Microstructure and mineral composition of Roman cements produced at defined calcination conditions

As a part of a major study on 19th century Roman cements a laboratory optimisation study of the calcination of two marls has been conducted within the temperature range 730 to 1100 °C. Strength assessment has shown that the optimum kiln conditions lie towards lower temperatures and differ for the two marls by no more than some 50 °C. aper discusses the clinker properties in terms of phase composition and microstructural features. The textural and mineralogical characteristics of the marl fractions significantly influence the nature and amount of phases formed during solid-state reactions under non-equilibrium conditions. to intermediate calcination temperatures it is mainly the fine-grained matrix of the marls which reacts, while coarse particles remain largely un-reacted. The major reactive crystalline phases identified in the optimum cements are belite in two polymorphs and free lime, while a number of other compounds remain unclear because of their non-crystalline nature.