The mechanical resistance of saturated stones

This paper aims at investigating the effect of the presence of water on the mechanical resistance of stones. The presence of water, connected to the intrinsic properties of the stone (mineralogical composition, fabric, texture, etc.) and to the conditions of use (anchoring systems, climatic parameters, etc ), is the main cause of stone decay. However, the presence of water alone inside stone could cause a decrease in mechanical resistance . The obtained data could in fact be useful to correct the safety coefficient and should be taken into account in the planning of structural stonework. Moreover, useful suggestions can be drawn for the in situ monitoring, taking into account that non destructive tests, together with conventional mechanical methods, are influenced by the presence of water in stones and should be corrected. Three kinds of stones, which have historically been used for structural purposes, have been studied: Pietra di Luserna (gneiss, Piedmont, Italy), Pietra Verde Argento (gneiss, Piedmont, Italy) and Pietra di Courtil (mica-schist, Aosta Valley, Italy). The flexural strength, rupture energy, open porosity and ultrasonic pulse velocity (UPV) have been determined on specimens in dried and saturated conditions at different accelerated ageing steps. As far as the UPV test is concerned, its results are well correlated with the flexural strength values but, without other parameters, it cannot give information on whether the specimen is filled with water, therefore suitable procedures to correct the UPV value obtained in situ are suggested. Destructive methods, and in particular the flexural strength method, instead, give lower resistance values for saturated specimens than dried ones, thus confirming the weakness of the stone due to the water insid

Vicoforte sandstone in Cultural Heritage

The large family of sandstone covers stones with different grains, porosity, cement or matrix, compactness, chemical composition etc. and it is widely used as cladding stone, even in historic buildings. From literature, its decay is usually connected to the action of salts or to black crusts because of pollution. Being sandstone a sedimentary rock deposited in layers, often the quarry produce material with a high variability in aspects and mechanical properties. This can be also evident in the resistance to decay shown in the monuments that is typical of each facies though it has been exposed for the same lapse of time and under similar climatic conditions. This is the case of Arenaria di Vicoforte used on the facade of the Vicoforte Sanctuary (Vicoforte - Mondovì) and probably on the external pilaster of the Monte dei Cappuccini church in Turin. Both the catholic monuments were designed by architect Ascanio Vitozzi at the end of the XVI century . It is possible to compare the high degree of weathering of the pilasters of the Monte dei Cappuccini church with the good ageing behaviour shown by the Vicoforte Sanctuary sandstone. Different durability tests were carried out: resistance to salt crystallisation, resistance to ageing due to SO2 action in the presence of humidity, frost resistance. The mass weight difference, method used to evaluate the forecast of decay in various european standardardized methodologies, does not always offer a satisfactory estimation of the decay of stone after salt crystallization while water absorption, which is well correlated to the physical mechanical characteristics of the stone, together with a visual inspection, is a good index of the decay in order to obtain a distinction, in terms of durability, between different sandstones even of a same geological district. A visit to the quarry solved any doubts: two different facies of the Vicoforte sandstone were quarried, one yellowish and the other grey. The first, mainly silicatic, was used for the Sanctuary near the quarry, the grey one (with a carbonate content of 18%) could be the one sent to Turin. The variability of the rock characteristics in the quarry should therefore be taken into account when evaluating the durability of the sandstone

Italian travertine in building heritage

Travertine is one of the most common stone for building construction used in many countries starting from ancient times. It was one of the favorite stones of the Roman empire: the main example is the Colosseum in Rome. All over the world travertine is found in important monuments and in various modern structures: for example, the Conservation Center of the J. Paul Getty museum in Los Angeles and Jiangsu Provincial Art Museum in Nanjing, China and it is very appreciated and requested in the construction of recent thermal bath. In addition to Italian travertine, the other famous types of this stone are known throughout Europe (i.e. Germany, Hungary) and Asia (i.e. Turkey, China, Iran). Travertine is considered a durable stone despite the weathering caused by air pollution. It is observed in urban areas that the facades may be covered with a black crust where gypsum and calcite are the main minerals . Nine different types of travertine coming from Tuscany and Umbria (Italy) have been investigated. Petrographic analysis, physical mechanical and artificial ageing test have been performed. Among the different kind of travertine different texture can be identified as: not laminated, laminated: laminated with sub parallel sheets, laminated with concentric sheets. The various travertine depositional structures have been in compared to the different answer to artificial ageing. Finally, it can be asserted that the durability is not connected only with porosity and the analysis of the complex texture of this kind of stone cannot give a simple solution related to its durability

La pietra naturale nei beni culturali

Le pietre ornamentali ricoprono un ruolo fondamentale per quei beni culturali costituiti parzialmente o interamente in materiale lapideo. In un contesto come quello italiano, la conoscenza dei litotipi utilizzati in ciascun ambito regionale, sia per le produzioni artistiche di pregio che per l’edilizia corrente, riveste certamente una particolare importanza. Infatti, l’impiego della pietra ha da sempre connotato in maniera determinante il paesaggio urbano e rurale. Lo studio dei litotipi ornamentali, la loro caratterizzazione e la loro conservazione rivolge l’attenzione sui materiali posti in opera e rappresenta una branca delle Scienze Geologiche e delle Scienze applicate ai Beni Culturali. Tale ricerca, regolata e normata secondo standard nazionali e internazionali, permette di ampliare l’esperienza scientifica e culturale. I materiali lapidei, la cui scelta d’impiego fu ed è tutt’oggi tutt’altro che casuale, rappresentano parte della storia e ne rappresentano il patrimonio tangibil

The mechanical resistance of saturated stones

This paper aims at investigating the effect of the presence of water on the mechanical resistance of stones. The presence of water, connected to the intrinsic properties of the stone (mineralogical composition, fabric, texture, etc.) and to the conditions of use (anchoring systems, climatic parameters, etc ), is the main cause of stone decay. However, the presence of water alone inside stone could cause a decrease in mechanical resistance . The obtained data could in fact be useful to correct the safety coefficient and should be taken into account in the planning of structural stonework. Moreover, useful suggestions can be drawn for the in situ monitoring, taking into account that non destructive tests, together with conventional mechanical methods, are influenced by the presence of water in stones and should be corrected. Three kinds of stones, which have historically been used for structural purposes, have been studied: Pietra di Luserna (gneiss, Piedmont, Italy), Pietra Verde Argento (gneiss, Piedmont, Italy) and Pietra di Courtil (mica-schist, Aosta Valley, Italy). The flexural strength, rupture energy, open porosity and ultrasonic pulse velocity (UPV) have been determined on specimens in dried and saturated conditions at different accelerated ageing steps. As far as the UPV test is concerned, its results are well correlated with the flexural strength values but, without other parameters, it cannot give information on whether the specimen is filled with water, therefore suitable procedures to correct the UPV value obtained in situ are suggested. Destructive methods, and in particular the flexural strength method, instead, give lower resistance values for saturated specimens than dried ones, thus confirming the weakness of the stone due to the water inside

Characterization of sludge resulting from the extraction and processing of natural stones. focus on a Piedmont case

The problem of the management of sludge resulting from the extraction and processing of ornamental stones is currently one of the key issues for the European Union and for Italy. The European Community, through Directive 2006/21/EC (Management of waste from extractive industries – Mining waste), Directive 2008/98/EC (Waste Framework) and Directive 1999/31/EC (Landfill Waste), has provided guidelines for its member countries on how to handle wastes, in view of a future sustainable development of the sector, especially as far as critical raw material (CRM) is concerned. In this context, an analysis of the procedure applied to extract and cut two similar Piedmont silicatic stones into slabs and to manage their sludge has been carried out. The ornamental stones taken into consideration are Diorite of Traversella and Perosa Stone (Dioritic gneiss). The following procedures were conducted to characterise the stones: petrographic analysis, as well as compressive strength, flexural strength, impact resistance and water absorption tests. This characterization is important to help choose the best available technique to extract and process the stones. The methodologies adopted in two different plants, according to their processed stones, are discussed hereafter. In addition, UPV and Knoop analyses were performed in order to establish the workability class of the two stones, and the classification developed in previous research works was applied. Subsequently, an analysis was conducted on the sludge resulting from the extraction and processing of blocks used for the production of slabs. A chemical analysis, a particle size analysis, a magnetic separation test, to obtain two fractions (metallic and mineral), and an SEM analysis of the two separated fractions were performed on the two sludges. This characterization was useful to understand whether the produced sludge could be recovered as by-products. The study will help stone producers to identify the best techniques for the extraction and processing of their stones, while obtaining less waste and less pollution

The invisible environmental impact of tourism in show caves: microplastic pollution in three Italian show caves

Show caves are the most important geological heritage in the world, a significant economic resource and unique ecosystems characterized by speleothems, particular species and important drinking water reserves, however, microplastic (MP) pollution in caves is poorly studied. The deposits of three NW Italian show caves were investigated: for each cave, six sediment samples were collected along the tourist paths and one in a non-touristic area. MPs were identified and characterized using MUPL automated software, observed with and without UV light under a microscope, and verified under μFTIR-ATR. MPs were present in sediments of all examined caves: an average of 4300 MPs/kg were found along the tourist paths and of 2570 MPs/kg in the speleological zones. MPs less than 1 mm, fibre-shaped, polyesters and polyolefins dominated the samples suggesting that synthetic clothes are the main source of pollution in show caves. Our results highlight a high pollution of MPs in the examined show caves, despite the different touristic and environmental characteristics. The subterranean environment monitoring gives useful information to assess risks posed by MPs in show caves and consequently define strategies for the conservation and management of caves and natural resources

STONES SAWING SLUDGE AS BY-PRODUCT: characterization for a future recovery

The European Commission, as part of its Thematic Strategy on the prevention and recycling of waste, committed itself to tackle one of the issues around the waste definition, namely the distinction between waste and by-products. This definition has been outlined through the Communication on waste and by-product of the European Court of Justice (Brussels, 21.2.2007 COM(2007) 59 final COMMUNICATION FROM THE COMMISSION TO THE COUNCIL AND THE EUROPEAN PARLIAMENT). By-product is a substance or object, resulting from a production process, the primary aim of which is not the production of that item. By-products can come from a wide range of business sectors, and can have very different environmental impacts. If there is a possibility that the material is in fact not useable, because it does not meet the technical specifications that would be required for its use, then it should continue to be considered as a waste. The status of waste protects the environment from the potential consequences of this uncertainty. If it subsequently happens that a use is found for the waste in question then it will lose its status of waste and it will be considered a by-product. An incorrect classification could be the cause of environmental damage or unnecessary costs for business. For this purpose a characterization of sludge coming from different plants of stone processing was carried out for a better classification of the materials in view of a future recovery. The different stones cutting processes considered for this study are: gangsaw, diamond blade and diamond wire. The cut materials are granites, gneisses, and other stones mainly of silicatic nature. The tests performed on the sawing sludge are the following: particle size analysis, chemical analysis, wet magnetic separation, diffraction and SEM analysis. The study performed is useful for evaluating the possible reuses of the products coming from the magnetic separation: the metal fraction, and the mineral one. In order to avoid a subsequent environmental degradation and to promote a technology innovation (sustainability and circular economy) a proactive waste management strategy trying to optimize on the one hand the processing to obtain reduced waste and the other to improve the process to obtain two reusable by-products was considered

Study of metal recovery from printed circuit boards by physical-mechanical treatment processes

The acceleration of the global production and consumption of electronics device and the concerns related to waste electrical and electronic equipment (WEEE) motivated this research. Printed circuit board (PCB) can be found in almost all type of electronic devices, making it an important component of WEEE. It has a heterogenous composition made of polymers, ceramic material, and metals. It contains heavy metals that can cause environmental impacts due to improper disposal. But on the other hand, there are elements with added value, such as copper, gold, silver, iron, aluminum and critical raw materials, such tantalum that can be recovered, making PCB scrap an economically attractive for recycling. The metal recovery can conserve natural resources, since it prevents new minerals from being extracted and it is a great contribution to the circular economy, removing the waste from its disposal and reinserts in the production cycle. The mechanical recycling of PCBs was studied through different operations, with the following sequence, comminution, granulometric classification, magnetic separation, gravity separation and electrostatic separation. The goal is to concentrate metals, especially copper, identifying the main elements obtained through cheaper processes to recycle e-waste. The PCB composition was initially carried out through the scanning electron microscope analysis. Then, it was shredded in a cutting mill and classified according to their grain size by sieving. Afterwards, a magnetic separation has been performed together with gravity and electrostatic separation of the non-magnetic fraction. The products obtained were observed with the macroscope to qualitatively assess the metallic content. The results obtained allowed to conclude that physical-mechanical techniques have high potential to produce a concentrate product with high added value. The application of magnetic separation proved to be efficient, as it enabled the recovery of high percentage of iron. In gravity separation, the metal recovery was satisfactory for the particle size -0.6 + 0.3 mm and for the particle size -1.18 + 0.6mm. In the recovery of metals by electrostatic separation the efficiencies obtained was really high the lower particle size (-0.3mm)

Characterization of marble weathering through pore structure quantitative analysis

Y Stone weathering is strongly controlled by the intrinsic properties of the stone and by its use. Previous studies demonstrate that the response to natural or artificial ageing processes of the rocks seems to be strongly influenced by the pore structure of the stone. A better understanding of this phenomenon is provided by the study and characterization of porosity and of the pore structure at different degrees of alteration. The analysis of the evolution of the decay leads to the evaluation of the durability of marble in facades, and more generally in buildings, as well as for the protection and recovery of artistic and architectural heritage.In this paper, we apply a methodology for the geometrical characterization of the pore structure to quantify alteration induced by natural weathering on marble slabs. The approach is based on the application of a path-finding algorithm to 2D binary images representative of thin sections of marble at different degrees of alteration. Through the identification of the paths within the porous domain, the methodology allows the characterization of the pore structure in terms of pore radius distribution along the identified paths. Analysis of the results demonstrate a good agreement between the degree of alteration of the pore structure and the corresponding variation of the physical and mechanical properties of the rock samples under investigation