Ancient Roman Mortars from Villa del Capo di Sorrento: A Multi-Analytical Approach to Define Microstructural and Compositional Features

This research provides a characterization of ancient Roman mortars from “Villa del Capo diSorrento” (commonly known as “Villa di Pollio Felice” or “Bagni della Regina Giovanna”). A deepenedanalysis of cementitious binding matrix and aggregates was conducted with the aims of determiningpossible sources of raw materials and the mix recipe, and to evaluate the minerogenetic secondaryprocesses. Twenty samples taken from theVillawere investigated by means of a multi-analyticalapproach, including polarized optical microscopy on thin sections, X-ray powder diffraction, scanningelectron microscopy analysis, energy dispersed spectrometry, simultaneous thermal analyses, andmercury intrusion porosimetry. Bedding mortars were made with slaked lime mixed with volcanicmaterials, whereas coating mortars were made adding to previous recipe as ceramic fragments.All samples were classified as hydraulic mortars. Cementitious binding matrix was characterizedby gel-like C-A-S-H, calcite, hydrocalumite, and gypsum, deriving from lime/pozzolanic material.Geomaterials used for mortar production had a local origin. Pozzolanic materials, such as volcanicfragments, scoriae, pumice, and crystal fragments derived from both pyroclastic rocks of theCampiFlegreidistrict and from rocks of theSomma-Vesuviocomplex; porosity test suggest that the productsrelated to minerogenetic secondary processes, make mortars more resistant.