by John Carter

Created on: June 02, 2007

This is the kind of cement that was used by the ancient Romans although there is evidence that it predates the days of Rome. The largest free standing dome in the world is found in the Roman building known as Hadrian's Tomb. This building was built almost two thousand years ago. Like a lot of Roman architecture one is unable to determine its true age by looking this is a testimony to the Romans building methods.

Pozzolanic cement is made by mixing quicklime with finely ground volcanic pumice or ash. After the lime and pumice have reacted the cement is thoroughly mixed with a mixture of sand and crushed stone. This changes it from cement into concrete that like modern Portland cement will set under water. It is used wherever you would use modern concrete.

The Roman's made a kind of lightweight concrete by mixing into the mix as they went along small sealed ceramic bottles. This was used in many places that are the same as modern lightweight concrete. A notable example of this was in Hadrian's Tomb or the Coliseum.

Mortar used in masonry was made using a different formulation in this case instead of using pumice they substituted a finely ground material made from broken bricks or ceramics. This was used to bind the stones or other building material together. Good examples of this are some of the Roman Aqueducts that are still standing today.

A modern variation of some of the Roman building techniques can be found all over the world where cement material is intimately mixed with subsoil to form an in-situ concrete that forms when the cement sets. This is normally used by the simple expedient of plowing it into the soil with a harrow.

One of the places where there is a lot of raw material for making Pozzolanic cement is in the Caribbean Sea in the islands surrounding Montserrat. The volcano there has made a gift of millions of tons of volcanic ash that if mixed with quicklime would make a useful cement.

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