Hydraulic setting cements were first developed by the Greeks and Romans. These cements exhibit an increase in strength when stored under water after setting. They were made by the addition of volcanic ash (pozzolana) to the slaked lime and sand to produce a mortar which possessed superior strength when compared with the lime/sand mixture and when set was resistant to the action of water. (The original volcanic ash used as a pozzolanic material was produced by two violent volcanic eruptions in the Mediterranean, the first being in the Aegean island of Thera, now known as Santorin in Greece, and the second in a d 79 when Mt Vesuvius erupted on the bay of Naples in Italy (ACI Committee 232 Report, 1994).) The pozzolana-lime mixture was discovered by the Greeks sometime between 700 and 600 b c , this was later passed on to the Romans who used it in mortar and concrete in about 150 b c (Kirby et al., 1956, p. 63). Pozzolanic cement mortar which has lasted over the centuries was used in the construction of the Colosseum in Rome (Drysdale et al., 1994). The hydraulic cement produced from this material is known as ‘Roman’ cement.