Roman Cements: Key Materials of the Built Heritage of the 19th Century

Abstract

Highly hydraulic binders, known as natural or Roman cements, were key materials for the economic and easy manufacture of stuccoes for the exterior of buildings during the 19th and early 20th centuries. Roman cements were produced by burning naturally occurring deposits of calcium carbonate rich in clay minerals. They were distinguished from other hydraulic binders principally by a very short setting time, agreeable texture and colour, little shrinkage on setting and excellent weatherresistance. They were first produced in England in 1796 when James Parker patented a cement known as Parker's or Roman cement (Parker 1796 ). The material was obtained by firing clay-bearing calcareous nodules found in the London clay beds on the Isle of Sheppey, England. Despite implied links to the Roman binders, Parker's ‘Roman cement’ was a true hydraulic cement very different from the hydraulic binders used by the Romans in which pozzolanic materials, not cementitious in themselves, had combined with lime in the presence of water to form insoluble compounds possessing cementing properties. The Roman cement mortars were mainly used in construction where masonry was subjected to moisture and high levels of strength and durability were needed.