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Francesco Sauro - One of the best experts on this subject based on the ideXlab platform.
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genesis of giant sinkholes and caves in the Quartz Sandstone of sarisarinama tepui venezuela
Geomorphology, 2019Co-Authors: Francesco Sauro, Jo De Waele, Marco Mecchia, Leonardo Piccini, Cristina Carbone, Andrea Columbu, Luca Pisani, Freddy VergaraAbstract:Abstract Quartz Sandstone of the Sarisarinama massif in Venezuela hosts the world biggest collapse dolines in Quartz-rich lithologies, with volumes up to some millions of cubic meters. Due to extremely complex logistics required to reach the massif, the genesis of these depressions and of the underlying caves has never been studied in detail. The lack of field campaigns and extended data has fostered a decade-long scientific debate on whether their origin was due to epigenic or hypogenic processes. This study integrates petrological, structural and hydrochemical observations, including analyses of silica concentration, pH, conductivity of surface and cave waters (EC), to investigate the speleogenetic processes acting underground. Petrographic and compositional analyses of the host rock (Mataui Formation) show that in the Sarisarinama region Quartz Sandstones are regularly characterized by clay interlayers with significant content of pyrophyllite and kaolinite and minor amount of iron hydroxides. Compared to surface waters, subsurface infiltration along vertical fractures and fault planes show enrichment in silica, higher pH and lower EC, confirming that chemical weathering is effective underground provoking intergranular silica dissolution along structural discontinuities. The weathering of the clay and iron hydroxide interlayers guides the speleogenesis, weakening specific stratigraphic levels and causing the collapse and fragmentation of the more resistant Quartz Sandstone strata. The initial void, created by piping of the loose sand released by Quartz Sandstone weathering, can migrate upwards by means of roof and wall breakdown; this chain of events eventually triggers a collapse at the surface, which generates a circular or squared sinkhole. The weathering acts mainly along the dominant fracture networks, showing a clear guidance by regional tectonics. These speleogenetic controls rule out the hypothesis of a hypogenic origin of the simas, suggesting a primary role of long-term epigenic chemical weathering and mechanical erosion guided by joints, weak clay and iron hydroxide interlayers, followed by subsequent massive collapses.
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a hybrid model to evaluate subsurface chemical weathering and fracture karstification in Quartz Sandstone
Journal of Hydrology, 2019Co-Authors: Marco Mecchia, Francesco Sauro, Leonardo Piccini, Andrea Columbu, Jo De WaeleAbstract:Abstract A hybrid numerical, finite differences and semi-analytical/empirical model has been developed to evaluate the spatial and time scale of chemical weathering along a fracture in Quartz Sandstones. The model is based on the diffusion transport occurring from the bedrock mass toward the fracture walls driven by the SiO2 concentration gradient between water in the bedrock pores (high silica content) and water flowing in the fracture (low silica content). Because of molecular diffusion, intergranular water becomes undersaturated with respect to silica. This promotes dissolution of Quartz at grain boundaries and results in a porosity profile decreasing from the fracture walls toward the rock interior. Bedrock individual grains are released and gradually removed by the water flowing into the fracture when a critical value of porosity is reached (Grain Release Threshold, GRT): this process drastically increases the fracture enlargement rate. The model outcomes establish a minimum time of 90 ka to reach the GRT. This time is independent of length, aperture and dip of the fracture, but is controlled by parameters such as the initial fracture aperture, water temperature, Quartz grain size, and initial bedrock porosity. It is attested that the water flowing in the fracture remains undersaturated with respect to silica over very long timescales (in the order of 105 years) and over very long flow paths. In turn, this suggests that the extremely slow reaction between Quartz and water is the key-factor for the formation of subterranean karst-like features in Quartz Sandstone, otherwise silica saturation would be reached after short distances and deep weathering in this lithology would be prevented. Finally, the model outcomes were compared to field data from the Gran Sabana caves (Venezuela) and other Quartz Sandstone weathering landforms elsewhere, showing that dissolution/diffusion in the rock matrix is a reliable mechanism for the formation of these peculiar karst-like features.
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Quartzite and Quartz Sandstone caves of south america
2019Co-Authors: Augusto S Auler, Francesco SauroAbstract:Abstract South America is well endowed with Quartzite outcrops and caves, especially in southern Venezuela and along eastern Brazil. Quartzite caves may display branchwork, anastomotic and network patterns similar to carbonate caves, showing strong geological control associated with layers less resistant to erosion. Vertical caves close to scarps develop along unloading joints and may be at least in part tectonic features. Cave initiation involves loosening of Quartz grain by intergranular dissolution or chemical removal of silica-rich matrix, kaolinite, or mica. Mechanical removal of Quartz residue may enlarge cave passages once there is an opened evacuation route. Microbial mediation may play a role, especially in generating unique stromatolitic speleothems. Slow rates of dissolution, low content of silica in the groundwater and the old age of the bedrock favor a long term evolution for Quartzite speleogenesis, perhaps orders of magnitude slower than in carbonate settings.
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exploring the microbial diversity featuring the geochemical complexity of the Quartz Sandstone cave imawari yeuta auyan tepui venezuela
17th International Congress of Speleology, 2017Co-Authors: Daniele Ghezzi, Francesco Sauro, Leonardo Piccini, Freddy Vergara, Hosam M Zowawi, Peiying Hong, Martina Cappelletti, Davide Zannoni, Jo De WaeleAbstract:In the last three years, one of the longest Quartz-Sandstone caves, Imawari Yeuta, has been explored in the Precambrian rocks of the Auyan Tepui massif in Venezuela. The uniqueness of this Quartz-Sandstone cave resides in its great age (estimated over 30 Ma) and its complete isolation from anthropogenic activities. Therefore, subsurface ecosystems might have been preserved from contamination and possible subsequent alteration. The cave contains a high level of microbial activity as demonstrated by the presence of silica stromatolite-like speleothems, biologically mediated sulphate-phosphate deposits and lakes covered by patinas of violaceous or other colourful biofilms. The high diversity of the environments, in terms of mineralogical substrate and geochemistry of the waters, suggests that niche-differentiation of the microbial communities could be mainly controlled by the specific chemical characteristics of each site rather than by light attenuation, i.e., the distance from the entrances of the cave toward the dark zones. To investigate this possibility, we characterised the microbial community composition in 17 samples collected during the expeditions of 2014 and 2016 to the cave system. In particular, the next-generation sequencing (NGS) approach was performed by using Illumina MiSeq technology targeting the 16S rRNA gene. The acquired data have then been correlated with geochemical (water pH, EC, major and minor elements) and mineralogical (predominant and secondary minerals) information from each sampling site. The results showed that the cave hosts three main types of microbial communities, each of these characteristic of a specific environment dominated by silica (crystalline or amorphous), iron hydroxides or hydrated sulphate-phosphates.
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structural and lithological guidance on speleogenesis in Quartz Sandstone evidence of the arenisation process
Geomorphology, 2014Co-Authors: Francesco SauroAbstract:A detailed petrographic, structural and morphometric investigation of different types of caves carved in the Quartz–Sandstones of the “tepui” table mountains in Venezuela has allowed identification of the main speleogenetic factors guiding cave pattern development and the formation of particular features commonly found in these caves, such as funnel-shaped pillars, pendants and floor bumps. Samples of fresh and weathered Quartz–Sandstone of the Mataui Formation (Roraima Supergroup) were characterised through WDS dispersive X-ray chemical analyses, picnometer measurements, EDAX analyses, SEM and thin-section microscopy. In all the caves two compositionally different strata were identified: almost pure Quartz–Sandstones, with content of silica over 95% and high primary porosity (around 4%), and phyllosilicate-rich Quartz–Sandstone, with contents of aluminium over 10% and low primary porosity (lower than 0.5%). Phyllosilicates are mainly pyrophyllite and kaolinite. SEM images on weathered samples showed clear evidence of dissolution on Quartz grains to different degrees of development, depending on the alteration state of the samples. Grain boundary dissolution increases the rock porosity and gradually releases the Quartz grains, suggesting that arenisation is a widespread and effective weathering process in these caves. The primary porosity and the degree of fracturing of the Quartz–Sandstone beds are the main factors controlling the intensity and distribution of the arenisation process. Weathering along iron hydroxide or silt layers, which represent inception horizons, or a strata-bounded fracture network, predisposes the formation of horizontal caves in specific stratigraphic positions. The loose sands produced by arenisation are removed by piping processes, gradually creating anastomosing open-fracture systems and forming braided mazes, geometric networks or main conduit patterns, depending on the local lithological and structural guidance on the weathering process. This study demonstrates that all the typical morphologies documented in these Quartz–Sandstone caves can be explained as a result of arenisation, which is guided by layers with particular petrographic characteristics (primary porosity, content of phyllosilicates and iron hydroxides), and different degrees of fracturing (strata-bounded fractures or continuous dilational joints).
Jo De Waele - One of the best experts on this subject based on the ideXlab platform.
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genesis of giant sinkholes and caves in the Quartz Sandstone of sarisarinama tepui venezuela
Geomorphology, 2019Co-Authors: Francesco Sauro, Jo De Waele, Marco Mecchia, Leonardo Piccini, Cristina Carbone, Andrea Columbu, Luca Pisani, Freddy VergaraAbstract:Abstract Quartz Sandstone of the Sarisarinama massif in Venezuela hosts the world biggest collapse dolines in Quartz-rich lithologies, with volumes up to some millions of cubic meters. Due to extremely complex logistics required to reach the massif, the genesis of these depressions and of the underlying caves has never been studied in detail. The lack of field campaigns and extended data has fostered a decade-long scientific debate on whether their origin was due to epigenic or hypogenic processes. This study integrates petrological, structural and hydrochemical observations, including analyses of silica concentration, pH, conductivity of surface and cave waters (EC), to investigate the speleogenetic processes acting underground. Petrographic and compositional analyses of the host rock (Mataui Formation) show that in the Sarisarinama region Quartz Sandstones are regularly characterized by clay interlayers with significant content of pyrophyllite and kaolinite and minor amount of iron hydroxides. Compared to surface waters, subsurface infiltration along vertical fractures and fault planes show enrichment in silica, higher pH and lower EC, confirming that chemical weathering is effective underground provoking intergranular silica dissolution along structural discontinuities. The weathering of the clay and iron hydroxide interlayers guides the speleogenesis, weakening specific stratigraphic levels and causing the collapse and fragmentation of the more resistant Quartz Sandstone strata. The initial void, created by piping of the loose sand released by Quartz Sandstone weathering, can migrate upwards by means of roof and wall breakdown; this chain of events eventually triggers a collapse at the surface, which generates a circular or squared sinkhole. The weathering acts mainly along the dominant fracture networks, showing a clear guidance by regional tectonics. These speleogenetic controls rule out the hypothesis of a hypogenic origin of the simas, suggesting a primary role of long-term epigenic chemical weathering and mechanical erosion guided by joints, weak clay and iron hydroxide interlayers, followed by subsequent massive collapses.
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a hybrid model to evaluate subsurface chemical weathering and fracture karstification in Quartz Sandstone
Journal of Hydrology, 2019Co-Authors: Marco Mecchia, Francesco Sauro, Leonardo Piccini, Andrea Columbu, Jo De WaeleAbstract:Abstract A hybrid numerical, finite differences and semi-analytical/empirical model has been developed to evaluate the spatial and time scale of chemical weathering along a fracture in Quartz Sandstones. The model is based on the diffusion transport occurring from the bedrock mass toward the fracture walls driven by the SiO2 concentration gradient between water in the bedrock pores (high silica content) and water flowing in the fracture (low silica content). Because of molecular diffusion, intergranular water becomes undersaturated with respect to silica. This promotes dissolution of Quartz at grain boundaries and results in a porosity profile decreasing from the fracture walls toward the rock interior. Bedrock individual grains are released and gradually removed by the water flowing into the fracture when a critical value of porosity is reached (Grain Release Threshold, GRT): this process drastically increases the fracture enlargement rate. The model outcomes establish a minimum time of 90 ka to reach the GRT. This time is independent of length, aperture and dip of the fracture, but is controlled by parameters such as the initial fracture aperture, water temperature, Quartz grain size, and initial bedrock porosity. It is attested that the water flowing in the fracture remains undersaturated with respect to silica over very long timescales (in the order of 105 years) and over very long flow paths. In turn, this suggests that the extremely slow reaction between Quartz and water is the key-factor for the formation of subterranean karst-like features in Quartz Sandstone, otherwise silica saturation would be reached after short distances and deep weathering in this lithology would be prevented. Finally, the model outcomes were compared to field data from the Gran Sabana caves (Venezuela) and other Quartz Sandstone weathering landforms elsewhere, showing that dissolution/diffusion in the rock matrix is a reliable mechanism for the formation of these peculiar karst-like features.
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exploring the microbial diversity featuring the geochemical complexity of the Quartz Sandstone cave imawari yeuta auyan tepui venezuela
17th International Congress of Speleology, 2017Co-Authors: Daniele Ghezzi, Francesco Sauro, Leonardo Piccini, Freddy Vergara, Hosam M Zowawi, Peiying Hong, Martina Cappelletti, Davide Zannoni, Jo De WaeleAbstract:In the last three years, one of the longest Quartz-Sandstone caves, Imawari Yeuta, has been explored in the Precambrian rocks of the Auyan Tepui massif in Venezuela. The uniqueness of this Quartz-Sandstone cave resides in its great age (estimated over 30 Ma) and its complete isolation from anthropogenic activities. Therefore, subsurface ecosystems might have been preserved from contamination and possible subsequent alteration. The cave contains a high level of microbial activity as demonstrated by the presence of silica stromatolite-like speleothems, biologically mediated sulphate-phosphate deposits and lakes covered by patinas of violaceous or other colourful biofilms. The high diversity of the environments, in terms of mineralogical substrate and geochemistry of the waters, suggests that niche-differentiation of the microbial communities could be mainly controlled by the specific chemical characteristics of each site rather than by light attenuation, i.e., the distance from the entrances of the cave toward the dark zones. To investigate this possibility, we characterised the microbial community composition in 17 samples collected during the expeditions of 2014 and 2016 to the cave system. In particular, the next-generation sequencing (NGS) approach was performed by using Illumina MiSeq technology targeting the 16S rRNA gene. The acquired data have then been correlated with geochemical (water pH, EC, major and minor elements) and mineralogical (predominant and secondary minerals) information from each sampling site. The results showed that the cave hosts three main types of microbial communities, each of these characteristic of a specific environment dominated by silica (crystalline or amorphous), iron hydroxides or hydrated sulphate-phosphates.
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source and genesis of sulphate and phosphate sulphate minerals in a Quartz Sandstone cave environment
Sedimentology, 2014Co-Authors: Francesco Sauro, Nicola Tisato, Tomaso R R Bontognali, Stefano M. Bernasconi, Jo De Waele, Ermanno GalliAbstract:Gypsum (CaSO4·2H2O), alunite (KAl3(SO4)2(OH)6), and rare phosphate–sulphate sanjuanite Al2(PO4)(SO4)(OH) 9(H2O) and rossiantonite (Al3(PO4)(SO4) 2(OH)2(H2O)14) have recently been identified as secondary mineral deposits in different Quartz-Sandstone caves in the Gran Sabana region, Venezuela. Due to the extended time scale required for speleogenesis in the hard and barely soluble Quartz-Sandstone lithology, these caves are considered to be as old as 20 to 30 My. The study of these peculiar secondary mineral deposits potentially reveals important insights for understanding the interaction between deep, superficial and atmospheric processes over thousands to perhaps millions of years. In this study, chemical and petrographic analyses of potential host rock sources, sulphur and oxygen isotope ratios, and meteorological, hydrological and geographical data are used to investigate the origin of sulphates and phospho–sulphates. The results suggest that the deposition of sulphates in these caves is not linked to the Quartz-Sandstone host rock. Rather, these mineral deposits originate from an external atmospheric sulphate source, with potential contributions of marine non-sea salt sulphates, terrestrial dimethyl sulphide and microbially reduced H2S from the forests or peatbogs within the watershed. Air currents within the caves are the most plausible means of transport for aerosols, driving the accumulation of sulphates and other secondary minerals in specific locations. Moreover, the studied sulphate minerals often co-occur with silica speleothems of biological origin. Although this association would suggest a possible biogenic origin for the sulphates as well, direct evidence proving that microbes are involved in their formation is absent. Nonetheless, this study demonstrates that these Quartz-Sandstone caves accumulate and preserve allogenic sulphates, playing a yet unrecognized role in the sulphur cycle of tropical environments.
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Geochemistry of surface and subsurface waters in Quartz-Sandstones: significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela)
Journal of Hydrology, 2014Co-Authors: Marco Mecchia, Nicola Tisato, Francesco Sauro, Jo De Waele, Leonardo Piccini, Laura Sanna, Jesus Lira, Freddy VergaraAbstract:In situ measurements of discharge, pH, electric conductivity (EC), temperature, and SiO2 content have been carried out during five expeditions in the last 20 years on the summit plateaus, inside caves and along the rivers of the surrounding lowlands of three tepui massifs in Venezuela (Auyan, Roraima, and Chimanta). Additionally, detailed chemical analyses were performed on waters sampled in a newly discovered extensive Quartz-Sandstone cave system on the Auyan Tepui. Rock samples of the Quartz-Sandstone bedrock from different locations have been analysed to obtain their chemical composition with a wavelength dispersive X-ray fluorescence spectrometer. These data show that the majority of silica present in surface and subsurface water comes from dissolution of Quartz and only in minor amount from hydrolysis of other silicate minerals. Probably the presence of a hardened crust of iron hydroxides limits the dissolution of silica on the top surface of tepuis. Dissolution in the subsurface, instead, is more significant and causes, in the long term, the “arenisation” of the Quartz-Sandstone and its subsequent removal by mechanical erosion. On the other hand, waters flowing on the arkosic rock outcropping on the lowland below the tepuis obtain their high dissolved silica content mainly from hydrolysis of silicates. The morphological evolution of these table mountains appears thus to be controlled mainly by the underground weathering of the Quartz-Sandstone, with the opening of deep fractures (grietas) and the collapse of large underground horizontal cave systems. Scarp retreat, instead, seems to be related to the higher weathering rate of the more arkosic formations underlying the Quartz-Sandstones.
Sanjeev Kumar - One of the best experts on this subject based on the ideXlab platform.
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sustainable utilization of Quartz Sandstone mining wastes chloride and corrosion resistance
Journal of Materials in Civil Engineering, 2019Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep Shrivastava, Laszlo J CsetenyiAbstract:AbstractThere has been growing interest to reduce the use of conventional natural aggregates to promote sustainability in construction industry. In this study, Quartz Sandstones are substituted for...
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technical note on sorption and permeability of concrete containing rubber and Quartz Sandstone aggregates
Construction and Building Materials, 2017Co-Authors: Sanjeev Kumar, Ajay Sharma, Deepak Sherawat, Mohit Dutt, Ramesh Chandra GuptaAbstract:Abstract The presence of waste is a warning of overconsumption of materials and are not being used to its full potential. There has been a consistent decrease in environmental potential to absorb these wastes and a useful resource of matter and energy are lost due to the disposal of such wastes. The main problem associated is the excess production of wastes such as rubber and stones which could be utilised efficiently in many other ways. One of the sustainable utilisation of these wastes is by using them in the production of cement concrete. M30 concrete grade (water-cement ratio of 0.4) is designed as per Indian specifications with discarded tyre rubber as a partial replacement of fine aggregate and Quartz Sandstone as a partial replacement for coarse aggregates. The water absorption properties of concrete containing crumb rubber, Quartz Sandstone and a mixture of both were studied. Three Sandstone replacement levels (0%, 50% and 100%) are taken and five rubber replacement levels (0%, 2.5%, 5%, 7.5% and 10%) were considered for the study. Concrete having Quartz Sandstones as coarse aggregates and crumb rubber as fine aggregates are recommended to be used at 50% substitution level of Quartz Sandstone. The maximum rubber replacement in the same mix can be limited to 7.5% to maintain the increase in sorption rate below 15%.
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sulfuric acid resistance of Quartz Sandstone aggregate concrete
Journal of Materials in Civil Engineering, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep Shrivastava, Laszlo J CsetenyiAbstract:AbstractSandstone is a popular type of natural stone and is made up of collective grains of Quartz. India is one of the countries blessed with various types of Sandstones with appealing colors. Dem...
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long term studies on the utilisation of Quartz Sandstone wastes in cement concrete
Journal of Cleaner Production, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep ShrivastavaAbstract:Abstract Disposal of stone wastes has become one of the major environmental problems in the world. The use of marbles, granites and Sandstones as a building material has increased and the disposal of unused stones possess a severe threat to the society. Every year tonnes of stone wastes have been generated, and it was estimated that almost 25% of stone goes as wastes while processing and cutting them. Over the years, the quarrying area has expanded, and the use of modern machinery had led to the cutting of hardest of stones and exposing the soft underbelly of Sandstones. One of the possible solutions for the utilisation of these Sandstone wastes is to incorporate them into cement concrete as the replacement for natural coarse aggregates. This paper presents the results of experimental research to examine the suitability of Quartz Sandstone as a substitute for natural coarse aggregates in cement concrete. The Quartz Sandstone wastes were used in definite percentages and replaced for coarse aggregates from 0% to 100% at every 20% interval. The article presents with tests such as pull off strength, carbonation, sulphate attack, porosity and extended results of compressive strength, flexural strength. It was observed that the compressive strength, flexural strength and the sulphate attack resistance were lower than that of control concrete; but upto a certain level of replacement, they showed better resistance to pull off and carbonation. Also, the decrease in strength was found to be comparable to that of control specimens. It was concluded that there is a propitious future for the use of Quartz Sandstone wastes as a partial substitute for natural coarse aggregates in concrete, which can lead to a greater environmental and sustainable benefits.
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effective utilisation of Quartz Sandstone mining wastes a technical note on its thermal resistance
Journal of Cleaner Production, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep ShrivastavaAbstract:Sandstones are a sedimentary type of rock which is composed of Quartz, feldspar and other minerals. Since Quartz and feldspar are the most common minerals in the Earth's crust, they are found in most of the Sandstones irrespective of the region they occur. The formation of Sandstone results by sedimentation through air or wind followed by the compacting pressure of overlying deposits and cementation by precipitation of minerals. Rajasthan, being the largest state by area in India, is the major Sandstone producing region. Although Sandstones from the area are extensively used as roofing, flooring and paving material, the process of mining them generates an enormous amount of Sandstone wastes. These Sandstone wastes with Quartz-dominated elemental framework were utilised in an M30 grade concrete with water to cement ratio of 0.35 to overcome the landfilling problems and to reduce the use of depleting conventional coarse aggregates in the Vindhyan regions of Northern India. The concrete samples were investigated by scanning electron microscopy and thermogravimetry. The microscopic study revealed the presence of increased void fractions in the concrete samples containing Quartz Sandstone aggregates. These void fractions were found to enhance the thermal resistance of concrete based on the reduced weight loss upon heating them and also assumed to improve insulation properties by hindering the heat transfer in the material. The efficient utilisation of these Quartz Sandstone wastes in concrete can reduce the substantial amount of landfill that is used for dumping them and also provide a valuable source of supplementary aggregate used in the production of cement concrete contributing to the overall sustainability.
Sandeep Shrivastava - One of the best experts on this subject based on the ideXlab platform.
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sustainable utilization of Quartz Sandstone mining wastes chloride and corrosion resistance
Journal of Materials in Civil Engineering, 2019Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep Shrivastava, Laszlo J CsetenyiAbstract:AbstractThere has been growing interest to reduce the use of conventional natural aggregates to promote sustainability in construction industry. In this study, Quartz Sandstones are substituted for...
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sulfuric acid resistance of Quartz Sandstone aggregate concrete
Journal of Materials in Civil Engineering, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep Shrivastava, Laszlo J CsetenyiAbstract:AbstractSandstone is a popular type of natural stone and is made up of collective grains of Quartz. India is one of the countries blessed with various types of Sandstones with appealing colors. Dem...
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long term studies on the utilisation of Quartz Sandstone wastes in cement concrete
Journal of Cleaner Production, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep ShrivastavaAbstract:Abstract Disposal of stone wastes has become one of the major environmental problems in the world. The use of marbles, granites and Sandstones as a building material has increased and the disposal of unused stones possess a severe threat to the society. Every year tonnes of stone wastes have been generated, and it was estimated that almost 25% of stone goes as wastes while processing and cutting them. Over the years, the quarrying area has expanded, and the use of modern machinery had led to the cutting of hardest of stones and exposing the soft underbelly of Sandstones. One of the possible solutions for the utilisation of these Sandstone wastes is to incorporate them into cement concrete as the replacement for natural coarse aggregates. This paper presents the results of experimental research to examine the suitability of Quartz Sandstone as a substitute for natural coarse aggregates in cement concrete. The Quartz Sandstone wastes were used in definite percentages and replaced for coarse aggregates from 0% to 100% at every 20% interval. The article presents with tests such as pull off strength, carbonation, sulphate attack, porosity and extended results of compressive strength, flexural strength. It was observed that the compressive strength, flexural strength and the sulphate attack resistance were lower than that of control concrete; but upto a certain level of replacement, they showed better resistance to pull off and carbonation. Also, the decrease in strength was found to be comparable to that of control specimens. It was concluded that there is a propitious future for the use of Quartz Sandstone wastes as a partial substitute for natural coarse aggregates in concrete, which can lead to a greater environmental and sustainable benefits.
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effective utilisation of Quartz Sandstone mining wastes a technical note on its thermal resistance
Journal of Cleaner Production, 2017Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep ShrivastavaAbstract:Sandstones are a sedimentary type of rock which is composed of Quartz, feldspar and other minerals. Since Quartz and feldspar are the most common minerals in the Earth's crust, they are found in most of the Sandstones irrespective of the region they occur. The formation of Sandstone results by sedimentation through air or wind followed by the compacting pressure of overlying deposits and cementation by precipitation of minerals. Rajasthan, being the largest state by area in India, is the major Sandstone producing region. Although Sandstones from the area are extensively used as roofing, flooring and paving material, the process of mining them generates an enormous amount of Sandstone wastes. These Sandstone wastes with Quartz-dominated elemental framework were utilised in an M30 grade concrete with water to cement ratio of 0.35 to overcome the landfilling problems and to reduce the use of depleting conventional coarse aggregates in the Vindhyan regions of Northern India. The concrete samples were investigated by scanning electron microscopy and thermogravimetry. The microscopic study revealed the presence of increased void fractions in the concrete samples containing Quartz Sandstone aggregates. These void fractions were found to enhance the thermal resistance of concrete based on the reduced weight loss upon heating them and also assumed to improve insulation properties by hindering the heat transfer in the material. The efficient utilisation of these Quartz Sandstone wastes in concrete can reduce the substantial amount of landfill that is used for dumping them and also provide a valuable source of supplementary aggregate used in the production of cement concrete contributing to the overall sustainability.
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strength abrasion and permeability studies on cement concrete containing Quartz Sandstone coarse aggregates
Construction and Building Materials, 2016Co-Authors: Sanjeev Kumar, Ramesh Chandra Gupta, Sandeep ShrivastavaAbstract:Abstract Sandstones being a sedimentary type of rock are composed of sand-sized mineral grains, rock fragments and pieces of fossils which are held together by mineral cement. They differ from other igneous rocks in possessing a framework of grains that touches each other but not in continuous contact. Quartz being a mineral which is highly resistant to both physical and chemical weathering are also found in Sandstones. Being found in Sandstones, they can be used as partial replacement of aggregate in cement concrete without a substantial decrease in strength properties. In countries like India, Sandstone waste generation is very high and it is estimated that Rajasthan alone produces 900 million tonnes of Sandstone waste thus leading to a large dumping of these materials without any essential utilisation. To overcome this massive dumping of Sandstone wastes and to lessen the use of natural aggregates, a study was carried to find out the effective use of these Sandstone wastes in concrete. M30 grade of concrete was designed as per IS 10262: 2010, with water cement ratio of 0.4. However to find the scattering of strength plots, water cement ratios of 0.35 and 0.45 were also adopted for the study. Control mix consists of 0% Quartz Sandstone and substitution of coarse aggregates was done for 0–100%, in the multiples of 20%. Tests were done to determine the compressive strength, flexural strength, abrasion resistance, permeability and sorptivity in concrete samples. It was observed that the Quartz Sandstones might be utilised as a partial replacement of coarse aggregates up to 40% without considerable decrease in its preferred strength.
Ermanno Galli - One of the best experts on this subject based on the ideXlab platform.
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source and genesis of sulphate and phosphate sulphate minerals in a Quartz Sandstone cave environment
Sedimentology, 2014Co-Authors: Francesco Sauro, Nicola Tisato, Tomaso R R Bontognali, Stefano M. Bernasconi, Jo De Waele, Ermanno GalliAbstract:Gypsum (CaSO4·2H2O), alunite (KAl3(SO4)2(OH)6), and rare phosphate–sulphate sanjuanite Al2(PO4)(SO4)(OH) 9(H2O) and rossiantonite (Al3(PO4)(SO4) 2(OH)2(H2O)14) have recently been identified as secondary mineral deposits in different Quartz-Sandstone caves in the Gran Sabana region, Venezuela. Due to the extended time scale required for speleogenesis in the hard and barely soluble Quartz-Sandstone lithology, these caves are considered to be as old as 20 to 30 My. The study of these peculiar secondary mineral deposits potentially reveals important insights for understanding the interaction between deep, superficial and atmospheric processes over thousands to perhaps millions of years. In this study, chemical and petrographic analyses of potential host rock sources, sulphur and oxygen isotope ratios, and meteorological, hydrological and geographical data are used to investigate the origin of sulphates and phospho–sulphates. The results suggest that the deposition of sulphates in these caves is not linked to the Quartz-Sandstone host rock. Rather, these mineral deposits originate from an external atmospheric sulphate source, with potential contributions of marine non-sea salt sulphates, terrestrial dimethyl sulphide and microbially reduced H2S from the forests or peatbogs within the watershed. Air currents within the caves are the most plausible means of transport for aerosols, driving the accumulation of sulphates and other secondary minerals in specific locations. Moreover, the studied sulphate minerals often co-occur with silica speleothems of biological origin. Although this association would suggest a possible biogenic origin for the sulphates as well, direct evidence proving that microbes are involved in their formation is absent. Nonetheless, this study demonstrates that these Quartz-Sandstone caves accumulate and preserve allogenic sulphates, playing a yet unrecognized role in the sulphur cycle of tropical environments.
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Source and genesis of sulphate and phosphate–sulphate minerals in a Quartz-Sandstone cave environment
Sedimentology, 2014Co-Authors: Francesco Sauro, Nicola Tisato, Tomaso R R Bontognali, Stefano M. Bernasconi, Jo De Waele, Ermanno GalliAbstract:Gypsum (CaSO4·2H2O), alunite (KAl3(SO4)2(OH)6), and rare phosphate–sulphate sanjuanite Al2(PO4)(SO4)(OH) 9(H2O) and rossiantonite (Al3(PO4)(SO4) 2(OH)2(H2O)14) have recently been identified as secondary mineral deposits in different Quartz-Sandstone caves in the Gran Sabana region, Venezuela. Due to the extended time scale required for speleogenesis in the hard and barely soluble Quartz-Sandstone lithology, these caves are considered to be as old as 20 to 30 My. The study of these peculiar secondary mineral deposits potentially reveals important insights for understanding the interaction between deep, superficial and atmospheric processes over thousands to perhaps millions of years. In this study, chemical and petrographic analyses of potential host rock sources, sulphur and oxygen isotope ratios, and meteorological, hydrological and geographical data are used to investigate the origin of sulphates and phospho–sulphates. The results suggest that the deposition of sulphates in these caves is not linked to the Quartz-Sandstone host rock. Rather, these mineral deposits originate from an external atmospheric sulphate source, with potential contributions of marine non-sea salt sulphates, terrestrial dimethyl sulphide and microbially reduced H2S from the forests or peatbogs within the watershed. Air currents within the caves are the most plausible means of transport for aerosols, driving the accumulation of sulphates and other secondary minerals in specific locations. Moreover, the studied sulphate minerals often co-occur with silica speleothems of biological origin. Although this association would suggest a possible biogenic origin for the sulphates as well, direct evidence proving that microbes are involved in their formation is absent. Nonetheless, this study demonstrates that these Quartz-Sandstone caves accumulate and preserve allogenic sulphates, playing a yet unrecognized role in the sulphur cycle of tropical environments.
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rossiantonite al3 po4 so4 2 oh 2 h2o 10 4h2o a new hydrated aluminum phosphate sulfate mineral from chimanta massif venezuela description and crystal structure
American Mineralogist, 2013Co-Authors: Ermanno Galli, Maria Franca Brigatti, Daniele Malferrari, Francesco Sauro, Jo De WaeleAbstract:Rossiantonite, ideally Al3(PO4)(SO4)2(OH)2(H2O)10·4H2O, triclinic (space group P 1), a = 10.3410(5), b = 10.9600(5), c = 11.1446(5) A, α = 86.985(2), β = 65.727(2), γ = 75.064(2)°, V = 1110.5(1) A3, Z = 2, is a new mineral from the Akopan-Dal Cin cave system in the Chimanta massif (Guyana Shield, Venezuela). The mineral occurs as small (≤0.15 mm) and transparent crystals in a white to slightly pink fine-grained sand, filling spaces between boulders of weathered Quartz Sandstone. Associated phases are gypsum, sanjuanite, rare alunite, Quartz and micro-spherules of amorphous silica. Rossiantonite is colorless with a white streak and vitreous luster. The mineral is brittle with irregular to sub-conchoidal fracture and it shows a poorly developed cleavage. Rossiantonite is biaxial and not pleochroic, with mean refractive index of 1.504. The calculated density is 1.958 g/cm3. Electron microprobe analyses, with H2O measured by thermogravimetric analysis, provided the following empirical formula based on 28 O apfu: Al2.96Fe0.03P1.01S2H30.02O28. The five strongest lines in the X-ray powder diffraction pattern, expressed as d (A), I , ( hkl ) are: 4.647, 100, (210); 9.12, 56, (100); 4.006, 53, (220); 8.02, 40, (110); 7.12, 33, (011). The crystal structure, refined using 3550 unique reflections to R = 0.0292, is built of PO4 and Al O6 polyhedral rings, creating complex chains parallel b by sharing the OH-OH edge belonging to the Al(3) polyhedron. Three symmetrically independent Al sites can be identified, namely: Al(1), Al(2), and Al(3). Tetrahedral sites, occupied by P, share all their apexes with AlO6 octahedra. Unshared octahedral apexes are occupied by water molecules. Four additional water molecules are placed in between the previously identified chains. Two oxygen tetrahedra, occupied by S atoms, are connected along the chains by means of weak hydrogen bonding. The rossiantonite structure shows similarities with minerals belonging to the sanjuanite-destinezite group.