concrete foam under hydrostatic load” performing over a long time periods without failure.
Any testing that i have done shows that any kind of foam in contact with water will suck full of water every single time.
Now this picture shows a plastic sheet in the form prepaired for the pour . So you could bring up the argument that there is a “coating” that keeps the water from the foam so the foam is NOT in direct contact with water.
But a single puncture in this plastic sheet will create a complete failure of that sistem - which spells “disaster” in my engineering book.
When it comes to concrete under hydrostatic load and in direct contact with water over a long time period. It is good to establish a engineering baseline (what is prooven and tested) as we speak.
A good example how you do it is Troll A - a concrete wall of 1m holds back a 303m watercolumn there is no “coating to shield the concrete from direct contact with seawater” involved . The contact with water under high pressure is as direct and unshielded as it gets.
The sistem is working and under load since 1996 (for 26 years) has never been to to a drydock never recieved underwater maintainence of any kind, and shows no “indicator of deterioration” up today.
So there is a prooven engineering baseline for floating concrete structures which spells:
Stuff that is built with 1m thick concrete walls can float in the high seas and the life expextancy is hundreds of years ( if not thousands of years - what is yet to see - but can be expected )
Check also the cesarea harbor which is a roman concrete structure based on caission technology in good shape after 2000 years seawater exposure (it was built by “herodes the great” the man that wanted to kill baby jesus ) and the concrete is still in good shape.
Now that the first 30 years of data are in, we can expect that Troll A is on its way to a “similar durability record”
The messy foam stuff in the website above - mee - probably not…
Having said that it is also important to keep in mind that the engineers that built Troll A would not even have considered a floating structure with a load of a watercolum of 300m if there had not been engineering examples on record where concrete has worked well under this kind of conditions.
The kölbrain sperre in the austrian alps for example.
Or all kind of submarine tunnel applications…
So stuff like troll A does not come from a “crazy inventor website” which claims “wonder materials” - but from a long and solid engineering traditon. That the public is mostly “unaware of”
But a serious engineer has studied before considering and designing anything like that.
The benefits and limits of the stuff that comes out of this foam generator needs to be known and tested before considering it for any kind of engineering…so even if it holds any bit of promis the inventor claims, serious engineering with the stuff starts 30 years of testing down the road…if the promises are kept…
Fiber laminates are here for a long long time in many applications - but the first airplane cabin built out of it is yet to come…
Construction technology that is valid and in widespread use as we speak…
To put the “established engineering of floating structures” into a single picture i would choose the picture above…
What you see here:
This is a floating wharf a piece of floating infrastructure for a harbor. It is standing in a drydock ( which is a big box with a removable door that can be filled with water to float the piece out )
So there is literally no signifficant difference to how you would build a bridge segment, the basement of building, a highrise, a tunnel, or another thing from the concrete engineers basic handbook.
On the left hand you see a staple of preformed segments which are there to be the closure on top of the cells.
In the context of your ring road it is also clear that this kind of honeycomb structure can get a 60 cm plate on top where traffic can take place and even a 60 ton tank can roll over it.
It also becomes inmediatly clear why you would definitly not fill this kind of hollow cells with styrofoam nor with a messy soap cement mixture…from the crazy inventors playbook. (doing messy stuff in that quantity and volume is just not feasible )
This is the kind of engineering that leading structural concrete engineer P.K.Metha refers to, when he says that “It is expected that 21st century will be dominated by concrete sea structures” in the preamble to his concrete engineering book.
It is the engineering of the | mullberry floating harbor | , | the monaco breakwater | , the valiant jetty, the rofomex barge, etc. etc.
If you compare the two photos you see that the triangular piece is is basicly a study how small can i make the P.K.Mehta concrete engineering and it will still work.
So it is not really about doing something “fundamentally different and unpoven” it is about changing the scale … but doing proven stuff…
As always the devil is in the details… questions arise
It is obvious how i do work a 30 cm concrete wall ( standard cast method ) but how do i make a wall that is only 4 millimeter thick ? - certainly the standard method of forming and pour in does not work here anymore…
If i have the rebar stick out in the big piece to connect the tension forces what size of fiber component connecting the tension forces do i work in the small piece ?
If the big piece can accomodate the “concrete code” rebar components need a 5 cm concrete cover to be protected against corrosion and avoid spalling
What is clear from the picture is that the weight per cubic meter build is less in the triangular honeycomb piece than in the " foam cast" …
It is also clear that the triangle is “closed cell” that will not suck up water - while the foam is not.
Finally it is not written in stone that a honeycomb structure needs to be a slab on the watersurface you can also build something like this:
And from this it is a not so big a step to build this …
So when i say the floating city is unsinkable and acting like a foamblock… it is not that i recommend to actually build big portions of the city from some kind of messy foam material.
It is rather that everything is a “honeycomb structure of some kind” with closed cells and each cell floats.
They don’t let water seep from one cell to another - just like the pebbles in the styrofoam block float on their own, and no matter how you break it and how many cells you popp - it will never sink.
This kind of unsinkability - that does not depend on watertight sections and doors closing allows
to postulate a floating city that needs no rescue boats …
The building of ships is honeycomb structure building.
Even a 200 m ship is ok with a wall thickness of the cells of only 8-14 mm
So when you compare that to the triangle piece the similiarity becomes obvious… compared to steel concrete is about 3 times lighter, many times cheaper, and several times less prone to seawater damage.
The honeycomb structure of the WHY yacht a project of Wally Hermes that is half way between floating island and yacht…
context | current engineering baseline for floating construction | condamine port extension | the normal land base concrete engineering applied on large scale for floating structures | straight forward applyable - no monsters lurking in the dark…
no weired dynamic effects created by waves - that normal concrete construction can not handle.
The topic of cellular container sized floating devices underpinning a street on the water was discussed…
The foto shows the “established engineering baseline” that was testet and worked well.
Context | engineering baseline | the floating road used on d-day to unload the ships in the mulberry harbor |
