Aqua Alexandrina and Fragole cistern: characterization of mortars from Roman constructions, Rome (Italy)

Abstract

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.