1.1 Introduction

Cementitious materials are certainly the oldest manufactured materials of construction, and today are the predominant construction materials worldwide, their production far outstripping those of steel, timber, asphalt and other building materials. Their use goes back at least 9000 years, as in a mortar floor discovered in Israel (Malinowski and Garfinkel 1991; Bentur 2002). Similar lime mortars, prepared by calcining limestone, were used throughout the Middle East. Gypsum-based mortars were later used in Egypt, for example in the construction of the Pyramid of Cheops (~3000 B.C.); these were prepared by calcining impure gypsum. However, neither of these cementing materials is hydraulic; that is, they will not harden under water.

Later, the Greeks and the Romans were able to produce hydraulic lime mortars, mixed with finely ground volcanic ash. In particular, the Romans used a material called pozzolana, found in the vicinity of the village of Pozzuoli, near Mt Vesuvius. This material is described by Vitruvius ^[1] writing in about 27 B.C.:

• There is also a kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of Baiea and in the country belonging to the towns round about Mt Vesuvius. This substance, when mixed with lime and rubble, not only lends strength to buildings of other kinds, but even when piers of it are constructed in the sea, they set hard under water.

Materials such as these were used extensively in hydraulic structures, such as...