Hello ...
> Can you tell me what "portland stone" is?
There is a brief introduction to Portland stone at
http://www.weymouth.gov.uk/weymouth/portston.htm
and a longer study at
http://www.weymouth.gov.uk/case4inx.htm
Both are worth the click.
>Is this limestone used to make portland cement?
Any kind of limestone can be used. The stone is crushed
and mixed with a small proportion of clay, then fired in
a high temperature kiln. The clinker is then ground to a
fine powder and mixed with gypsum. The result is cement.
The process was invented in 1824 by a English stonemason
named Joseph Aspdin. He called it Portland cement
because he wanted a classy brand name - he claimed that
concrete made from the new cement looked like the expensive
Portland stone. An early exercise in consumer deception -
nobody was fooled, but the name stuck.
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