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"Roman cement"
was developed by James Parker in the 1780s, and finally
patented in 1796.
It was, in fact, nothing
like any material used by the Romans, but was a “Natural cement"
made by burning septaria - nodules that are found in certain clay deposits,
and that contain both clay minerals and calcium carbonate. The burnt nodules
were ground to a fine powder. This product, made into a mortar with sand, set
in 5-15 minutes.
The success of "Roman Cement" led other manufacturers to develop
rival products by burning artificial mixtures of clay and chalk.
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