Comment 72283

By GerryM (registered) | Posted December 14, 2011 at 20:55:48

I am no expert on cement -- it is now a highly technical subject and the experts are mainly civil or chemical engineers. There is, however, an excellent Wikipedia article which gives the history and references to technical details.

In the Mediterranean, the Romans and others used a cement made by mixing lime with volcanic ash (called pozzolana). Portland cement generally used lime and an inert mix, such as sand. Other materials can be used instead of sand, which do react chemically. Some forms of limestone ("cement rock" -- including one bed that was mined near Niagara Falls) can be burned to form a lime which acts as a cement without additives, because the limestone itself contained substantial amounts of clay.

When the first canals and lighthouses were built in the UK (and soon after in the USA and Canada) the ancient techniques used by the Romans were re-discovered, as it was necessary to produce a "hydraulic cement" that would set quickly, and under water. In fact, the beginning of civil engineering in the US dates from the construction of the Erie Canal.

I doubt that the best modern cements weather any faster than natural stone -- but, as I have written, I am no expert!

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