The Hydration of Modern Roman Cements Used for Current Architectural Conservation

Roman cement was extensively used to decorate façades during the nineteenth and at the beginning of the twentieth century. Interest in this material has revived recently for the conservation of architectural Cultural Heritage, using new production sources. This article gives preliminary results on the characterisation of the raw materials and the main reactive phases (using XRD, SEM, selective dissolution and isothermal calorimetry) of a Roman cement recently produced from the Lilienfeld marlstone (Austria), compared with a commercial Roman cement (Vicat, France). The mineralogical composition of the two cements differs strongly due to the presence of sulphate minerals in the marlstone and on the temperature of calcination. Isothermal calorimetry and in-situ XRD carried out on cement pastes allow the identification of the AFm and AFt type phases as early age hydration products responsible for the flash setting typical to Roman cements. The alumina rich composition and the polymorphs of dicalcium silicates is strongly different in the Lilienfeld cement. This influences their reactivity at the later ages.