Stefano Columbu

Hydric dilatation of ignimbritic stones used in the church of Santa Maria di Otti(Oschiri, northern Sardinia, Italy)

In the historical buildings of eastern Logudoro (northern Sardinia), as well as in large areas of western Sardinia, ignimbritic rocks are widely used for ashlars and architectural elements as architraves, pedestals, shafts and capitals of columns. The decay processes affecting these rocks cause a progressive disintegration of the stone ashlars, with loss of material by exfoliation and flaking that determine a progressive retraction of the external profile of the facade with obliteration of the decorative elements. New data on the linear dilatation due to water absorption of these volcanic rocks are presented in this study in order to contribute to the evaluation of the impact of hydric dilatation in the stone degradation. The relationships among linear hydric dilatation of ignimbritic samples and petrographic and mineralogical characteristics as well as physical properties (texture, welding degree, porosity) indicate that three lithotypes with different behaviour in the water absorption can be distinguished in the ignimbrite rocks used as building stones in the church of Santa Maria di Otti (Oschiri, northern Sardinia, Italy). Although the linear hydric dilatation of the ignimbrites is moderate to low, we suggest that hydric dilatation may be an additional factor in enhancing the decay of the stones of the Santa Maria di Otti church.

Cultural Heritage Documentation and Conservation: Three-Dimensional (3D) Laser Scanning and Geographical Information System (GIS) Techniques for Thematic Mapping of Facade Stonework of St. Nicholas Church (Pisa, Italy)

ABSTRACT This article reports the mapping of the stones, including marbles and brick masonry, used for building the facade of the medieval Church of St. Nicholas (XI century ad), one of the most interesting churches in Pisa, due also to the nearby famous octagonal bell tower. Mapping of stone materials was performed using a computer-aided design (CAD)/geographical information system (GIS) software package for storing and processing spatial information of the ashlars, obtained using three-dimensional (3D) laser-scanning data, combined with high-resolution images, and stone-to-stone observations. Based on collected data, the facade of the Church of St. Nicholas appeared mostly composed of rocks belonging to the metamorphic Tuscan sequence, quartzites, and marbles from Mt. Pisano area. Other types of rocks were also observed, as black limestones quarried at some kilometers northwest from Pisa in the Monti d’Oltre Serchio area, white Apuan marbles and Macigno sandstones. Conversely, intarsia appeared mainly made up of serpentinite and, subordinately, red limestones laid in white Apuan and Mt. Pisano marbles.

E.Stone, an archive for the sardinia monumental witnesses

The “E.Stone” project is based on the survey, documentation investigation and physical, geochemical and petrographic characterisation of the great zoomorphic and phytomorphic stones of Sardinia. The name chosen to indicate this project means the full value of these stones, standing before the beginning of human history. The main task of this project is to survey and to document, with an accurate laserscan survey, supported by topographical survey and integrated by GPS tracing and photographic and photogrammetric survey and supported by specific investigations on the rock characteristics. The further development of the collected data will be aimed to the definition of a digital “state of the knowledge” about the stone. This research will produce two main benefits: the creation of a clear and stable archive of these monuments and on the second hand will create the possibility to reply at any distance, a copy in any material of the original item.The focal point of this conference was digital heritage, which all of us involved in the documentation of cultural heritage continually strive to implement. The excellent selection of papers published in the proceedings reflects in the best possible way the benefits of exploiting modern technological advances for the restoration, preservation and e-documentation of any kind of cultural heritage. The topics covered included experiences in the use of innovative recording technologies and methods, and how to take best advantage of the results obtained to build up new instruments and improved methodologies for documenting in multimedia formats, archiving in digital libraries and managing a cultural heritage.

Contribution of petrophysical analysis and 3D digital survey in the archaeometric investigations of the Emperor Hadrian’s Baths (Tivoli, Italy)

This work studies the Heliocaminus Baths. From an architectural point of view, this is a special and unique building in the complex of the Hadrian’s Villa in Tivoli. This research is carried out with a multidisciplinary approach combining petrophysical, petrographic and mineralogical characterization with the techniques of digital survey. The purpose of the research is to contribute to the understanding of Roman construction through the study of materials and from architectural aspects. Using mineral-petrographic and physical analysis, a set of samples (mortars and stones) was investigated for composition and physical properties (density, porosity, water absorption, mechanical strength, etc.). In the case of mortars, these parameters, together with the particle size distribution and the binder/aggregate ratio determined in two ways using image analysis (on thin sections and on specimens), have shown a relationship between the physical and compositional characteristics and the function of mortars within the structure of the Heliocaminus Baths. However, in some cases, different characteristics were detected between the mortars belonging to the same masonry and with same function in the building, showing a slight inhomogeneity in the production of mortars. Furthermore, some relationships between compositional, physical aspects (i.e. porosity, sorting and size of aggregate) and mechanical strength have been found. All the gathered data, linked to the point cloud 3D model, allowed an accurate location of the traces from the construction story of this structure.

Digital Survey and Material Analysis Strategies for Documenting, Monitoring and Study the Romanesque Churches in Sardinia, Italy

The position of the Sardinia Island made it the crossing point of many cultural and political events, but at the same time its isolation has favored the manifestation unique Cultural Heritage phenomena. The network of the Romanesque churches disseminated all around this island clearly shows how an architectural language can be declined. On the bases of different architectural characteristics and petrophysical features of lithologies used, 18 significant churches have been chosen from the different medieval geographical-political areas of the Sardinia named “Giudicati”. Each of these were surveyed with the following methods: photography, 3D Laser Scanner for the whole interior and exterior parts, photogrammetry of a selected set of stone surface samples, direct sampling of representative rocks for geochemical and petrophysical analysis. All data were then treated and analyzed to deepen the knowledge about the most meaningful aspects of different construction techniques and use of materials, provenance of raw geomaterials, stone alterations and structure decay As the result, a base was created to read common behaviors, design choices, recursive constructive solutions, and the “models” guiding the ancient intentions. This contribution will present the progress state of this research and its results.

The ancient pozzolanic mortars and concretes of Heliocaminus baths in Hadrian’s Villa (Tivoli, Italy)

The aim of this work is the physical and mineralogical-petrographic characterization of the mortars from the Baths with Heliocaminus, a special and unique architectural building in the complex of the Hadrian’s Villa in Tivoli. Thirty samples were investigated for composition and physical properties (density, porosity, water absorption, mechanical strength, particle size distribution of aggregate, etc.), representative of eight mortar groups: cubilia bedding mortar, brick bedding mortars, floor-coating and wall-coating bedding mortars, floor (rudus) and wall conglomerates (trullisatio), vault concretes, and lime plasters (arriccio). Physical parameters, together with the microscopic analysis and binder/aggregate ratio determined in three ways using image analysis (on thin sections and on specimens) and weight-data from dissolution of binder, have shown an interesting relationship between the physical-compositional characteristics and the function of mortars within the structure of the Heliocaminus baths. To identify the minerals and the reactant phases between binder and aggregate, as well as the hydraulic degree, selected samples were analyzed with x-ray powder diffraction, thermogravimetry, and differential scanning calorimetry techniques. The obtained results provide a close relation between pozzolanic characteristics and physical-mechanical properties of the mortars (i.e., punching strength index).

Mineralogical, petrographic and chemical analysis of geomaterials used in the mortars of Roman Nora theatre (south Sardinia, Italy)

The composition and the origin of raw materials used in the ancient mortars and concrete of the Nora theatre (first century AD) have been analysed to define their provenance and construction technologies of the Roman period.The use of geomaterials in the binder / aggregate mixtures of the mortars vary according to their function in the different sectors (i.e., structure-wall, tribunalia vaults, wall of external niches, foundation of cavea tiers, stage inner wall) but also according to different construction phases of the theatre or the work-steps. The mortars with structural function are mainly hydraulic (e.g., concrete of vaults, jointing and foundation mortars of cavea ashlars), while the lime mortars were used mainly for plasters, and rarely as bedding mortars. As recommended by Vitruvius, in the hydraulic mortars were mainly used volcanic rocks, as coarse and fine pozzolanic aggregate (pulvis puteolanus), and quartz-feldspar sands (present as crystal-clasts with an almost constant ratio of about 2:1, respectively). The cocciopesto is anomalously rare or absent. In the mortars local dacitic volcanic rock were also used, especially in the concrete as caementia.The grey-black volcanic rocks are glasses with characteristics more near to obsidian and less to natural pozzolan normally used in the Roman period. To identify the provenance of these glasses, a geochemical comparison between the samples taken from the theatre mortars and the volcanic outcrops of some probable Sardinian source areas is made by XRF and SEM-EDS / WDS analysis.To verify the quality of the pozzolan (by its chemical reaction with the binder), the edges and inside of volcanic glasses were analysed with an SEM-EDS microprobe, while the compositional characteristics and the hydraulic degree of the binder was analysed with XRPD and TG/DSC methods, respectively.The use of this kind of pozzolanic glass, without local origins, is a novelty because it has never been found in the mortars of the archaeological site of Nora. Given the wide use of Sardinian obsidian in the Neolithic or Calcolithic periods for production of tools and instruments, some considerations about its use, origin and trade are made.

Geochemical, mineral-petrographic and physical-mechanical characterization of stones and mortars from the Romanesque Saccargia Basilica (Sardinia, Italy) to define their origin and alteration

This paper aims to study the geomaterials of the most important Romanesque-style monument of Sardinia, the Santissima Trinita di Saccargia Basilica (Codrongianos, north Sardinia). The monument was built up on ruins of a pre-existing monastery, and completed in 1116 A.D. Over time, the aspect of the monument is quite changed due to two series of restoration works. The stone materials consist of both grey-black basalts and whitish limestones and marls, intentionally used to give a bichromy effect of the construction. The volcanic rocks belong to the Miocene-Pleistocene volcanic Sardinian activity, while limestones and marls belong to the sedimentary marine Miocene Formation of Meilogu (Logudoro).To define both the origin and the alteration processes of materials, geochemical, petrographic and physical-mechanical investigations of volcanic and sedimentary rocks were carried out on samples collected from monument and possible source outcrops.The integrated chemical (ICP-MS) and petrographic data allowed to ascertain the sourcing sites of raw materials. Moreover, physical-mechanical tests along with X-Ray Diffraction (XRPD) analysis, highlighted the main weathering processes responsible of the chemical-physical alteration affecting the geomaterials, and the newly-formed mineral phases formed on stone surface.

Chronological Classification of Ancient Mortars Employing Spectroscopy and Spectrometry Techniques: Sagunto (Valencia, Spain) Case

Forty-two mortar samples, from two archaeological excavations located in Sagunto (Valencian Community, Spain), were analysed by both portable energy dispersive X-ray fluorescence spectroscopy (pED-XRF) and inductively coupled plasma mass spectrometry (ICP-MS) to determine major and minor elements and traces including rare earth elements (REEs). Collected data were crossed with those previously obtained from Sagunto Castle mortars, and principal component analysis (PCA) was applied to discriminate the construction phases of the unearthed buildings. REE permitted to ascribe most of the masonries to the Roman Imperial period. Moreover, a statistical model was built by employing partial least squares discriminant analysis (PLS-DA) in order to classify the mortars from Roman Imperial period and from Islamic period due to the problematic overlapping between these two phases. Results confirmed the effectiveness of the developed indirect chronology method, based on REE data, to discriminate among historic mortars from different construction periods on a wide scale including different Sagunto archaeological sites.

Geochemical characterisation of pozzolanic obsidian glasses used in the ancient mortars of Nora Roman theatre (Sardinia, Italy): provenance of raw materials and historical–archaeological implications

The study focused on the volcanic glass used in the production of bedding mortars and concrete of the Roman theatre (I cent. AD) of the Nora site. The volcanic glasses were frequently used as aggregate and with pozzolanic function in all hydraulic mortars of the different sectors of the building (e.g., concretes of tribunalia vaults and external niches, jointing and foundation mortars of cavea tier ashlars, brick bedding), together with mainly quartz-feldspar sands, local Oligo-Miocenic andesitic-dacitic volcanics and Palaeozoic and Tyrrhenian sedimentary rocks. These volcanic glasses show characteristics closer to obsidian than to natural pozzolan normally used in the Roman period. They have definitely not sourced locally, unlike the other components that make up the aggregate. To identify their provenance, a petrochemical comparison between several samples taken from the theatre mortars and the volcanic outcrops of some probable Sardinian source areas is made. The use of the not local pozzolanic glass is a technical innovation in the mortars of the Nora archaeological site, and considering the wide use of obsidians in the prehistoric periods for the production of tools, significant considerations about its origin, procurement and use are made.