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Earthquakes often occur along faults in the presence of hot, pressurized water. Here we exploit a new experimental device to study friction in gabbro faults with water in vapor, liquid and supercritical states (water temperature and pressure up to 400 °C and 30 MPa, respectively). The experimental faults are sheared over slip velocities from 1 μm/s to 100 mm/s and slip distances up to 3 m (seismic deformation conditions). Here, we show with water in the vapor state, fault friction decreases with increasing slip distance and velocity. However, when water is in the liquid or supercritical state, friction decreases with slip distance, regardless of slip velocity. We propose that the formation of weak minerals, the chemical bonding properties of water and (elasto)hydrodynamic lubrication may explain the weakening behavior of the experimental faults. In nature, the transition of water from liquid or supercritical to vapor state can cause an abrupt increase in fault friction that can stop or delay the nucleation phase of an earthquake. Earthquakes often originate along faults in the presence of hot and pressurized water. Experiments conducted on simulated faults reveal that the physical state of water (liquid, vapor or supercritical) controls the frictional resistance of faults. [ABSTRACT FROM AUTHOR]

This paper is focused on the application of Infrared Thermography to non-standard rock specimens, in terms of size and deterioration conditions, of Hungarian tuff to monitor their cooling process and to look for a relationship between the rock Cooling Rate Index and the porosity. Literature data agree on the potential of Infrared Thermography for the indirect estimation of rock porosity in fresh specimens through the IRTest, but this technique has never been tested on non-standard specimens. To this purpose, tests on three varieties of Hungarian tuffs were carried out. These materials were selected for their cultural importance linked to their usage as building stones and in other historical applications in Northern Hungary. Tuff specimens underwent a fixed number of salt crystallization cycles. The Cooling Rate Index (CRI) for each specimen was calculated according to the literature experience and correlated to their porosity estimated by water, helium, and mercury intrusion. The results show that the rock cooling process is related to porosity since more porous rocks are characterized by faster cooling. Positive linear trends were achieved for weathered specimens considering 20 min monitoring (CRI20), which is double the time suitable for untreated rocks. The reason should be searched in salt crystallization's effects on the rock texture, paving the way to further studies on this pioneering branch of technological application. [ABSTRACT FROM AUTHOR]

This study presents the petrographic and chemical characterization of the frescoes in the Church of San Panfilo in Tornimparte (AQ, Italy) by Saturnino Gatti, a prominent painter of the late 15th–early 16th century, known for his exquisite technique, composition, and use of color. The characterization of the frescoes is essential for understanding the materials and techniques used by Gatti, as well as for identifying the stratigraphy and painting phases. Eighteen samples were collected from the original paint layers, later additions (17th century), and restored surfaces, and analyzed by optical microscopy, cathodoluminescence microscopy, scanning electron microscopy (SEM-EDS), μ-Raman, and electron paramagnetic resonance (EPR). The analyses revealed a microstratigraphy often made of three main layers: (1) preparation, consisting of lime plaster and sand; (2) pigmented lime, applied by the fresco technique; and (3) additional pigmented layer on the surface. The most often recurring pigments are black, red, yellow (all generally linked with the fresco technique), and blue (applied "a secco"). The presence of two painting phases was also noted in one sample, probably resulting from a rethinking or restoration. These findings contribute to the understanding of the history and past restoration works of this cultural heritage site, providing important insights not only for conservators and restorers, but also for a broader understanding of Italian fresco painting and art history of the late 15th and early 16th centuries. [ABSTRACT FROM AUTHOR]

Tidal exchange, capillary rise, water condensation-evaporation cycles, and crystallization of salts are the main causes of damage in historic brick buildings in Venice. The present study addressed these issues by proposing a study of twenty-three brick samples collected on the main façade of the Santa Maria dei Servi Church (14th century). The color, mineralogical composition, and texture of these samples were studied using standard methods such as spectrophotometry, X-ray powder diffraction (XRPD), optical microscopy (OM), and field emission scanning electron microscopy (FESEM). The presence of carbonates (calcite and dolomite) and newly formed silicate phases, such as gehlenite and diopside, provided indications of the temperatures reached during firing and suggested the absence of a good standardization in the production process. Meanwhile, XRPD and hyperspectral analysis (HA) detected sulfates (e.g., gypsum and mirabilite) as the main weathering products due to the salt decay process that affects monuments in the Venice lagoon environment. Moreover, secondary phases, such as Mg- and Ca-zeolites, occurred in bricks where the groundmass observed by OM was more vitrificated, and the XRPD patterns displayed the highest amorphous content. On-site mapping of sulfates and chlorophyll by HA was also performed on the main façade of the Church, highlighting the large presence of salts and biodeterioration. [ABSTRACT FROM AUTHOR]

This work presents a methodology for obtaining a quantitative expression of the superficial deterioration of bricks affected by climatic conditions. The method combines in situ measurements with laboratory data. Input data on material recession were obtained from photogrammetric observations, the material properties were derived from laboratory tests or the relevant literature, and climate data were provided from regional environmental monitoring service. The climatic parameters considered in this study are: relative humidity, number of freeze-thaw cycles (i.e., mean number of days per year with temperatures below zero), and peak sun hours per day. The methodology proposed estimates the deterioration rate of brick façades under variable climate conditions over time. As a conclusion of this research, a new tool for the structural evaluation of brick walls is presented. [ABSTRACT FROM AUTHOR]

An innovative experimental method for the long-term monitoring of outdoor microclimate and material decay at cultural heritage sites was developed to aid the formulation of new damage functions and models for climate-change risk assessment. To that end, an apparatus for field exposure tests was designed to monitor a variety of historical building materials in different environmental settings. The data series acquired, i.e., surface temperature and moisture, are compared with the corresponding meteorological datasets on a local and regional scale. The apparatus is designed for supporting also the monitoring of the physical and chemical changes caused by weathering. This novel method is expected to provide insights into the interaction between historical materials and the environment, which can be exploited for the protection and conservation of cultural heritage. [ABSTRACT FROM AUTHOR]

Abstract: Roman colonization of northern Italy during the late Republican Age brought about significant building activity in the newly acquired territories, involving the construction of new infrastructure that demanded large amounts of stone. Trachyte of the Euganean Hills was among the most commonly used materials for building roads, bridges, forum squares, and aqueducts. This paper addresses the recognition of the provenance quarry of Euganean trachyte used in Roman public infrastructure in northeastern Italy. Petrographic features and major‐ and trace‐element composition of bulk rock and phenocrysts, analyzed by X‐ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS), were used as provenance tracers. The provenance determinations allow for exploring the commercial, political, and economic dynamics involving the supply of trachyte for public works, and the management of Roman quarries, which likely were in competition with each other and separately controlled by the most important nearby cities. Finally, broad insights into ancient trades in northern Italy and the main routes of stone distribution are discussed: most transport was done by ship, being more rapid and less costly, taking advantage of the Adriatic Sea, the Po River, and the many waterways close to the Euganean quarries. [ABSTRACT FROM AUTHOR]

Abstract: Trachyte of the Euganean Hills is a subvolcanic porphyritic rock historically used as carving and building stone in northern and central Italy–primarily from Roman times onward–with the first evidence of its use dating back to prehistory. The numerous quarries and very similar trachyte varieties, as well as the widespread use of this stone, create several problems in defining its provenance for archaeological and historical materials. New petrographic and geochemical tracers for recognizing the provenance quarry of Euganean trachyte are presented here, providing a comprehensive reference database for archaeometric studies. The petrographic markers principally include quantitative data on mineralogical composition and textural features of phenocrysts and groundmass, determined by image analysis of chemical maps acquired by micro X‐ray fluorescence and scanning electron microscope‐energy‐dispersive X‐ray spectroscopy; particular use has been made of data on the abundance and grain‐size distribution of feldspar phenocrysts, phenocrysts‐groundmass ratio, content of SiO2 phases in the groundmass, and the arrangement and grain‐size of microlites in the matrix. The geochemical tracers involve composition of bulk rock and phenocrysts, determined by X‐ray fluorescence and laser ablation inductively coupled plasma mass spectrometry, respectively; quarry recognition can be achieved using plots built from concentrations of major and trace elements, with mineral‐scale chemistry being the most effective and precise discriminant property, especially in the case of biotite and, secondarily, augite, kaersutite, and magnetite. [ABSTRACT FROM AUTHOR]

Decay of trachyte used as building stone in urban environment was investigated through the analysis of crusts and patinas found on trachyte of the Euganean Hills in the Renaissance city walls of Padua, northeastern Italy. Mineralogical and microstructural characteristics of the alteration products, as well as major- and trace-element chemical composition, were determined by optical microscopy, SEM-EDS and X-ray mapping, XRPD, and LA-ICPMS. The results are discussed referring to environmental parameters, in particular concerning air quality and anthropic pollution sources. The influence of composition of the stone and other neighboring materials on specific weathering processes is also debated. The formation of crusts and patinas turns out to be mainly due to exogenous processes. Enrichment in heavy metals and carbonaceous matter derives from the deposition of particulate emitted during fuel combustion by road vehicles, domestic heating and, secondarily, industrial activities. The particulate is typically cemented by calcite, mainly mobilized after dissolution from nearby mortar joints, or iron, released by leaching from iron-bearing minerals, reprecipitated according to pH fluctuations. Gypsum layers were rarely observed. Generally, composition of the weathering crusts and patinas of Euganean trachyte proves to be an informative marker for the relevant environmental conditions and their evolution. [ABSTRACT FROM AUTHOR]

Volcanic tuffs have a historical tradition of usage in Northern Hungary as dimension stones for monumental construction, Ottoman architecture, common dwellings, etc., admirable at its best in the medieval castles of Eger and Sirok. This research explores tuff deterioration in the castle walls, dealing with the mineralogical composition, microstructure, trace-element geochemistry, and microporosity of the surface weathering products and the near-surface stone substrate. The classic microscopic and mineralogical techniques–optical microscopy, SEM-EDS, and XRD–were supported by ICP-MS and nitrogen adsorption analyses. The textures and mineral assemblages of the tuffs are partly diverse, and so are the weathering characteristics, although including common features such as secondary crystallization of gypsum, swelling clay minerals, and iron oxides-hydroxides; deposition of airborne pollutants, i.e., carbon particles and heavy metals; formation of crusts and patinas; decreased surface microporosity. Nonetheless, the entity of deterioration varies, in relation to air pollution–involving changing emissions from road and rail transport–and the specific tuff texture, porosity, and durability–affecting pollutant absorption. The studied stone monuments offer the possibility to examine materials with analogue composition and petrogenesis but utilized in different environmental contexts, which allow pointing out the environmental and lithological constraints and cause-effect relationships related to surface weathering. [ABSTRACT FROM AUTHOR]

Volcanic tuffs are notoriously very heterogeneous materials exhibiting a recurrent lithological diversity, which, in turn, can be associated with changing petrophysical and mechanical properties. This variability was investigated on a small scale in different Miocene acid tuffs from Hungary, extracted in the same quarry region, within a few km radius from the town of Eger. They have been exploited since the Middle Ages and used for common construction and historical monuments – castles, churches, Ottoman architectures – or excavated and carved for creating wine cellars, cave houses, ritual sites, etc. These pyroclastic rocks are compositionally analogue but turn out to show unexpected major differences in texture and technical properties, which affect their resistance to decay. The rate and intensity of weathering, examined in laboratory conditions by freeze-thaw and salt attack tests, is governed mainly by the following properties: open porosity; relative abundance of pumice, crystals, and groundmass; pore-size distribution; and tensile strength. Nevertheless, open porosity – which here is proportional to water absorption and indirectly related to mechanical performance – is considerably different among the tuff varieties, and this seems to be the most significant factor marking the diverse durability. That is questionable in case of unpredicted textural diversities, e.g., enrichment in pumice and higher concentration of groundmass. Therefore, without rejecting the importance of complementary tests, a basic and fast study involving thin-section examination and open-porosity measurement would be sufficient for providing many indications on the quality of these materials and for the selection of dimension stones for restoration of historical heritage and construction. [ABSTRACT FROM AUTHOR]