Re: Concrete reinforcement

[Rick Lucertini <empiricus@sprint.ca>]

Hi, Dave and All   . . .

DaveIrons@aol.com wrote:

> [snip]     River rock seems like a
> poor choice.  River rock is a mixture of rock types, some of which may
> weaken the concrete mix.  The irregular shape of crushed stone seems to
> enhance the bonding between the concrete and aggregate.

I feel the same way.  The ellipsoid shapes of river rocks would encourage slipping of
the concrete along the surface of the stones.  Irregular and rough stone would result
in greater bonding and minimal slippage.

Then again . . .

> I would
> recommend that test samples should be made and tested to destruction.

Concrete is certainly cheap enough to test out a few hulls.

> Adding polymer (PIC) in place of water produces a 20,000 psi pressure
> hull.  The depth rating increases to 4,000 feet.

Sorry, what hull thickness?  I think you mentioned that in a previous post.  Must
thave missed it.

> Polymer-Impregnated Concrete (PIC) has a tensile strength of 1,600 psi.
> The durability of PIC is better than concrete.  It is more resistant to
> chemical attack and it is impermeable to water.

How much more expensive is it?

> Although concrete is waterproof prolonged immersion in water saturates
> the concrete and reduces the strength by about 10%.

I wonder if there would be any seawater weeping through the inner wall . . .

>   The ideal hull would be of steel
> sandwich construction. [snip]    I would like to include a few design ideas for
> further discussion.

Please, let's hear them.  This is a fascinating thread.

> Placing steel reinforcement on the outside of the hull makes sense.  The
> bending stress of the hull would be greatest at the outside surface of the
> hull.  For example: The hull is cylindrical with hemisphere end caps.
> Steel cables are stretched from bow to stern.  The cables are pretensioned
> using a 100,000 pound hydraulic bottle jack.  The cables are welded to
> steel bands at the bow and stern.  Steel cables are stretched around the
> circumference of the hull.  The cables are pretensioned and welded into
> place.  A seacrete shell (Sea Water Electrolytic Mineral Accretion) would
> be grown around the cables to bond them permanently to the hull and to
> protect them from corrosion.  The method is similar to standard
> pretensioned concrete construction except that the steel cables would
> ordinarily be placed inside a concrete slab.

I wondered how you would apply pre-tensioning.

I wonder if polymers could somehow be introduced to Wolf Hilbert's Seacrete?  There's
a technical challenge.


Rick


--
Rick Lucertini
empiricus@sprint.ca
(Vancouver, Canada)