[PSUBS-MAILIST] concrete testing

Wed Jan 3 22:32:45 EST 2018

I'd be interested in a copy of that, too... Is it in digital form?

Marc de Piolenc

On 1/4/2018 3:06 AM, hank pronk via Personal_Submersibles wrote:
> Brian,
> If your interested in an underwater habitat made from concrete, I can 
> send you a study on concrete spheres done off the California coast over 
> 20 years if memory serves?  You can make a buoyant concrete sphere for 
> well over 1,000 feet.
> Hank
> 
> On Wednesday, January 3, 2018, 9:46:02 AM MST, Brian Cox via 
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Hi Sean,
>            The thought of testing occurred to me after I cut out five 
> access holes from the bottom of my ferro-cement hull .  I had to do this 
> to better seal the joint which runs horizontally joining the two halves 
> of the hull.  The construction of the hull has 3" ribs every 18" , those 
> were set up first and then stringers of 5/16ths (hot rolled) were run 
> connecting all the ribs, then diagonals, using spring wire ( about 1/8th 
> inch, to keep shape) were run in opposing directions.  Then after that 4 
> layers of 1/2" aviary hex wire was tied to each side for a total of 8 
> layers of wire. So there's a mass of metal in there !   I used a 2 to 1 
> sand to cement ratio , and I used a gradient sand mix that was produce 
> from a rock quarry . so a very hard material with jagged edges .  The 
> distribution of fines to coarse sand turned out to be a almost prefect 
> match to what was required.  So the actual hull that I have is stronger 
> since I have those ribs every 18", but the samples I have from cutting 
> out the access holes are just in between the ribs and would not 
> represent the overall hull.   I thought it would be interesting to see 
> what kind of strength the concrete has for someday making a pressure 
> hull for a shallow habitat .    The pieces I have are 12" x 16" x 1 1/2" .
> Brian
> 
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: "Sean T. Stevenson via Personal_Submersibles" 
> <personal_submersibles at psubs.org>
> To: personal_submersibles at psubs.org
> Subject: Re: [PSUBS-MAILIST] concrete testing
> Date: Wed, 03 Jan 2018 10:52:24 -0500
> 
> Hey Brian - Just catching up on weeks of email after a prolonged absence.
> 
> There are tests that you can do to concrete samples to establish their 
> strength, but generally these are samples which are cast in a particular 
> shape and cured to specification to validate the composition and cure of 
> an intended pour. Anything can be tested, but you're really talking 
> about a unique test for an already fabricated part, in which case the 
> the test is not to an established protocol but rather tailored to what 
> you want to get out of it. I could quote some testing for you, but I 
> suspect that the quote will not be in the same order of magnitude that 
> you're looking for. Do you know exactly what you're trying to determine?
> 
> Concrete is much stronger in compression than it is in tension, which is 
> why we use steel reinforcement in concrete structures, and why 
> "pre-tensioning" is a thing (actually pre-compressing the concrete, and 
> tensioning the steel members, so that as a concrete beam is subject to 
> tension, it actually is just reducing the compressive force but is still 
> in compression). Concrete designs should strive to load concrete in pure 
> compression and minimize tensional, torsional, and bending loads 
> wherever possible.
> 
> What is your ferrocement layup?
> 
> Sean
> 
> -------- Original Message --------
> On Dec 24, 2017, 20:28, Brian Cox via Personal_Submersibles < 
> personal_submersibles at psubs.org> wrote:
> 
> 
>     Hey Sean,
>                                I have a number of sections of my ferro
>     -cement hull  ( 12" x 16"  x 1 1/2")   .  Is there anyway to have a
>     strength test done on these?   I don't know if the test could be
>     extrapolated to larger sections or not .   Also I have ribs within
>     the structure at 18" intervals so obviously it would not account for
>     that.  I have the sections because I cut out access holes to enable
>     me to better seal the inside.
>     Brian
> 
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