[ARC5] cement

[Kenneth G. Gordon]

On 16 Oct 2012 at 7:28, gordon white wrote:

>     Marble ( in statues) is essentially metamorphosed limestone.
> Portland cement is limestone, ground up and heated.

Just in case this is not well known here, the "secret" of Roman-made 
waterproof cement was lost for many centuries until some French-man did 
considerable research on it sometime in the mid to late 1800s, and finally 
arrived at pretty much the formula we use today.

Ken W7EKB