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 
http://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"
http://scholar.google.com/scholar?q=concrete%20recycled%20plastic&ie=UTF-8&oe=UTF-8&hl=en
I found this 
http://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
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