[PSUBS-MAILIST] concrete

[hank pronk]

I would make a mould and pour the concrete.  We pump concrete into Styrofoam forms all the time and they are plumb full of re-bar.  The local batch plant and I experimented to find a perfect mix.  They deliver a 4in slump 35mpa mix with 3/8 aggregate and lots of flyash.  When the truck arrives we add plasticizer to make the mix into a 6in slump,and it flows like water and does not plug up the 2in line.  The plasticizer lasts for 20 min and does not weaken the mix like adding water would.  Building a sphere mold would be easy peezy.
Hank 
--------------------------------------------
On Sat, 4/12/14, Sean T. Stevenson <cast55 at telus.net> wrote:

 Subject: Re: [PSUBS-MAILIST] concrete
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Saturday, April 12, 2014, 8:06 PM
 
 I wasn't thinking about fine mesh as
 in the sort of backing you would
 use as a shotcrete / gunnite form, but rather a large (e.g.
 3-4") wire
 mesh just to discourage cracking.  In any case,
 interesting about the
 reinforcement actually working against you.  I wouldn't
 have expected
 that, but then I know only enough about concrete to be
 dangerous. 
 ;-)    I had another thought - could you use two
 concentric steel
 spheres of relatively light gauge, that could be spun
 without too much
 regard for perfect roundness or shape control, as forms for
 your
 concrete, that would remain in place after the pour - the
 outer one
 serving as impact protection, and the inner one serving as a
 base to
 weld your interior fixtures to?
 
 Sean
 
 
 On 2014-04-12 17:13, Marc de Piolenc wrote:
 > Fiber-reinforced mortar is very difficult to apply to
 reinforcement
 > consisting of fine mesh. It's been a subject of
 discussion on the
 > Ferrocement forum for some time - people wanting the
 benefit of
 > distributed fiber reinforcement while retaining the
 advantage of
 > multiple layers of mesh - namely the ability to
 dispense completely
 > with molds.
 >
 > As for rebar, it has only one function in a ferrocement
 structure,
 > namely giving the bare armature enough stiffness and
 strength to hold
 > the weight of the uncured mortar without distortion. In
 the final
 > structure it actually causes stress concentrations. The
 US Navy
 > compared FC structures with and without rebar years ago
 and the latter
 > won hands down in terms of structural efficiency and
 durability.
 >
 > If you have a mold - male or female - you don't need
 the rebar. Plain
 > mesh works just fine. Martin Iorns' laminated
 ferrocement technique
 > also works just fine. In that technique, instead of
 forcing mortar
 > into multiple layers of mesh, mesh and mortar layers
 are applied in
 > alternation. And if you have fiber-reinforced mortar
 and some way to
 > hold it in place while curing, you don't need mesh
 (though you can
 > still use it, with Iorns' technique)!
 >
 > But with FC we're not talking about pouring the matrix
 - the panels
 > are too thin to do that reliably, vibrator or no
 vibrator. Instead,
 > plastering technique has to be used. This is not
 entirely a bad thing,
 > since it allows half the mold to be dispensed with and
 gives the
 > applicators a good view of their work, so that they can
 catch voids
 > and sand pockets in the making and correct them.
 >
 > Marc
 >
 > On 4/12/2014 9:37 PM, Sean T. Stevenson wrote:
 >> Build a geodesic dome out of rebar, cover it in
 mesh, and pour a sphere
 >> of ultra high strength (no aggregate) fiber
 reinforced concrete around
 >> it, vibrating the hell out of it to eliminate
 bubbles. The shape might
 >> be a bit strange, given that your openings need be
 reinforced with a pad
 >> sufficent to replace the material missing in the
 opening, and your
 >> concrete shell is quite thick. You'd have to build
 a bunch of them,
 >> strain gauge them all, and lower them over the side
 until failure.
 >>
 >> Sean
 >>
 >>
 >>
 >> On April 12, 2014 6:40:53 AM MDT, hank pronk <hanker_20032000 at yahoo.ca>
 >> wrote:
 >>
 >>     Hi Sean,
 >>     Thank you for the
 calculation. That figure is quite interesting,
 >> considering it is only 30mpa.  I wonder if
 re-enforcement is
 >> beneficial given the sphere shape.
 >>     Imagine if you could figure
 out a safe way to make an opening in
 >> the sphere for ports and hatch, you could build a
 hull for under
 >> 1,000 dollars.  Amazing!
 >>     Hank
 >>    
 >>
 ------------------------------------------------------------------------
 >>
 >>     On Fri, 4/11/14, Sean T.
 Stevenson <cast55 at telus.net>
 wrote:
 >>
 >>       Subject: Re:
 [PSUBS-MAILIST] concrete
 >>       To: "Personal
 Submersibles General Discussion"
 >> <personal_submersibles at psubs.org>
 >>       Received: Friday,
 April 11, 2014, 10:34 PM
 >>
 >>
 >>
 >>
 >>
 >>
 >>
 >>           Hank,
 >>
 >>
 >>
 >>         
    There are countless varieties of concrete,
 all with
 >>       different
 >>         
    mechanical properties, so it is difficult
 to make an
 >>       effective
 >>         
    comparison, but just for fun, I ran your
 scenario
 >>       (6' OD, 4in
 >>
 >>     thick shell) with average
 material properties for
 >>       ordinary
 >>         
    concrete, and it turns out it's good to
 over 1000
 >>       fsw!  See
 below.
 >>
 >>
 >>
 >>         
    Sean
 
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