[PSUBS-MAILIST] concrete testing

Wed Jan 3 22:10:22 EST 2018

Underwater habitat??!!  I would certainly appreciate it if you would toss a copy of the study my way when able, Hank.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Brian Cox via Personal_Submersibles
Sent: Wednesday, January 3, 2018 2:59 PM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] concrete testing

Sure Hank !    Don't need it this second , but good to know you have that !

Brian

--- personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org>  wrote:

From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> >
To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> >
Subject: Re: [PSUBS-MAILIST] concrete testing
Date: Wed, 3 Jan 2018 19:06:11 +0000 (UTC)

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 <mailto: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 <mailto:personal_submersibles at psubs.org>  wrote:

From: "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> >
To: personal_submersibles at psubs.org <mailto: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 <mailto: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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