Integrated approach for post-fire reinforced concrete structures assessment

In order to assess decay in the mechanical characteristics of re-exposed Reinforced Concrete (RC), it is crucial to recon- struct the temperature time history and the evolution of strain and stress elds. In this paper, the state of the art of assessment methods is presented and applied to a real structure damaged by re. It is a prestressed RC industrial warehouse located in the outskirts of the city of Cagliari (Italy). The collected data of several assessment methods are presented in order to produce the owchart of an integrated approach for post- re investi- gation. Among the various techniques, the authors highlight a thorough laser scanner geometric survey and destructive and non-destructive testing. In addition, the temperature distribu- tion and its time history has been reconstructed by means of optical and Scanning Electron Microscopy, X-ray diffractom- etry, Thermogravimetric Differential Thermo-Analysis and calibrated Colorimetry. Actually, refurbishment is needed, but the structure withstood the re very well. Central columns displayed the most impor- tant damage, and several beams presented important de ec- tions having lost the prestressing actions of the tendons

Workability and chemical-physical degradation of limestone frequently used in historical Mediterranean architecture

Sedimentary rocks are among the most used in historical buildings, as they are more readily available in the area and because they are also more easily extractable, in virtue in general of lower mechanical resistance. among these the most used are limestones and sandstones. The former are represented by a remarkable variety of lithologies, with highly variable characteristics, passing from the almost pure, massive and not very porous limestones, to those with a variable arenaceous-clayey component which instead are characterized by a low compactness and consequent high porosity (up to 35%). In this study the calcarenites present in two geographic sectors of Sardinia are dealt with, by comparing them with similar showers present in other territorial contexts of the Mediterranean. The mineralogical-petrographic analyzes by optical microscope and XRD analysis of the "Pietra Cantone" limestone of Cagliari (south Sardinia) show, besides calcite, the presence of phyllosilicates and various other accessory minerals. SEM analyses show a very weak physical-mechanical microstructure

Pyroclastic Stones as Building Materials in Medieval Romanesque Architecture of Sardinia (Italy): Chemical-Physical Features of Rocks and Associated Alterations

The paper discusses the chemical-physical-petrographic features and decay processes of San Nicola Church (11th−14th century) building materials, one of the most representative Medieval Churches in Sardinia, stylistically attributable to the Romanesque architecture. The monument was built up into two stages and shows a characteristic size uniformity of the ashlars. The masonry is mainly made up of rhyodacitic pyroclastites belonging to the Sardinian Eocene-Miocene mag- matic phase (38–15 My). These volcanic rocks were widely used in Medieval architecture for the excellent workability, but its minero-petrographic features greatly favor the decay, due to the action of chemical-physical alteration processes. Although the alteration degree and macroscopic forms of decay vary from zone to zone in the monument, according to the different compositional features of the volcanic stones, weathering and exposure condition, the pyroclastic rocks are generally affected by greater alteration than other igneous lithotypes, due to their petrographic- volcanological characteristics (e.g., low-medium welding grade, medium-high porosity). The results concerning mineralogical and petrographic features, respectively, carried out by the application of X-Ray Powder Diffraction (XRPD), Optical Microscope (OM), and Scanning Electron Microscope (SEM) techniques, both on fresh building rocks and associated alterations, are here presented and discussed. Furthermore, the relationships between fresh pyroclastites and altera- tion processes affecting these rocks will be discussed

The ancient mortars and geomaterials of tower fortification of Nora (Pula, Sardinia, Italy)

[EN] The tower is located on a promontory on the south-western Gulf of Cagliari, near to the Coltellazzo island and the archaeological Punic-Roman of Nora. The first military settlement was probably present since the beginning of the fourteenth century. Surely the tower was active since 1607. Jorge Aleo (1680) mentions, calling Fortalleza Coltellaz. In the eighteenth century the building was engulfed in a fort, built in a period of six years (1722-1728) by engineer the Piedmont Antonio Felix de Vincenti. Later (in the nineteenth century) further work was carried out until the tower became a lighthouse. The tower was considered a tower de armas or vigorous, or for heavy defense, with a garrison of men under a commander. Being a watch tower, is in sight of the towers of Cala d'Ostia, San Macario and the Diavolo. The tower has a structure of a truncated cone, with a height of about 11 meters high and 12 meters in diameter at the base. Inside it has a double ribbed vaulted dome, supported by a central pillar. The aim of this research is were studying mortars and geomaterials used of the ashlars, for define: i) composition of ancient mortars with ratio binder/aggregate; ii) provenance of the raw materials used in the mixture of mortars; iii) alteration processes in progress on mortars and on geomaterials used in masonry. Through the analysis of the physical-mechanical properties, important evidences of chemical and physical decay were highlighted in the mortar of the plasters coating the tower and also in bedding mortars of ashlars of masonry. In some areas, where they are concentrated processes of physical disintegration, also as a result of dissolution of the carbonate matrix of the mortar, show scarce resistance physical-mechanical with consequent detachment from the masonry.Columbu, S.; Carcangiu, G.; Sitzia, F. (2015). The ancient mortars and geomaterials of tower fortification of Nora (Pula, Sardinia, Italy). En Defensive architecture of the mediterranean: XV to XVIII centuries. Vol. I. Editorial Universitat Politècnica de València. 357-364. https://doi.org/10.4995/FORTMED2015.2015.1755OCS35736

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

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

Integrated Approach for Post-fire Reinforced Concrete Structures Assessment

In order to assess decay in the mechanical characteristics offire-exposed Reinforced Concrete (RC), it is crucial to reconstructthe temperature time history and the evolution of strainand stress fields. In this paper, the state of the art of assessmentmethods is presented and applied to a real structure damagedby fire. It is a prestressed RC industrial warehouse located inthe outskirts of the city of Cagliari (Italy). The collected data ofseveral assessment methods are presented in order to producethe flowchart of an integrated approach for post-fire investigation.Among the various techniques, the authors highlight athorough laser scanner geometric survey and destructive andnon-destructive testing. In addition, the temperature distributionand its time history has been reconstructed by means ofoptical and Scanning Electron Microscopy, X-ray diffractometry,Thermogravimetric Differential Thermo-Analysis andcalibrated Colorimetry.Actually, refurbishment is needed, but the structure withstoodthe fire very well. Central columns displayed the most importantdamage, and several beams presented important deflectionshaving lost the prestressing actions of the tendons