Reinforced Ferrocement and Acrylic mix question.

Discussion in 'Boat Design' started by Boucaneer, Oct 21, 2014.

  1. Boucaneer
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    Boucaneer Junior Member

    Hello chaps,

    I am planning to build a hexagonal reinforced ferrocement concrete floating island 8-12 feet wide. The individual islands can be connected together and form an island of fair size and shape in different configurations to adapt to the space and shoreline on the rivers and lakes in South Asia.

    I am from London, England myself and plan to build them in South India.

    The question I have is about the acrylic mixture to help with the elasticity and waterproofing of the ferrocement, in fact any information about the ferrocement procedure would be a great thing to receive.

    I trained as a waterman on the River Thames and help with the Thames Auxiliary Marine Service.

    Please, I am wondering what is the best Acrylic additive to buy and mix with my ferrocement and how much.

    Also any tips about reinforced ferrocement would be much appreciated.

    Wishing you all well.

    Thanks, Alex.
     
  2. philSweet
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    philSweet Senior Member

    You don't need any. And you don't need ferrocement. You need quality control and a reasonably good quality portland cement and properly graded aggregates. What is the thinnest section of concrete and are you just pouring around Styrofoam? What size rebar and wire mesh are in the thin sections?

    Buy a concrete engineering handbook. It's not that difficult a subject. Once you start connecting a few of them together, though, it begins to get interesting.

    Transportation? Weight and size and launch procedure?

    Modular concrete floating docks have been around for a long time.
     
  3. Boucaneer
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    Boucaneer Junior Member

    Thank you Phil,

    Any suggestion's for a good concrete engineering handbook?

    I thought Portland cement mixed with sand was ferrocement.

    I plan to use basic galvanised chicken wire and not pouring the cement, I am troweling a quarter inch layer then pushing and sinking the chicken wire in the cement layer, then another quarter inch thick layer of cement and another layer of wire mesh, then once more with another 1/4 " cement lamination and chicken wire. So maybe 3/4 three quarters of an inch thick in the laminated reinforced concrete.

    Didn't plan on using rebar. Just simple chicken wire.

    Transportation, pick up and stick on the back of a flat bed or pick up truck.

    I want the 12 foot hexagons to be hand launch with two men and a launching ramp down into a lake.

    Trying to keep it as basic and simple a possible.

    I'm sure it will get interesting.

    Any suggestions?

    Thanks.
     
  4. JSL
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    JSL Senior Member

    years ago I worked with a fellow using Ferro Cement. From what I remember:
    Type 5 Portland cement with a 2:1 mix with sand and some pozzalith. Must pass a slump test (forget the numbers) but the mix is not that fluid and must be trowelled /vibrated into the armature.
    If weight is not a real issue, for docks you could probably just go with a good quality mix and do up reinforced concrete. A local firm CeFer Designs (no longer in business) built hundreds of docks.
    Water proofing the FC is not really necessary but if you do get weeping in concrete the best sealer is Xypex since it works best on wet concrete.
    John Samson wrote some books, also Bruce Bingham. The only outfit I know of still doing FC is Hartley in New Zealand.
     
  5. philSweet
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    philSweet Senior Member

    How do you link these things together? how do you attach to the concrete pilings. Go look at concrete docks, and buy a 10 ton crane. About 4 yards of concrete and 1 ton of steel reinforcing and fixtures should about do it (12 footer). That's about one man day for mold work each one, two hours in the rebar shop, and a about six man hours for the pour and cover and getting the cure going. You can pop them out like muffins. four guys, five molds, you're making 10 per week. You'll need about 5 acres of land.

    You might enjoy this -

    http://www.fs.fed.us/t-d/pubs/ppt_html/htm04232P01/slide11.htm
     
  6. Jeremy Harris
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    Jeremy Harris Senior Member

    I remember helping to plaster a ferrocement fishing boat around 35 years ago. The key thing was that the whole boat had to be plastered in a single day, as the whole hull has to be cured as a single entity. Wet cement doesn't chemically bond to cured cement, so doing it in layers doesn't work unless all the layers are laid up before the cement starts to cure. There were around a dozen of us, working flat out to get the hull plastered, with some inside (the hull was upside down) and some outside working from scafolding.

    Those inside were pushing out against those plastering the outside, to make sure that the whole armature was completely filled.

    The mix was a cement-rich Portland cement and sand mix, without any additives, I think. We did have to drape wet sacking over the finished bits of the hull to prevent it drying out, but the boat turned out well in the end. For a one-off self-built working boat I thought that ferrocement was a pretty good option, and the finished boat turned out well and was still working 20 odd years later with very little sign of wear and tear (unlike her steel hulled contemporaries that were all looking pretty scruffy).
     
  7. Boucaneer
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    Boucaneer Junior Member

    Great, Thank you Jeremy, Phil and JSL.

    Well before the floating islands in South Asia, while I am in England I will make a Sampan stern oar boat with the polystyrene/styrofoam and Portland cement mix. It will be a practise for the small islands making a 16 foot by 4 foot sampan which can be slept on in an emergancy.

    So, to render it up in one day doesn't seem too bad. Can I just confirm how you meant " unless laid up " please Jeremy.

    Does it mean still damp enough to take the second bond and not fully dry?

    I will put two laminations of chicken wire and Portland/sand mix on the Sampan boat. I think I will fully wrap the shaped polystyrene/styrofoam with chicken wire and fix the first layer of chicken wire with a type of nail/staples to hold the wire down and stop raised wire to keep a thin first coat.

    Or does laid up mean put on blocks so the underside of the flat hull can be rendered at the same time as the topside?

    I can do it that way too, my problem is then the second layer. Maybe I can apply the second layer of chicken wire to the not fully cured first layer of Portland cement and then apply the second coat before the first coat has dried.

    Would any of the above sound correct?

    I'm still learning so certainly not going into mass construction, its just a small project for me to enjoy in life.

    I think India would kick me out if I started building 100's of floating islands. :)

    I do like the simplicity of the Sampan also, stern oared propelled with a specialy made Yuhol oar which is quite efficient or maybe even an electric trolling motor in the future.

    It would be great to hear of any suggestion to help with the cementing and construction process. I'm picking it up bit by bit.

    I do enjoy the freedom to build your own boat and home, it seems very rewarding with a sense of accomplishment more so than putting up a set of shelves. :)

    Thank you for the above replies, it's certainly got this project started.
     
  8. Jeremy Harris
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    Jeremy Harris Senior Member

    I meant that you have to ensure that all the cement hasn't started curing. You can't plaster ferro in layers, you have to do it as one thickness in one go, with a lot of attention paid to making sure there are no voids.

    It's quite a manual process, as the mix needs to be pretty stiff, so the only way to get it into every nook and cranny is with force, hence the reason we had two plastering teams, one inside and one out, with each working with the other to squeeze the cement from both sides and ensure there were no internal voids.

    Another tip - get everyone to wear gloves, as the high cement content in the mix does nasty stuff to your skin. Your plasterers will end up using their hands to force the cement into awkward spots; somehow hands are far better tools than trowels when applying the stuff to the armature, trowels are only really needed to smooth and fair the faces.
     
  9. Boucaneer
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    Boucaneer Junior Member

    Yes, no voids or air traps. We will use a spatter coat technique, my flat mate is a plasterer. So if the ferrocement is still wet we can add another coat then?

    I understand that voids will trap water and cause rust and weaken the structure.

    Thanks for explaining what you meant.
     
  10. fredrosse
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    fredrosse USACE Steam

    Did a Senior Project evaluating ferrocement structures for marine use. The "ferro" part of the name stands for "Fe, or Iron" Much higher percentage of steel in the structure than most concrete structures. About 5% of the cross section is steel.

    One advantage is that, kept wet, cement expands somewhat, so there will be no shrinkage cracks forming if the hull is kept moist. If it really dries out, the shrinkage cracks we have all seen will show up.

    I remember the study concluded about 3/4 inch thickness, suitable for a 36 - 40 foot hull, and 1-1/2 inch thickness suitable for an 80 - 100 foot hull. Reinforcing mesh is welded wire mesh, with inside and outside coverings of galvanized expanded metal mesh, all wired to a welded trusswork of ordinary steel reinforcing bars.

    The US Govt sponsored the building of several ferrocement 45 foot fishing boats as aid to Jamaca in the early 1970's. The US Govt has full reports of their construction available on the internet.
     
  11. Boucaneer
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    Boucaneer Junior Member

    In fact, I have just been researching and I may use Geopolymer cement as it can have stronger properties than ordinary Portland cement.

    Still looking into it, just trying to glean as much information as possible to help me with this project.
     
  12. Boucaneer
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    Boucaneer Junior Member

    Great information, Thank you Fred Rosse.

    Yes, I am learning that I will have to keep the ferroconcrete covered with damp sheets to aid the curing process to prevent cracking. This ferroconcrete can keep getting stronger for up to a year. But may take up to a couple of weeks curing untill ready to launch.

    The Geopolymer can be a little quicker in around 5 days curing and could be stronger and lamination may be easier.
    Now I have to research calcium hydroxide, as it's used to cure the fly ash with with Portland cement.

    Apparently it came from the Romans using volcanic ash to build their bridges and underwater components.
    I like the fact old and new technology can go hand in hand with each other.

    Old P.P.C and new electric motor propulsion. Best of both worlds. :)
     
  13. Jeremy Harris
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    Jeremy Harris Senior Member

    I'll say it again - you cannot make up a ferro hull in layers, or laminates, as they simply will not bond to each other. The only bond between layers of cement where wet is added to partially cured is mechanical, and the first time the hull is stressed one or more layers will de-laminate.

    The hull HAS to be laid up as a single entity, with the whole hull thickness being made in one go.

    If the hull is too big to be completed in the cure time, then a plastering plan has to be worked out where the team starts at one end and works continuously around the clock towards the other end, with the finishing team working along behind them, so that the "wet edge" is maintained throughout the thickness of the hull. Adding retarders to the mix to slow down the cure is another possible option, but I'd want to be absolutely convinced that the retarder didn't significantly effect the strength of shrinkage of the cement..
     
  14. WindRaf
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    WindRaf Senior Member


  15. Boucaneer
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    Boucaneer Junior Member

    Thank you Jeremy, understood.

    Yes, I think the plan now is to then to trowel the ferrocement onto the first layer of mesh againts the styrofoam former using a splatter technique to aviod voids to around 3/4 inch then then push and sink a second layer of mesh into the wet ferrocement and pin and anchor with nail staples and the smooth and work the finish while wet.

    Thanks for explaining again Jeremy. I am clear on that now.

    Cheers.
     
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