1,721,102 research outputs found
Ultrasonic sound test on stone: comparison of indirect and direct methods under various test conditions
No full textIn order to choose the best ultrasonic measurement method, in transmission mode, on different rock categories (marbles, limestones and sandstones), a series of ultrasonic tests (with direct and indirect method, with different frequencies, on dried and saturated specimens, with control of pressure) have been executed, taking into account the petrographic characteristics of the stones tested. After the definition of accuracy in the measurement methods, the influence of climate factors, both in laboratory and in situ tests, has been evaluated. The comparisons between the results of ultrasonic tests obtained on saturated and dried specimens, with transducers with different frequencies of measure (54kHz, 33kHz, 250kHz), and by means of control of pressure, have been executed. The results obtained have been correlated with the results of other technological test executed on stone (non-destructive and destructive). From all the results obtained the indirect method with 33kHz frequency seems to be the most appropriated in expeditions measurements both in situ and in laboratory
Microplastic pollution in show cave sediments
Full text linkMicroplastic (MP) (plastics < 5mm) are a global issue, which has been widely found in marine and terrestrial environments, contaminating also remote areas, being them extremely mobile. However, MP pollution in underground environment, such as caves and karst aquifers, is still largely unknown. MPs can be ingested by hypogean animals and endanger the fragile ecosystems of the caves. Geologic features are the primary attraction of the show caves, and MPs can irreversibly damage speleothems deposited on them: they can directly damage speleothems, being incorporated into the cave formation growth, sometimes coloring them, or indirectly, by providing nutrients for acid-producing organisms that can dissolve limestone. Moreover, MPs can pollute karst aquifers which are open systems, even susceptible to contamination by surface pollutants. Therefore, the areas above the caves must also be monitored.
To improve the current knowledge of MP pollution, the sediments of three different show caves in Italy (Bossea, Borgio Verezzi and Toirano caves) were sampled and investigated. A new detection technique, based on the optimization of investigation tests used on different kind of sediments was used (Balestra & Bellopede, 2022). MPs were extracted from sediments via density separation and subjected to organic matter removal. Filters were observed with and without UV light under a microscope, exploiting the MPs fluorescence given by the fluorescent whitening agents additives, before and after organic matter removal. MPs were characterized with visual identification and described using the standardized size and colour sorting system (SCS) (Crawford & Quinn, 2016). In Bossea cave, an average of 4390 items/kg dry weight was calculated for the touristic zone and 1600 items/kg dry weight for the speleological/research section of the cave. Fibre (84.9%) was the most abundant shape, suggesting that synthetic clothes of visitors are the main source of MPs pollution in cave. Most MPs were smaller than 1 mm, accounting for 85.4%, of which 58.4% were shorter than 0.5 mm. The highest MP abundance was fluorescent under UV light (87.7%); however, 12.3% of the MPs observed on filters were not fluorescent. Most fluorescent fibres were transparent (84%), whereas blue (46.1%) and black (22.4%) fibres were more common for the non-fluorescent ones. Borgio Verezzi and Toirano caves sediment samples will be used to test an automated counting software designed by a team work of Politecnico di Torino.
Our results highlight the presence of MPs in show caves, and we provide a valid non-invasive and non-expensive analytical technique for the preparation and isolation of MPs from cave sediments, giving useful information for evaluating the environmental risks posed by MPs in caves
Durability tests on sandstones
No full textThe sandstone is widely used as cladding stone, even in historic building. Its decay its commonly associated with the action of salts or with sulphation in polluted conditions. In fact, in many cases, the decreasing of mechanical properties under the action of salt crystallization and SO2 is higher than the one induced by frost and by thermal shock action. The results of durability tests performed in laboratory or coming from literature data, referred to sand-stones even with differences in petrographic and mineralogical properties, are analysed. Three durability tests are object of this study: the determination of resistance to salt crystallisation according to EN 12370, the resis-tance to ageing by SO2 action in the presence of humidity according to EN 13919, the determination of frost resistance according to EN 12371. The evaluation of the decay degree has been performed by means of de-structive and non destructive tests, with further investigation than required by the standards, to evaluate which property (physical or mechanical) is more suitable to detect the weathering on this kind of rock. Often the method to evaluate the decay forecast by the standards does not underline the real alteration occurred in the stone sample, while other measurements of different characteristics do it. For example the mass weighing difference is not always satisfactory to appreciate the decay of the stone after salt crystallization while the water absorption, well correlated with the physical mechanical characteristics of the stones, together with visual inspection, is a good index of the decay for a distinction, in terms of durabil-ity, between different sandstones even of a same geological distric
The effect of water on the strength of building stones
No full textProblem statement: Water is one of the main causes of stone decay and the presence of water alone inside a stone could cause a decrease in its mechanical strength. In order to study the effect of water on the mechanical strength of stones, three Italian stones, which have historically been used for balconies, have been studied: Pietra di Luserna, Pietra Verde Argento and Pietra di Courtil. Approach: A comparison has been made between the effect of artificial ageing, by means of freeze and thaw cycles (where the increase in pores produced by iced water mechanically weakens the stone) and the effect of saturation on sound specimens subjected to flexural strength tests. Results: The results have shown that the three stones are very resistant to freeze and thaw cycles, but their mechanical strength decreases in wet condition. Conclusion/Recommendations: On the basis of the obtained results, it can be stated that mechanical strength values in wet conditions should be considered, in the planning of structural stonework for exterior use. As demonstration the case of a Pietra di Luserna balcony, where fault is occurred, a is reporte
The ultrasonic technique for in situ investigations on stones: suggestions for uses
No full textThe Ultrasound Pulse Velocity (UPV) is one of the main non destructive techniques to detect both in laboratory and
in situ the stone decay and many international papers of the recent years deal with its application. This technique
is often executed in laboratory, where the possibility to keep constant the environmental and test conditions are a
guarantee of the reliability of the results.
It is known in fact the UPV are mainly conditioned by the following factors:
- the characteristics of the stone tested (not only petrographic properties such as texture and structure, but even
specimen dimension and water content);
- the transducers features such as frequency, divergence angle , near field and wavelength;
- external climate factors such as environmental temperature, humidity.
In spite of the many factors affecting the measurements, UPV performed in laboratory is well correlated with
mechanical strength of the stone , with its porosity and, as consequence, it is a reliable technique to detect the
durability of a stone.
On the other side, for in situ UPV test it is important to take into account that the measurement uncertainty is
affected by the unknown water content in the stone. From tests performed on different rocks (marble, limestones,
travertines, granites, gneiss, schists , sandstones) , the ratios between UPV tested in dry and saturated conditions
can be > 1 or < 1 depending on the porosity .
On the base of the results obtained, in this paper suggestions for UPV measurements in situ have been advanced
concerning: the importance of the petrographic characterization of the stone in order to choose the suitable mea-
surement frequency; the correct choice of transducers frequencies; the use of a reference slab, with a known UPV
in dry conditions, to be exposed in the investigated site some days before the in situ tests, in order to appreciate the
UPV variation due to climate factors
Aggregates from tunnel muck treatments. Properties and uses
No full textTunnel muck should be considered as a valuable resource: if it is managed and treated correctly, it can be used for different purposes. This would lead not only to environmental benefits but also those of an economic nature. This work is part of the REMUCK project and it has the purpose of evaluating the effects of different treatments on different types of excavated rock. Five case studies have been selected and, of these, two were excavated with TBM (the Torrent-La Thuile tunnel and the Brennero tunnel), one with EPB (the Turin underground railway) and two using traditional excavation methods (Turin underground railway station and the Omegna tunnel). Tests have been carried out in the laboratory on both the muck in its natural state and on muck treated in two different plants (a mobile plant and a fixed plant) in order to characterise the aggregates from the shape and mechanical resistance points of view (according to EN 933-3 and EN 1097-2, respectively). The results of these tests have been compared with the threshold values foreseen in a muck management plan for a tunnel in Switzerland in order to verify the quality of the treatments the recycled aggregates were subjected to. This has made it possible to evaluate the suitability of the treatments, on the basis of the foreseen types of use, and to propose alternative working schemes for the nonconforming case
Materiali lapidei: proprietà tecniche, loro significato e relative prove di laboratorio - Massa volumica apparente e porosità
Full text linkExplorations in the dark continent: Did microplastics and microfibres get here before us?
Full text linkMicroplastic and microfibre pollution is a global concern, however, karst areas remain understudied. Because of
their properties, these anthropogenic microparticles are particularly hazardous, and easily transportable,
reaching also remote areas. The underground world, called also dark continent, is a treasure of information, and
remained the last frontier of terrestrial exploration: many parts of the underground world have not yet been
accessed. In the hypogeal environments, pollution is closely linked to the connections between surface and
subterranean habitats, the hydrodynamics of the aquifer, geology, and local environmental conditions. This
study aims to investigate, for the first time, the presence of microplastics and microfibres in unexplored caves,
revealing how human activity could indirectly impact even the uncontaminated environments of the dark
continent. Together with speleologists, we collected and investigated sediment samples from unexplored caves of
the Abruzzo Region, Italy. Examined anthropogenic microparticles were counted and characterized by composition, size, shape, fluorescence, and colour, via microscopy and spectroscopy. Microplastic concentrations
resulted low or absent, moreover, natural and regenerated microfibres ones were higher. Fibre-shape was the
most common. Most of the microparticles were clear and fluorescent under UV light. Pollution sources in this
area likely include atmospheric deposition, nearby human activities, roads, and garbage. These results highlight
anthropogenic microparticle pollution exists in unexplored karst caves, which could impact subterranean habitats, species, and water resources. Given the link between surface and underground karst environments, more
monitoring and protection are needed. This work encourages speleologists to collect samples during explorations too, as these rarely studied environments offer crucial insights into karst systems, potential threats, and conservation needs. Future long-term studies will clarify pollutant sources, transport, and effects on ecosystems
The Use of Tunnel Muck as Industrial Raw Material:Two Case-Studies
No full textThe re-use of rock as an industrial material requires more treatments than those foreseen for the reuse of muck as an aggregate for concrete and for road construction. The treatments always start with comminution, which has the goal of liberating the rock-forming minerals. Liberation is achieved with the appearance of grains which are composed of only one mineral. The subsequent treatment steps are based on the physical-mechanical-chemical properties of the different minerals, that is, density, magnetic susceptibility, wettability etc. Magnetic separation and flotation, the two techniques examined in this research, are the two most common techniques used in industrial mineral production plants. The mucks that were analysed are from the Omegna and Brennero tunnels, both of which are granitic rocks with different textures. From the analysis and comparison of the preliminary treatment results, it has been possible to optimise the treatment method. Petrographic, mineralogic and firing tests have been conducted to evaluate the obtained results. High-gradient magnetic separation (HGMS) on defined grain sizes appears to be suitable to obtain a product with a high feldspar-quartz content which could be used in the ceramic fiel
The Influence of the Climatic Factors on the Decay of Marbles: an Experimental Study
Full text linkStone 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
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