Aqua Alexandrina is the last aqueduct built by ancient Romans for the city of Rome. At Giovanni Palatucci Park, the archaeological ruins run close to a pre-existent water system, Fragole cistern. This research aims at characterizing mortar samples from both constructions, to identify the materials used and infer about the technological level and the provenance of materials, using a multi-analytical approach. Combining the information obtained through the petrographic investigation of mortar thin sections at optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray powder diffraction on finely powdered samples and thermogravimetric analysis on the binder fraction, it was possible to attest the presence of both artificial and natural materials with pozzolanic behavior, which conferred hydraulicity to the mortars. The results show that materials are very similar in both constructions, confirming a well-established know-how in the production of hydraulic mortars by the Romans. The volcanic products used as aggregate are identified with two large pyroclastic-flow deposits erupted by the Colli Albani Volcanic District which extensively crop out in the area of Rome: Pozzolane Rosse and Pozzolanelle.

Construction materials from the internal ducts of Aqua Traiana, a still operative Roman aqueduct built in 109 AD to supply water to Rome, were characterized by optical microscopy (OM), scanning electron microscopy (SEM-EDS), X-ray powder diffraction (XRPD) and electron microprobe analysis (EMPA). Petrographic analysis and XRPD revealed that mortar aggregates are compatible with Vitruvius’ harena fossicia and allowed the distinction of the original mortars from those of the 17th-century papal restoration. The first showed an amorphous binder while the latter have a typical lime binder. By SEM-EDS and EMPA, the microstructure of mortar aggregates was analyzed and the composition of specific minerals quantified. Microanalysis testifies the Romans’ great expertise in the selection of pozzolanic building materials, giving evidence of the possible use of local tuffs from the Sabatini Volcanic District. It also confirms the exploitation of red pozzolan from the Roman Magmatic Province, specifically from the Alban Hills district. OM also proves a high compatibility with local supplies for bricks and cocciopesto. Of these, the first were fired at moderately low temperature, while the latter show an amorphous binder as in the original Trajan mortars. All building materials thus stand for similar technological choices and a coeval production.

Despite the archaeological importance of Aqua Virgo, a Roman aqueduct built in 19 BC and still functioning nowadays, there is a lack of information about the mortars coming from the inner duct. This work aims to investigate the mortars from Aqua Virgo and Aqueduct Y, an unidentified aqueduct running under the first one in the La Rinascente area (between Via del Nazareno and Via dei Due Macelli, Rome, IT) through Optical Microscopy (OM), X-ray Powder Diffraction (XRPD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The aim is to understand which materials guarantee such longevity and differentiate between different intervention phases. Local natural materials with pozzolanic behaviour—in particular, Pozzolane Rosse—and ceramic fragments are widely employed, mixed or not, for the realisation of the hydraulic mortars under investigation, independently of the intervention phase. Of particular interest is the discovery of an amorphous binder composed of Si, Al, Ca, K and Mg in some samples characterised by the absence of calcite.