[PSUBS-MAILIST] concrete

[swaters]

One thing if you do decide to try a sub made of concrete, is to be sure you cut tru holes with dimond or carbon rather than any kind of impaction device (hammer drill). Using a impaction weakens the integraty around the hole itself. If you do try this, let me know and I can get you all kinds of deals with dimond cutting materials through my business. We buy thousands of dollars of it every year :)
Thanks,
Scott Waters




Sent from my U.S. Cellular© SmartphoneJoe Perkel <josephperkel at yahoo.com> wrote:It seems to me that with reduced cost materials there is a tendency to go big and unwieldy. 
Wasn't that the case with that one fellows concrete sub yacht? It's on the bottom of a lake somewhere if I recall.


Joe

Sent from Yahoo Mail for iPad

From: Sean T. Stevenson <cast55 at telus.net>; 
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>; 
Subject: Re: [PSUBS-MAILIST] concrete 
Sent: Sun, Apr 13, 2014 6:16:35 AM 

I ran that same 6' diameter 4" shell, but using an ultra high-performace concrete with no aggregate, but with steel fiber reinforcement.  Working pressure came out to more than 1700 m.  That said, while the compressive strength of this stuff is 160 MPa, the tensile is only 8 MPa, so you absolutely have to avoid putting this stuff in tension.  Sphere may not be an issue, but a cylindrical hull would probably require some sort of pretensioned reinforcement.  Results:




On 2014-04-12 21:52, Marc de Piolenc wrote:
I had forgotten about the lubricant/plasticizer properties of fly ash. 

Marc 

On 4/13/2014 10:55 AM, hank pronk wrote: 
Marc, 
We don't get segregation at all, when pumping it we fill the wall and then let it flow, I call it "ride the wave" 
Also pumping the concrete helps hold the concrete together, it stays in a cylinder shape until it hits the wave. We must use fly ash because the aggregate and sand is washed so well there are no fines left.  The jagged sand won't flow through the hose.  Fly ash is like little ball bearings and makes it flow through the hose.  These are the things that make me think a mold  is the way to go.  Four inches wall thickness would be a breeze for this mix. 
That makes sense that the rock is a cheap filler.  I would still use the pea gravel mix, I have made a test panel and I drove my bob-cat over a 2in thick 4by4 panel with no breakage.  I know, very scientific .lol 

Hank 
-------------------------------------------- 
On Sat, 4/12/14, Marc de Piolenc <piolenc at archivale.com> wrote:         

  Subject: Re: [PSUBS-MAILIST] concrete 
  To: personal_submersibles at psubs.org 
  Received: Saturday, April 12, 2014, 10:40 PM 

  Actually, all else being equal, using 
  only fine aggregate (sand) will give a stronger mix. Coarse 
  aggregate is needed mainly to make the mix affordable - as 
  bulk filler, in other words - and also for decorative effect 
  in some applications where the fresh concrete is brushed to 
  show off the aggregate. 

  You have to be careful, in very high-strength applications, 
  to make sure that the coarse aggregate is chemically inert 
  with respect to the cement matrix. Some siliceous aggregate 
  will weaken the concrete in the long term by reacting slowly 
  with the matrix long after cure. 

  Confusingly, very fine silica incorporated in the form of 
  fly ash, rice husk ash or silica fume can give a 
  super-HIGH-strength mix. The reason for the effect is that 
  the very fine silica reacts with the alkali formed DURING 
  cure and actually strengthens the cement matrix. 
  Unfortunately, much of the fly-ash and volcanic ash cement 
  on the market is too coarsely ground to harness this 
  effect. 

  Best, 
  Marc de Piolenc 
  Ferrocement freak 

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