Characterization of the ancient mortars and 3D laser scanner survey to define the construction phases of the Heliocaminus Baths in the Hadrian's Villa (Tivoli, Italy)

Inside the Hadrian’s Villa in Tivoli, it is possible to see the ruins of special and unique buildings, aimed at their time to create spectacular places, to give appropriate spaces to the court and to the people living in this architecture masterpiece. The reading of these structures sometimes is not easy, so the main idea in this project is to start from the small evidences in the single buildings, find rules and solutions to combine them into a global digital survey based on a 3D digital model and then start using this model for hypothesis formulation. This kind of approach should only be multidisciplinary combining the knowledge about petrographic, mineralogical and chemical characterization with the techniques of the digital survey (using 3D Laser Scanner based solutions) and the reading of the architectural aspects. The research presented here will propose this methodological approach as the tool to interpreter the different construction phases of the Heliocaminus baths (II Century A.D.): the first personal spa of Emperor Hadrian. Using mineralogic-petrographic (by optical microscopy and XRD) and physical analysis a set of samples were investigated for their compositional aspects of the aggregate and of the pozzolanic binder of mortars, and their physical characteristics (real and apparent densities, open and closed porosity, water absorption kinetic, mechanical strength, etc.). These parameters, together with the analysis of the aggregate particle size and morphology, and a proper analysis of the relationships binder/aggregate, have shown a clear relationship between the physical-compositional characteristics of mortars and their function within the structure of the baths. Then, through the differential thermal analysis (TGA, DSC) it has been studied the hydraulic degree of mortars, which is also linked to the kind of aggregate and pozzolanic materials used. All this has allowed us to detect some compositional discrepancies between the different mortars used in this building, even within the same room, highlighting how the Heliocaminus baths was carried out in several stages, with interruption of the construction works and with an evident change in the workers operating in its courtyard. All the gathered data, linked to the pointcloud 3D model of the Heliocaminus baths allowed an accurate location of all the meaningful traces of the story of this structure giving confirmations to the high architectural value of specific and innovative solution of that age. The contribution of the scientific analysis of the samples puts in evidence the importance of correct and innovative solutions in cultural heritage approach with proper technologies.