Surely we know all about cement – don't we?

AbstractPlaster, cement and concrete have been used since antiquity, notably by the Romans. Portland cement was patented by Joseph Aspdin of Leeds in 1824. Since then it has been gradually refined to become the fundamental constituent of modern concrete, familiar to all of us as the major construction material of the past century. Contemporary constructions such as skyscrapers, concert halls, suspension bridges and huge dams testify to the successful use of Portland cement concrete. For routine constructions its compressive strength development and durability are sufficiently well understood for it to be used with confidence in many diverse situations and in locations with widely different climate conditions. Even in the last 30 years, however, unexpected durability problems, such as the alkali silica reaction (ASR), delayed ettringite formation (DEF) and the thaumasite form of sulphate attack (TSA), have emerged. To ensure that the civil engineer can take the necessary steps to avoid their occurrence has required the methods of materials science to be applied to understand the mechanism of these processes. Recent ideas pertaining to the reaction mechanisms underlying DEF and TSA are critically reviewed.Keywords: JOSEPH MELLORCEMENT CHEMISTRYCONCRETEDELAYED ETTRINGITE FORMATIONTHAUMASITE SULPHATE ATTACK