The Influence of the Climatic Factors on the Decay of Marbles: an Experimental Study

Stone decay is affected by the influence of climatic factors. In particular marble degradation, that could be expressed by decohesion and /or bowing, is mainly due to the action of temperature and water (rains and relative humidity). In this work non destructive and destructive tests have been performed to evaluate the decay of marble slabs subjected both to natural exposition and to artificial ageing tests (Lab - Bow test). Measurements of Ultrasonic Pulse Velocities (UPV) and bowing have been executed periodically on marble slabs exposed for a period of four years as preliminary field tests. On the base of this work an integrated test methodology to monitoring and previewing the behaviour of façade slabs have been set up. The methodology has been applied on the marble façade of modern building of centre Italy and consists of in situ and laboratory tests. In laboratory a destructive test (flexural strength) has been added to the non destructive tests to evaluate the decay before and after cycles of an ageing test. The results of the analysis, show an evaluative trend of the decay, though it changes its slope after 25 cycles of the ageing test. Moreover this work confirms the effectiveness of the employed non destructive tests and their god correlation with the mechanical tests

Microplastic pollution in karst areas: a threat to caves, groundwater and protected species and habitats

Microplastics (MPs) are a global problem, contaminating also remote areas, being them extremely mobile. However, MP pollution is poorly known in karst areas, especially in subterranean environment. Groundwater in karst aquifers constitutes about 25% of the global drinking water sources and karst caves are one of the most important and well-known geological features in the world, fragile sites with an exceptional scientific value, rich in endemic fauna, an environmental and cultural heritages, as well as an important economic resource. MPs can endanger the fragile subterranean ecosystems, be ingested by animals, irreversibly damage speleothems and paleontological/archaeological findings depositing on them and pollute karst aquifers. Extending the research started for the Italian project PRIN SHOWCAVE [1], the aim of this study is to investigate and monitor MP pollution in karst superficial and subterranean environments from a geological, biological and environmental point of view, in order to define strategies for protection and conservation purposes. A new detection technique has been developed to study cave sediments [2], subsequently adapted to the different studied matrices. Samples from different karst areas of Italy were collected and investigated. The sediments of three show caves were analyzed, highlighting the presence of MPs and the damaging of speleothems and paleontological remains. Superficial and underground water samples of the Bossea karst system (Piedmont) were analyzed, showing MP pollution in all examined waters, underlining the importance of the entire aquifer karst systems monitoring, even susceptible to contamination by surface pollutants. Different water environment samples of springs and caves in Carso system (Friuli-Venezia Giulia) were collected and will be analyzed to verify the MP pollution in different habitats, hosting particularly protected species such as Proteus anguinus. Sediment samples in a not jet explored caves will be collected to verify the MPs pollution even in underground environments not directly affected by human presence

Stone roofing in the Aosta Valley, Italy: Technical properties and durability of traditional Lithotypes

The Aosta Valley Region has promulgated in 1990 a law to partially finance stone roofs to the owners of houses in the historic centers of the valley, provided that the stone material chosen was suitable for this use. This suitability was certified by physical, mechanical and durability tests. More than twenty years ago, roofing slabs were extracted in north-western Alps mainly from schistose rocks. In recent time instead roofing slabs, according to global market, have an international origin. All the traditional stones tested showed excellent technical features according to the local legislation on roof slates. One of these traditional stones is a phyllite whose trade name is “Porfiroide” having the best physical and mechanical properties compared to the other kinds of traditional stones, but with a high standard deviation in the results of flexural strength performed after the freeze and thaw cycles. In the roofing installed 40 years ago, despite their best technical features, the “Porfiroide” roof slabs show a poor state of conservation with widespread detachments, fractures, growth of mosses and lichens, variations in colours. Otherwise, stones with a lower value of flexural strength and higher water absorption instead show good behaviour in the roofing in situ and also in terms of colour change. Evidently the only characterisation of the stone materials is not sufficient but it must be associated to a on-site verification, comparing each slab to be installed with a reference sample, part of the sample submitted to the tests, and to a control on site of the resistance of the stones to degradation

Ornamental stone cutting processing and sludge production evaluation with the goal of ending waste.

The End-of-waste concept was introduced by the ‘Thematic Strategy on the prevention and recycling of waste’ adopted by the European Commission, in which it proposed to specify the conditions for the cessation of waste status as part of the revision of the Waste Framework Directive (Directive 2008/98/EC). The Directive states that a waste shall lose its status if it is submitted to a recovery operation (including recycling) and comply with specific eligibility criteria. The strategic goal of the End-of-waste is to promote recycling, helping to ensure a high level of environmental protection through the reduction of the consumption of critical raw materials and the quantities of waste destined for disposal. In the mining sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also identifying the best available cutting technique to be used on the basis of the physical, chemical and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge and producing less waste. In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out. Three types of analysis were conducted in parallel. The first concerns the characterization of the stones and the choice of the type of cutting machine. The analyses carried out were: petrographic analysis, compression strength, flexural strength, apparent density and water absorption. Also ultrasonic pulse velocity (UPV) and Knoop analyses were performed in order to establish the workability class of the stones, and their classification in accordance with previous research works (EASE R3). The second analysis involves calculating the amount of sludge produced in the three different cutting technologies, taking into account the same block characteristics. The third analysis was conducted on the sludge resulting from the processing of blocks cut into slabs. A comparison was carried out on the quality of the sludge produced, or type and quantity of metals present, taking into account the three different technologies. The tests carried out were: chemical analysis, magnetic separation test and SEM analysis of the metal fraction. The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a good efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy

Ornamental Stone Cutting Processing and Sludge Production Evaluation with the Goal of Ending Waste

In the quarry sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also by identifying the best available cutting technique to be used on the basis of the physical, chemical, and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces, and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge, and producing less waste. In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out. Two types of analysis were carried out in parallel: evaluation of the stones workability and calculation of the amount of sludge produced in the three different cutting technologies and from the cutting of blocks. A comparison was carried out on the quality of the sludge produced, on type and quantity of metals present, taking into account the different cutting technologies. The performed tests were: chemical analysis, magnetic separation test, and SEM analysis of the metal fraction. The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a high-efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy

Marble Durability Assessment by Means of Total Optical Porosity and Adjacent Grain Analysis

The presence of pores, cracks and microcracks in marble is one of the main features that govern the processes of decay of this stone material and, although marble is characterised by a modest porosity, there is a clear correlation between the presence and movement of fluids, and the phenomena of alteration. Through the study of porosity, it is possible to better understand the phenomena of alteration and degradation in order to obtain useful information, not only in the field of modern building, but also for the protection and recovery of historical and artistic heritage goods. This study was conducted through the characterisation of parameters directly related with the degree of alteration of the materials: water absorption at atmospheric pressure (EN 13755), open porosity (EN 1936), flexural strength (EN 12372) and bowing (EN 16306 par. 8.2). The physical and mechanical measurements have been compared with the Total Optical Porosity method (TOP) and the Adjacent Grain Analysis (AGA) index (a suggested method to evaluate the marbles’ tendency to bow, in EN 16306 annex C); two different methodologies both based on image analysis. The purpose of this study is to demonstrate the effectiveness, for the assessment of marble durability, of the two techniques of microscopic image analysis, the first correlating to the grain shape and the second to the open porosity index. This was done by comparing the microscopic image analysis results with the physical and mechanical properties, both after artificial ageing and after ten years of natural ageing. The results obtained with the TOP method seem to represent the tendency to decay better than the AGA index. The comparison of image analysis of the thin sections, in different portions of the marble specimens, shows the development of degradation due to atmospheric agents, from the surface to the inside, of naturally aged specimens, confirming recent studies made on different marbles

Biocorrosion of speleothems in show caves: analysis of young speleothems exposed to two years of new LED lights

Speleothems in show caves are the most important attractions, however, they are often subjected to tourism-driven alterations, including corrosion due to CO2 increase, undersaturated water and photosynthetic biofilms. The so-called “lampenflora” is a community of photosynthetic microorganisms, mainly cyanobacteria, diatoms and green algae, but may also include mosses, ferns and higher plants. It develops on speleothems in show caves, following the installation of artificial lights, which allow the photosynthetic activity in an otherwise dark environment. The growth of the lampenflora causes physical, chemical and aesthetic damage to speleothems and changes the underground ecosystem, as it modifies the food chain and can therefore damage the organisms that naturally inhabit the cave itself. Moreover, the biochemical reactions given by the metabolic activity of microorganisms can release substances that lead to the deterioration of the rock, resulting in erosion and damage to speleological formations. Bossea cave, Piedmont, Italy, was opened to the public in 1874, and receives about 12,000 tourists/year. The cavity develops for about 2800 m in a tectonic contact between dolostone, carbonate rocks and metavolcanics and it is crossed by a subterranean river. Different underground karst laboratories to study hydrogeology, climatology, radon activity and subterranean biology are located in the cave, managed by S.O. Bossea CAI, the DIATI of the Politecnico di Torino, and Biologia Sotterranea Piemonte – Gruppo di Ricerca. In the Bossea cave, the presence of lampenflora and biocorrosion on speleothems along the tourist path was previously documented. A new LED lights system was installed in 2021, which should allow a slowdown of the phenomenon of lampenflora. This study aims at observing the growth of lampenflora with the new LED lamps, evaluating changes in calcite crystal habits over time. A homogenous slab of speleothem recently formed as a patina on a cover of the central underground laboratory instrumentation was collected, divided into several parts and observed with a Scanning Electron Microscopy (SEM). After, 17 small slab parts were placed along the tourist path in six different areas, from one to seven parts per point, positioned with different inclinations, where they remained for two years. These areas were chosen taking into account the presence of lampenflora due to the previous halogenic lamps. Then, the samples were collected to verify the degree of biocorrosion. For each sample, different points were analysed with SEM and classified according to a predetermined index

CIRCULAR ECONOMY IN THE EXTRACTIVE SECTOR

The mining and the quarry sector shares the need to enhance the by-products as one of the most effective tools to limit waste production. This has the aim of minimizing the environmental cost of raw materials upstream production chains and to support research and technological innovation, providing opportunities for growth, competitiveness and creation of added value for important sectors. The exploitation of mines, quarries and the related treatment plants produces large quantities of "tailings". The by-product can be reused for different purposes within the construction supply chain (construction of road embankments, concrete, pre-mixed products, fillers etc.) thanks to their shape, size, physical and petrographic characteristics. For this reason it is essential to enhance the use of by-products of the extractive industry according to the last European regulation and implementing the National ones. In particular, the main crucial points in extractive industry to be faced and improved applying the Circular Economy approach are: - mining/quarry tailings. - sawing sludge from ornamental stone industry. - waste water from aggregate processing. The “circular approach” in the extractive industry is possible considering by-products in zero-waste supply chains as valuable secondary raw materials since the very beginning of every operation planning. A change in this vision is needed to sustain, also by means of proper indicator, an even more efficient circular economy