[PSUBS-MAILIST] concrete
Marc de Piolenc
piolenc at archivale.com
Sat Apr 12 22:40:58 EDT 2014
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
On 4/13/2014 8:58 AM, hank pronk wrote:
> Marc,
> If I am not mistaken, the strongest concrete mix uses 3/4in fractured rock with sand, Portland and water. I would think a sand mix without rock would not be as strong. Also think of the skill you would need to trowel a sphere. Anyways it is pretty crazy what Sean has shown us with the calculations.
> 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, 5:58 AM
>
> I never thought of it quite that way.
> Sheesh, that makes concrete boat
> advocacy look almost...well, normal.
>
> Marc
>
> On 4/12/2014 2:21 PM, Alan James wrote:
> > Marc,
> >>>Right now I feel like I'm one of a tiny deviant
> cult .......
> > Well you are an American of
> French heritage hiding away on an obscure
> > seldom visited South East Asian Island populated by man
> hungry women
> > & Moslem rebels.
> > Alan
> >
> >
> ------------------------------------------------------------------------
> > *From:* Marc de Piolenc <piolenc at archivale.com>
> > *To:* personal_submersibles at psubs.org
> > *Sent:* Saturday, April 12, 2014 1:42 PM
> > *Subject:* Re: [PSUBS-MAILIST] concrete
> >
> > I think I will post those reports to Dropbox.
> >
> > Right now I feel like I'm one of a tiny deviant cult of
> Portland cement
> > cultists within the psubs community. Maybe the reports
> will help me
> > proselytize new adherents...
> >
> > Marc
> >
> > On 4/12/2014 9:03 AM, hank pronk wrote:
> > > Marc,
> > > Not only is it dirt cheap, concrete is so
> easy to form. The material
> > cost for a 6 foot sphere is in the hundreds, not
> thousands. Hank
> > >
> --------------------------------------------
> > > On Fri, 4/11/14, Marc de Piolenc <piolenc at archivale.com
> > <mailto:piolenc at archivale.com>>
> wrote:
> > >
> > > Subject: Re: [PSUBS-MAILIST] concrete
> > > To: "Personal Submersibles General
> Discussion"
> > <personal_submersibles at psubs.org
> <mailto:personal_submersibles at psubs.org>>
> > > Received: Friday, April 11, 2014, 8:26
> PM
> > >
> > > I don't have hard numbers, but
> > > remember that resistance to mostly
> > > compressive loading is a structural
> STABILITY problem. Most
> > > practical
> > > steel structures buckle under
> compression long before
> > > reaching their
> > > actual compression limit. Concrete has
> an advantage there
> > > due to its
> > > stiffness - the NCEL tests suggest
> that it comes much closer
> > > to using
> > > its full compressive strength.
> > >
> > > That said, my primary interest in
> concrete is due to its
> > > cost and ease
> > > of maintenance.
> > >
> > > Marc
> > >
> > > PS. If anybody is interested, I will
> add the relevant
> > > reports that I
> > > have to my public Dropbox folder and
> post the link.
> > >
> > > On 4/12/2014 3:15 AM, hank pronk
> wrote:
> > > > A six foot od sphere built in
> 1.25in thick steel would
> > > be equal in weight to 4in thick
> concrete. I would not
> > > ever expect 4in concrete to compare to
> 1.25 steel.
> > > But, it would be interesting to know
> where the concrete
> > > stands in comparison.
> > > > Hank
> > > >
> --------------------------------------------
> > > > On Fri, 4/11/14, Marc de Piolenc
> <piolenc at archivale.com
> > <mailto:piolenc at archivale.com>>
> > > wrote:
> > > >
> > > > Subject: Re:
> [PSUBS-MAILIST] concrete
> > > > To: "Personal Submersibles
> General
> > > Discussion" <personal_submersibles at psubs.org
> > <mailto:personal_submersibles at psubs.org>>
> > > > Received: Friday, April 11,
> 2014, 9:59
> > > AM
> > > >
> > > > A huge amount of work was
> done on
> > > > concrete for
> pressure-resisting
> > > structures, including long
> > > > term, deep exposure tests,
> by the US
> > > Naval Civil Engineering
> > > > Laboratory. Most of the
> reports are
> > > available for
> > > > downloading free of charge
> from DTIC.
> > > >
> > > > Excellent results were
> achieved with
> > > concrete having NO
> > > > reinforcement. There has
> been limited
> > > work done with
> > > > prestressed concrete and
> even less
> > > done with reinforced
> > > > concrete and ferrocement,
> which can
> > > reasonably be expected
> > > > to give much more efficient
> and
> > > distortion-tolerant
> > > > structures.
> > > >
> > > > Marc
> > > >
> > > > On 4/11/2014 8:25 PM, hank
> pronk
> > > wrote:
> > > > > A cheap alternative to
> a super
> > > strong sphere hull is
> > > > re-enforced concrete. I
> feel like
> > > hiding under a blanket
> > > > while I say this,lol.
> I know it
> > > is way out there, but
> > > > concrete is super strong
> under
> > > compression. It is not
> > > > so good for impact
> resistance.
> > > Concrete is a very easy
> > > > material to work with and
> form into a
> > > sphere shape. I
> > > > have no idea what thickness
> would be
> > > needed. Properly
> > > > engineered I would trust
> it.
> > > > > Hank
> > > > >
> > > > >
> > >
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