ATM Concrete moulds could be DANGEROUS

["Peter John Smith" <pjifl@bigpond.com>]

From: Dominic-Luc Webb wrote :-


>>>
also find that concrete works in a lot
more applications than just a mount or counterweights. You
could for instance use concrete to make molds and pour
aluminum, etc.
>>>

Pouring molten Al in a concrete mould can be VERY DANGEROUS.

If the concrete is of normal mix the mould has a very high chance of
exploding violently showering you with molten Al.

On the other hand, if a coarse sand is mixed with a very small amount of
cement powder and the cured product dried well it can work quite well.  This
is probably what is intended.

The critical factor is that the final product must be porous, permeable to
gases, and able to be well dried.

I think somewhere between 1 % to 5 % cement powder in coarse sand is about
right but it may be even less.  Do more research on this before trying it.
You want enough cement to just stop the mould from crumbling when it is
carefully handled.

Of course some other material like a small amount of clay can be added in
place of the cement which is what I have used.

Peter Smith.