Geomaterials and decay forms of the coastal towers of Piscinni and Foghe, Weastern Sardinia

[EN] The distribution of Coastal Towers in Sardinia testify that foreign invasions, which occurred several times over the centuries, were particularly frequent and dangerous. The beginning of the eighth century signed an increase of the attacks from the sea. The most of Coastal Towers were built in the period of Spanish rule, from 1583 to 1720. Despite numerous restorations over the years, many of these defensive structures are in critical conditions, some also affected by structural collapse. The building materials are closely related to local geological outcrops, and consist of sedimentary, magmatic and metamorphic rocks. Study of different lithotypes allowed assessing the vulnerability of different materials in different environmental conditions. Salts, transported by aerosols and deposited inside the porous structures, are the principal cause of decay of the building materials. Chemical-physical and mineralogical-petrographic analyses, performed on some Towers allowed making some general assessments on their conservation status and restoration projects.Carcangiu, G.; Meloni, P.; Palomba, M.; Cocco, O.; Sitzia, F.; Murru, A.; Carboni, M.... (2015). Geomaterials and decay forms of the coastal towers of Piscinni and Foghe, Weastern Sardinia. En Defensive architecture of the mediterranean: XV to XVIII centuries. Vol. I. Editorial Universitat Politècnica de València. 345-352. https://doi.org/10.4995/FORTMED2015.2015.1753OCS34535

Durability of repair mortars used in restoration of a Sardinian coastal tower: assessment after ten years

[EN] This study reports the results of investigations on conservation conditions of an ancient tower, called Torre del Pozzo, located in the S-W coast of Sardinia, restored about ten years ago. The tower suffers from serious problems related to vulnerability of building materials, particularly limestone and sandstones and aerial lime mortar with poor physical-mechanical properties. Over the centuries the materials were subjected to aggressive actions (wind corrasion and salt crystallization) causing an intense erosion of the walls with consequent partial collapse of the structure. About ten years ago a restoration involved the mortars and only the replacement and integration of ashlars deteriorated. After about 10 years from this intervention, some inspections have been carried out in order to assess the effectiveness of the intervention and the state of preservation of the tower. This paper focuses on analyses and tests carried out to assess condition and durability of the repair mortars.Meloni, P.; Carcangiu, G.; Palomba, M.; Enzo, S.; Carboni, M.; Cocco, O.; Casti, M.... (2015). Durability of repair mortars used in restoration of a Sardinian coastal tower: assessment after ten years. En Defensive architecture of the mediterranean: XV to XVIII centuries. Vol. II. Editorial Universitat Politècnica de València. 397-44. https://doi.org/10.4995/FORTMED2015.2015.1761OCS3974

Application of a Novel Method for a Simulation of Conductivity of a Building Material in a Climatic Chamber

This work proposes the application of a new simulation method based on fractal geometry for the calculation of the thermal conductivity for building materials. The results obtained are compared with the measurement, in a climatic chamber, of the heat flow through a material chosen as the sample. The test sample is made with “pietracantone”, a stone widely used as a building material and as an ornamental stone in the areas of Cagliari and Sassari in Sardinia. This material is characterized by a limestone matrix and a porosity which significantly influences the value of thermal conductivity. It is not known to the authors that this material had already been studied for its thermal propertie

Oxamate salts as novel agents for the restoration of marble and limestone substrates : case study of ammonium N-phenyloxamate

The ammonium salt of N-phenyloxamic acid (AmPhOxam) was synthesised, characterised by FT-IR, FT-Raman, UV-Vis, 1H-NMR spectroscopic methods and single crystal X-ray diffraction, and evaluated as a protective and consolidating agent for calcareous stone substrates under mild conditions. Hydro-alcoholic solutions of AmPhOxam were tested for the treatment of naturally weathered white marble and biomicritic limestone. Mercury intrusion porosimetry, FT-NIR spectroscopy measurements and SEM microscopy showed the formation of a superficial protective layer of crystals of the corresponding monohydrated calcium salt, CaPhOxam, on both treated stones.Publisher PDFPeer reviewe

Methodological approach in the conservation of coastal fortifications

[EN] The historical and artistic value of Coastal Towers justifies the recovery of these emblematic artifacts. For the achievement of this objective we propose a methodological approach including: i) architectural relief also by 3D laser scanner and collection of historical data; ii) macroscopic semi-quantitative evaluation of the decay, iii) application of diagnostic quantitative chemical-physical-mechanical methodologies, to assess the decay intensity, and define the criticalities for planning the restoration. The i step allows the graphic rendering of the building showing the geometry and the relationships between the parties. The ii step allows a preliminary understanding of the building materials, macroscopic alteration forms, monument features, acquisition of information about potential causes and decay mechanisms. During the iii step, sampling of building materials is planned. Laboratory analyses, to determine the soluble salts, crystalline phases, porosity as well as micro-textural features of the materials, are carried out by the application of suitable techniques.Carcangiu, G.; Columbu, S.; Meloni, P.; Carboni, M.; Casti, M.; Cocco, O.; Murru, A.... (2015). Methodological approach in the conservation of coastal fortifications. En Defensive architecture of the mediterranean: XV to XVIII centuries. Vol. I. Editorial Universitat Politècnica de València. 341-344. https://doi.org/10.4995/FORTMED2015.2015.1752OCS34134

Consolidating treatment of carbonatic rocks by using diammonium hydrogen phosphate (DAHP): influence of application techniques on the penetration depth

Trabajo presentado en el 5th YOuth in COnservation of CUltural Heritage, celebrado en Madrid (España) del 21 al 23 de septiembre de 2016The diammonium hydrogen phosphate (DAHP) has been recently proposed as an inorganic consolidant to favor the formation of calcium phosphates, mainly hydroxyapatite (HAP), (Sassoni et al., 2011). The objective is to obtain a stone consolidating material suitable to restore the decayed carbonate rocks, making up the building structures of historicalarchitectural interest. A fundamental parameter, for assessing the effectiveness of the consolidating treatments, is the penetration depth of the newly-formed strengthening mineral phases, at present not fully under control. According to Franzoni et al. (2015), the methodologies and techniques of application of the consolidant products, as well as the operating conditions, all can play a fundamental role on the outcomes of treatments. For making a contribution to solve this difficult task, this paper is focused on a systematic experimentation based on the application of aqueous solution DAHP on two different carbonatic lithotypes. Tests were carried out on carbonate lithotypes: Carrara marble (Marmo Statuario Michelangelo) and to a biomicritic limestone, collected in Tuscany and central Sardinia (Santa Caterina di Pittinuri), respectively. These lithotypes are generally greatly affected by alteration phenomena, essentially due to their typical microstructure. Indeed, to different lithotypes correspond different porosity features which can affect, in different way and intensity, the vulnerability and durability of the rocks submitted to the decay weathering agents. The aqueous solution DAHP was applied on the stone, using three different methodological techniques, for different times: immersion, brushing and poultice. The assessment of the results, in terms of penetration depth, were carried out by mappings acquired using the Scanning Electron Microscope (SEM). For both lithologies studied, the greatest penetration depth was achieved with the use of poultice: the presence of calcium phosphates was detected up to 5 mm in marble and up to 10 mm in limestone.Research funded by Geomateriales 2 (S2013/MIT-2914) and by Erasmus+ Placedoc (A.A. 2014/15).Peer reviewe

Mapping of the b value anomalies beneath Mt. Etna, Italy, during July–August 2001 lateral eruption

the spatial variations of the b value in the area studied are real circumstances, linked to the magmatic processes ongoing in that period of time and leading to the eruptive phenomena. Our detailed b value tomography appears to be a good example in which an intrusion activity may be also documented by increased b values. Our analysis demonstrates clearly that the parameter b is a sensitive and accurate indicator of the magmatic processes that occurred during the investigation period at Etna volcano. In summary, the anomalies observed during the two period analyzed (August 1999–June 2001 and July–August 2001) appear to be the result of a fundamental process connected to the magma ascending, ending with a high velocity vertical dike emplacement, which heralded to the July–August 2001 eruption.The pattern of b value of the frequency-magnitude relation, or mean magnitude, has been analyzed as function of space beneath Mt. Etna during the intense lateral eruption of July–August 2001. The data used (August 1999–August 2001), subdivided in the pre-eruptive and eruption period, show significant space variations in the b value. For each of the two periods, a volume of anomalously high b value can be observed in the southeastern flank of the volcano. The anomalies located at 3 ± 1 km (b = 1.84 ± 0.20), and at about 1 ± 1 km (b = 2.11 ± 0.29) depth are interpreted as two different steps of a magma migration process ended with the July–August 2001 eruption. All the available geophysical evidences such as geodetic deformation measurements, focal mechanism and tomographic studies support this interpretationPublishedL053095V. Processi eruttivi e post-eruttiviJCR Journa

Ammonium Methyloxalate as an alternative precursor of Calcium Oxalate for the protection and consolidation of carbonatic decayed materials in cultural heritage

Trabajo presentado en el 3rd International Congress on Science and Technology for the Conservation of Cultural Heritage (TechnoHeritage), celebrado en Cádiz (España), del 21 al 24 de mayo de 2017Peer reviewe

Oxalate and oxamate derivatives: novel synthetic strategies in the design of materials for the restoration of marble and biomicrite limestone substrates

Air pollution, and in particular the presence of sulphur and nitrogen oxides, results in acidic rain determining the dissolution of calcite in marble and limestones. This degradation process induces evident roughness of the stone surfaces and the partial loss of carved details in artefacts. The formation of an artificial coating of calcium oxalate, obtained by treatment with ammonium oxalate, was proved to be a very promising technique for the protection of stone items. The functionalization of oxalic acid to give monoesters and monoamides (oxamates) allows tailoring the solubility of the relevant ammonium and calcium salts. In this context, theoretical calculations carried out at Density Functional Theory (DFT) level can help predicting the capability of the investigated compounds in interacting with the calcium carbonate lattice. We summarize here the experimental (X-ray diffraction, Mercury Intrusion Porosimetry, FT-MIR and FT-Raman spectroscopy, SEM) and theoretical (DFT PES and NBO analysis) investigations on the effects induced by the variation of the functionalized anions in oxalate and oxamate salts on the efficiency of the treatment of marble from the Cimitero Monumentale di Bonaria in Cagliari (Italy) and limestone samples from Cava Flore (Santa Caterina di Pittinuri, Oristano, Italy)