[PSUBS-MAILIST] concrete subs sealing filtering, cracks, special concrete

[diagroto@ibague.cetcol.net.co]

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to: personal_submersibles@psubs.org
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concrete subs sealing filtering, cracks, special concrete
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A question was:
> did you use special concrete in your sub ?

You can make Concrete waterproof with epoxy or acrylic sealants as dave irons 
explains in a message at: Sun, 14 Mar 1999 16:53:29 EST 
The company SIKA (specialized in concrete sealants) offers dozends of products 
for it.
I did not use that stuff in my sub.
A 3 mm tarmac based flexible skin (reinforced with glass fiber) as used to stop 
water in buildings and tunnels is more than sufficient.
To protect concrete wall against water filtering in. Worked perfectly.
If you believe that my approach to sealing (put tarmac silicon etc.. on it - it 
will hold) is too low tec,
remember story of TRIESTE they glued two steel half spheres together. Few days 
before deep dive
this broke due to termal expansion (two halves had different temperature when 
glued) water was comming in - some drops per minute - quite a leak fo a sub.
This was GUAM far from any high tec they had to fix it with what was on hand 
there. They put rubber band on it an paint it over with tarmac.
Imagine ! tecnically they had a CRACK going all the way trough their steel 
wall - and worse - water filtering trough already on surface. (micro crack or 
pores or bubbles in concrete is by far less problem)
 How would this crack behave under pressure of 11000 m of seawater ??!!
only seald with rubber and tarmac !!! (not even silicon was available at this 
time) would water come in with a force to cut steel and man in half ??? - i 
imagine they had sleepless nights on that problem.
We know it better, sleep well, they did the record deep dive with that - no 
drop came in.
So if you imagine a concret sub hull with micro cracks and pores, and have 
sleepless nights over the problem - i recommend you - think about trieste put 
tarmac on it and sleep well.
If it holds 11000m it will hold a couple of hundreds in your sub.
It did -perfectly- in mine.
I used normal concrete - normal steel bars - normal sealings - all as in normal 
construction sites.
(Where you have to deal with water and concrete under hydrostatic pressure 
every day)
No fancy experimental stuff.
Nothing else. - worked all perfectly

Wilfried Ellmer
(concrete sub diver - still alive - )