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'[EE]: advice on blowing bubbles'
2006\08\14@085814 by Gus S Calabrese

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I want to make a machine that recycles plastic,  grinds it up, heats it
and blows very thin wall bubbles to mix with concrete.
The advice I am looking for is .....
#1  What plastics are suitable
#2  suggestions on best size for bubbles
#3  Has anyone ever worked with a technology like this and if so,  
what happened ?

Gus S Calabrese
4337 Raleigh Street
Denver, CO
720 222 1309     303 908 7716 cell
adding "spam2006" bypasses my spam blocker.  Please place in the text  
or at the END of the subject line.
( i am hard to reach by phone )


2006\08\14@095806 by M. Adam Davis

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I'm afraid I'm not going to be a great deal of help, but I'll add what
little I know below:

On 8/14/06, Gus S Calabrese <spam_OUTgscTakeThisOuTspamomegadogs.com> wrote:
> I want to make a machine that recycles plastic,  grinds it up, heats it
> and blows very thin wall bubbles to mix with concrete.
> The advice I am looking for is .....
> #1  What plastics are suitable
> #2  suggestions on best size for bubbles

It depends on the application.  I imagine that certian applications
could support very large bubbles (several inches in diameter) but for
most floating concrete applications you need the concrete to maintain
a great degree of strength and rigidity, so very small bubbles (a few
mm in diameter and smaller) are the largest you might use.

If you use polymer strings to increase the strength of the concrete
you can get away with bigger bubbles.

I suspect very thin wall plastic bubbles will collapse during the
mixing process regardless of the size.  Also keep in mind that
concrete heats up as it mixes and cures, and in fact can get very hot
internally.

Concrete canoe builders typically use glass microspheres.  One such
composition is shown in this page:
http://www.concretecanoe.org/
(editorial - caution: ugly site!)

> #3  Has anyone ever worked with a technology like this and if so,
> what happened ?

No, but I've followed the various concrete canoe competitions at some
universities as well as the very interesting flexible concrete being
developed at places like the University of Michigan.  Before I saw
this picture and read the article I had never considered concrete to
be elastic:

http://www.umich.edu/news/index.html?Releases/2005/May05/r050405

I drive over that about once a week.

What's the application?

-Adam

2006\08\14@105025 by Martin K

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Companies that make paint balls, the kind shot out of an air-gun at
other people, form and cut half-spheres out of sheets of polyethylene.
These half-spheres are then heat-welded together. This all happens
faster than the eye can see, of course.
I'm not so sure that "blowing bubbles" would be the best method of
producing those plastic bubbles.
Another method may be extruding a continuous cylinder and cutting and
fusing the end of the cylinder into appropriate lengths. These envelopes
of plastic could then be loaded into a vacuum chamber - the air inside
would expand creating a sphere

The whole process of recycling plastic is complicated. The plastic has
to be washed several times, chopped up, heated, extruded into pellets,
mixed with virgin plastic, and used in whatever process you want
thereafter. It may be more beneficial to buy already-pelleted recycled
plastic.

Other thoughts:
Concrete containing expanded polystyrene (styrofoam) is already fairly
common.
Maybe you could just add some baking soda to your concrete? ;-)
--
Martin K

Gus S Calabrese wrote:
{Quote hidden}

2006\08\14@105533 by Alan B. Pearce

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>Concrete canoe builders typically use glass microspheres.
>One such composition is shown in this page:

Hmm, I have heard of people doing concrete yachts, spraying concrete on over
a wooden frame, but hadn't heard of the canoe before.

2006\08\14@111556 by Alan B. Pearce

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>Other thoughts:
>Concrete containing expanded polystyrene (styrofoam)
>is already fairly common.
>Maybe you could just add some baking soda to your concrete? ;-)

Well, I was thinking of ping pong balls ...

2006\08\14@131051 by Sebastien Bailard

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On Monday 14 August 2006 11:15, Alan B. Pearce wrote:
> >Other thoughts:
> >Concrete containing expanded polystyrene (styrofoam)
> >is already fairly common.
> >Maybe you could just add some baking soda to your concrete? ;-)
>
> Well, I was thinking of ping pong balls ...

You'd want to go with the commonly used plastics, say type 1 and type 2.
According to
en.wikipedia.org/wiki/Resin_identification_code
that means
Polyethylene Terephthalate and High-Density Polyethylene

If you should want to research the matter, I found this, via a google scholar
search on "concrete recycled plastic"
scholar.google.com/scholar?q=concrete%20recycled%20plastic&ie=UTF-8&oe=UTF-8&hl=en
I found this
md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=0249096EN&q=concrete+recycled+plastic&uid=787316424&setcookie=yes
and people citing them.
http://scholar.google.com/scholar?hl=en&lr=&cites=7401572125866703561

Regards,
-Sebastien Bailard

2006\08\14@170226 by Aaron

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Alan B. Pearce wrote:

{Quote hidden}

Eight years ago, or so, I worked for a company that made concrete
batching control systems.  Liquids called admixtures are often metered
to the batch to give the concrete various properties.  One common admix
was called 'air'.  My boss once said (joked?) that some lesser quality
plants just used dishsoap.

Aaron

2006\08\15@044504 by Howard Winter

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Alan,

On Mon, 14 Aug 2006 16:15:45 +0100, Alan B. Pearce wrote:

> >Other thoughts:
> >Concrete containing expanded polystyrene (styrofoam)
> >is already fairly common.
> >Maybe you could just add some baking soda to your concrete? ;-)
>
> Well, I was thinking of ping pong balls ...

Or just lay perforated plastic pipes at the bottom, and pump air in so that it bubbles up into the setting concrete - it works with Aero chocolate!  :-)

Cheers,


Howard Winter
St.Albans, England


2006\08\15@045033 by Howard Winter

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picon face
Aaron,

On Mon, 14 Aug 2006 17:02:19 -0400, Aaron wrote:

> Eight years ago, or so, I worked for a company that made concrete
> batching control systems.  Liquids called admixtures are often metered
> to the batch to give the concrete various properties.  One common admix
> was called 'air'.  My boss once said (joked?) that some lesser quality
> plants just used dishsoap.

Many years ago my father was doing some repairs to the house (repointing some brickwork, I think) and he added washing-up liquid to the mortar mix
- he said it was cheaper than "plasticiser" made specially for the job, and worked just as well!

Cheers,


Howard Winter
St.Albans, England


2006\08\15@100303 by Tony Smith

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> > >Other thoughts:
> > >Concrete containing expanded polystyrene (styrofoam) is already
> > >fairly common.
> > >Maybe you could just add some baking soda to your concrete? ;-)
> >
> > Well, I was thinking of ping pong balls ...
>
> Or just lay perforated plastic pipes at the bottom, and pump
> air in so that it bubbles up into the setting concrete - it
> works with Aero chocolate!  :-)
>
> Cheers,
>
> Howard Winter


I went to the Aero bar factory once.  Apparently they use a vacuum to get
the bubbles.  Same technique as getting air out of silicon molds, put it in
a vacuum, bubbles expand and pop.  Except with silicon you try not to get
too many bubbles in the mix in the first place.

Apparently the trick with Aero bars is getting the vacuum just right...
"Aero Bar" - now with 50% British air!

Tony

2006\08\15@104742 by Rich

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I am curious as to what pumping air into the concrete does.  I am getting
ready to pour some concrete.  Should I know about this before I start the
project?

{Original Message removed}

2006\08\15@113309 by Tony Smith

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> I am curious as to what pumping air into the concrete does.  
> I am getting ready to pour some concrete.  Should I know
> about this before I start the project?


Makes it weaker.  Vibrating or compacting it gets the air out.  If you're
just pouring a floor for a small shed I wouldn't worry about it too much.

When you see a pipe connected to a compressor or such stuck in the concrete,
that a vibrator.  It agitates the mix so the bubbles travel upwards.

On the other hand, very small bubbles are sometimes added to the mix to make
it handle frost better.  The name for this escapes me at the moment.

Tony

2006\08\15@121340 by Robert Ammerman

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> Another method may be extruding a continuous cylinder and cutting and
> fusing the end of the cylinder into appropriate lengths. These envelopes
> of plastic could then be loaded into a vacuum chamber - the air inside
> would expand creating a sphere

Or the process of creating the envelopes could be carried out under pressure
so that when they are returned to normal pressure they will expand.


2006\08\16@005532 by Denny Esterline

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> > I am curious as to what pumping air into the concrete does.  
> > I am getting ready to pour some concrete.  Should I know
> > about this before I start the project?
>
>
> Makes it weaker.  Vibrating or compacting it gets the air out.  If you're
> just pouring a floor for a small shed I wouldn't worry about it too much.
>
> When you see a pipe connected to a compressor or such stuck in the concrete,
> that a vibrator.  It agitates the mix so the bubbles travel upwards.
>
> On the other hand, very small bubbles are sometimes added to the mix to make
> it handle frost better.  The name for this escapes me at the moment.
>
> Tony

Air Entrainment. Pretty important for outdoor concrete in freezing climates.
http://en.wikipedia.org/wiki/Air_entrainment

-Denny


2006\08\16@015817 by Tony Smith

picon face
> > On the other hand, very small bubbles are sometimes added
> to the mix
> > to make it handle frost better.  The name for this escapes
> me at the moment.
> >
> > Tony
>
> Air Entrainment. Pretty important for outdoor concrete in
> freezing climates.
> http://en.wikipedia.org/wiki/Air_entrainment
>
> -Denny


Ah, that's it.  I used to live in an area where that was important.  I don't
like being cold.

Done since 1930!  Some of those old guys were pretty smart.

Tony

2006\08\16@042524 by Russell McMahon

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>> > On the other hand, very small bubbles are sometimes added
>> to the mix

>> Air Entrainment. Pretty important for outdoor concrete in
>> freezing climates.
>> http://en.wikipedia.org/wiki/Air_entrainment

> Ah, that's it.  I used to live in an area where that was important.
> I don't
> like being cold.
>
> Done since 1930!  Some of those old guys were pretty smart.

Done *again* since the late 1930's, when it was discovered by mistake.

Done, it would appear, *originally* by the Romans, possibly by
including blood or milk in the mix (!). Many Roman structures are
concrete based. They considered it to be an unworthy material for
display purposes and went to lengths to cover it with other materials.

Air void analysis of concrete using a flatbed scanner.
Goo discussion on what is required to make AE concrete frost
resistant.
MSc civil Thesis
Mentions Roman air entrained concrete.

                http://www.cee.mtu.edu/~krpeters/air_voids/thesis2001.pdf

The control of air in concrete
This monolog mentions the Roman method (foodscraps -> soap) but
portrays it as an accident - in all relevant concrete apparently.
Knowing the Romans just a little his explanation is highly suspect.

       http://www.lmcc.com/news/spring2004/spring2004-08.asp

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