At 04:16 PM 5/5/03 -0700, you wrote:
>Hi all,



>Translation: You can cast whatever you want out of this mix, so long as 
>you vibrate it adequately to remove air pockets according to the 
>intended purpose.  The section I am designing for my Lehman base will 
>weigh ~ 68 lbs at 36" length and will at least as stiff as any available 
>steel section (like I-beams or structural tubing) of the same weight. 
>If this proves to be adequately noise-free, it will be a very cheap 
>(cement and sand cost <$20) way to build very stiff structural members.

I tried casting a large table out of a very simular mix, for some holography
experiments, and had a lot of problems with flexure during the cure.

It finally settled down after a few months, but I still see some seasonal
flexure due to temperature and humidity diffrences.

I think that a pre-stressed approach would be a lot better, but of course,
it would remove a lot of the reasons for useing concrete to begin with.

The table was 4' by 8' by 3 1/2 inches thick...

For what it's worth,

Daryl
 
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