Early exploitation of Neapolitan pozzolan (pulvis puteolana) in the Roman theatre of Aquileia, Northern Italy

Abstract

The paper reports the results of the analyses on mortar-based materials from the Roman theatre of Aquileia (Friuli Venezia Giulia, Northern Italy), recently dated between the mid-1st Century BCE and the mid-1st Century CE. Samples were characterized by Polarized Light Microscopy on thin sections (PLM), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM–EDS) and Quantitative Phase Analysis by X-Ray Powder Diffraction (QPA-XRPD). Pyroclastic aggregates (mainly pumices and scattered tuffs), incompatible with the regional geology, were found in two samples from the preparation layers of the ground floor of the building. Their provenance was determined by means of QPA-XRPD, SEM–EDS, X-Ray Fluorescence (XRF) and Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS). Mineralogical and geochemical analyses demonstrated their provenance from the Bay of Naples, thus recognizing them as pulvis puteolana, a type of pozzolanic aggregate outcropping around the modern town of Pozzuoli and prescribed by Vitruvius (De Architectura, 2.6.1) in mortar-based materials to strengthen masonries and produce hydraulic concrete for harbor piers. This evidence represents the oldest analytically-established case of pulvis puteolana exploitation in Northern Italy up to now, and an early use of the material out of Campania adapted for civil constructions in a non-strictly maritime-related environment. Indeed, the theatre was built in the low-lying Aquileia’s deltaic plain, prone to water infiltrations that are typical in lagoon-like environments. The data highlight the craftsmen’s resilience in adapting and reinterpreting the traditional use of the Neapolitan volcanic materials to deal with the geomorphological challenges of Aquileia’s lowland.

MgO‐based binders

“…Long-term and durability studies of M-S-H cements are not reported in literature. However, M-S-H cements show a high resistance against carbonation [12,13] as also underlined by the observation of M-S-H in some Roman cements [41].…”

“…Magnesium from the seawater or clay water reacts with the amorphous silica from the degradation of C-S-H in cement leading to the formation of M-S-H [40]. M-S-H has also been observed in Roman cements rich in chert and dolostone [41] indicating a long-term stability of M-S-H. Electron microprobe, SEM/EDS and TEM analyses indicate that M-S-H contains not only magnesium, silica, hydroxides and water but that aluminium, calcium and iron can be incorporated in its structure [42,43].…”

MgO-based cements – Current status and opportunities

“…MS cements could also be used as cements for building materials containing natural fibers or bio-aggregates [174,175] as they present lower pH values and seem to be more compatible with such organic-based aggregates than PC systems [175][176][177]. Finally, the M-S-H phases are very stable [178] and present a strong potential as durable cements for low-CO 2 construction.…”

A Multianalytical Approach to Identifying the White Marbles Used in Roman Imperial Sculptures from Tarraco (Hispania)

“…This contribution, therefore, is framed within the studies of the provenance of stone materials, where archaeometry is of enormous interest in marble studies. In recent years, archaeometry has also been efficiently applied in the definition of the sources of other types of stones used to make artifacts [26], infrastructure [27] or even to know the origin of the additives found in Roman concrete [28].…”