Understanding the 16th century coastal watchtowers: Material characterisation of Torre Gregoriana (Italy)

The building materials employed in Torre Gregoriana (1582-85), Terracina, have been investigated. The study focuses on the physical, chemical and mechanical characterisation of mortars, bricks and stones. The aim is to provide further insights on the knowledge of the military engineers of the time as well as to outline the material characteristics for the sake of defining compatible repair materials, details which are still missing to date. The results highlight that, due to the emergency of Turkish invasions in this period, great care was used in the building of these constructions, resulting in an accurate selection and distribution of materials by the builders (mainly hydraulic mortars and pure limestone units) and the intentional addition of reactive aggregates (such as glass particles and iron slag) for improving the durability of the structure against the aggressive marine environment.