Silica Minerals Research Articles

Conceptual modelling on water-rock reaction and genesis of high pH fluids in a typical granitoid geothermal reservoir: A case from Indus-Tsangpo Suture Zone, India

Two novel thermal springs are investigated along ITSZ of north-west Himalayas in Demchok geothermal belt. The area consists of deep-seated faults in LGB; despite being situated in ITSZ, fluid chemistry of these low-temperature springs differs significantly, specifically in terms of low TDS (161–168 mg/l) and high alkalinity, with neighbouring springs in Puga and Chumathang (∼2100 mg/l). Thermal waters are mixed type (Na–Cl–HCO3–SO4) with elemental composition influenced through silicate rock weathering and partial carbonate dissolution. Variable temperature speciation (25 °C–200 °C) indicates that in reservoir fluid, Na+ precedes over other cations, while sulfate and carbonate complexes being prominent for Mg and Ca, respectively. Aquifer boiling modelling suggests calcite scaling and silica mineral equilibration in reservoir. Environmental stable isotopes (δ18O and δD) suggest high-altitude recharge from Jamlung La (6156 m), with altitude-effect of 0.43 ‰ isotopic depletion per 100 m elevation in altitude. As only silica minerals equilibrate with thermal waters, silica, and gas geothermometers give most conservative estimate of reservoir temperature (125°−135 °C). The steep topography enables extensive lateral flow of hot fluids in outflow zone, leading to high mixing and a high water-rock ratio, which contribute to lower TDS. Conceptual modelling reveals that geothermal system is a low-enthalpic hydrothermal system controlled by joints and permeable fractures, having deep fluid circulation of meteoric waters of ∼1275 m at sub-surface, with anomalous geothermal gradient and steam migration as reservoir heat sources. These fluids closely resemble springs of Guerrero state, Mexico, exhibiting similarities in low-TDS, high-pH, and high concentration of dissolved silica.

Episodic fluid charging and mixing triggers calcite-bearing agates in the Permian Emeishan Basalt, SW China

ABSTRACT Agate, a distinctive form of banded chalcedony, derives its characteristic appearance from the deposition of silica and the presence of impurities. A significant variety of agate-bearing calcite was identified in the Permian Emeishan Basalt located in the southwestern Sichuan Basin. This calcite-bearing agate provides valuable insights into the complex interplay and evolution of fluids and minerals. This study aims to provide a detailed description and analysis of the microscopic textural and geochemical characteristics of the agate, while elucidating the sequence of mineral deposition, fluid properties, and the genetic mechanism underlying its formation. The findings reveal that the agate primarily consists of lamellar calcite and banded chalcedony, exhibiting a variety of textures, thicknesses, and colours. Through the analysis of the transformation and precipitation of epidote and allanite, and the identification of four types of calcites and five micro-silica textures, it has been confirmed that the early stage of fluid in geodes involved the mixing of meteoric water with post-magmatic hydrothermal fluid. The middle and late stages involve the mixing of magmatic-hydrothermal fluid with organic-acid fluid. The charging of silica-rich hydrothermal fluids and the generation of hydrocarbons from organic matter cause fluctuations in SiO2 concentration, pH, and crystallization rates, contributing to the diversity of silica minerals, such as chalcedony and quartz. The interlayered growth observed between chalcedony and calcite is attributed to secondary metasomatism, which occurs after the dehydration and transformation of chalcedony due to increasing temperatures. Notably, the internal texture of the agate is somewhat influenced by pressure variations caused by the episodic charging of the fluid.

Synthesis and Characterization of Silicon Nanoparticles from Coal Fly Ash Using Ultrasonication as a Battery Anode

Fly ash, a byproduct of coal combustion, is rich in silica, alumina, and other minerals, making it a valuable resource for extracting high-purity silicon. The synthesis of silicon nanoparticles from coal fly ash involves several critical steps, including the extraction of silica (SiO2) via the sol-gel method, reduction of silica to silicon using the metallothermic method, and subsequent ultrasonication to achieve nanoscale particles. Studies have shown that fly ash can contain up to 49.21% silica, which can be further purified to 93.52% via chemical extraction methods such as acid leaching and alkali dissolution. The reduction of silica to silicon is carried out using the metallothermic method, which involves the use of magnesium-reducing agents to convert SiO2 to elemental silicon. This process produces silicon with a purity of about 61.3%, which can be further increased through ultrasonication. Ultrasonication is a technique that uses high-frequency sound waves to break particles into smaller sizes, resulting in more uniform and homogeneous nanoparticles. In this study, ultrasonication for 60 and 120 min reduced the average particle size of silicon from 208.94 nm to 58.87 nm and 20.13 nm, respectively, and increased the silicon content to 74.6% and 72.7%. X-ray diffraction (XRD) and distribution particle analyses confirmed the particle size reduction and homogeneity of silicon nanoparticles, indicating the effectiveness of ultrasonication in producing high-quality silicon nanoparticles. The synthesized silicon nanoparticles have significant potential applications, particularly as anode materials in lithium-ion batteries, due to their increased surface area and improved electrochemical properties. Furthermore, the use of fly ash as a raw material for the synthesis of silicon nanoparticles not only provides a cost-effective and environmentally friendly alternative to traditional silica sources but also helps in reducing the environmental impact of fly ash disposal. The integration of the methods and findings of this study underscores the feasibility and benefits of using coal fly ash for the sustainable production of silicon nanoparticles, which can be utilized in energy storage as anode materials in lithium-ion batteries.

Organic carbon cycling in the sediments of Prydz Bay, Eastern Antarctica: Implications for a high carbon sequestration potential

Understanding the dynamics of sedimentary organic carbon (SOC) in the productive continental marginal sea surrounding Antarctica is crucial for elucidating the effect of this sea on the global carbon cycle. We analyzed 31 surface sediment samples and eight sediment cores collected from Prydz Bay (PB) and the adjacent basin area. The element and stable isotope compositions, grain size compositions, and biogenic silica and lithogenic minerals of these samples were used to evaluate the spatial variations in the sources, transport mechanisms, and preservation patterns of SOC, with a particular focus on the efficiency of the biological carbon pump (BCP). Our findings reveal that the SOC originated from mixed marine/terrestrial sources. The δ13C values were higher in the Prydz Bay Gyre (PBG) region than in the open sea area. Biogenic matter-rich debris, associated with fine-grained particles (silt and clay), was concentrated in the PBG, while abiotic ice-rafted debris and coarse-grained particles were preferentially deposited in the bank and ice shelf front regions. Lithogenic matter predominated in the basin sediments. The annual accumulation rate of SOC in PB ranged from 1.6 to 6.2 g·m−2·yr−1 (mean 4.2 ± 1.9 g·m−2·yr−1), and the rates were higher in the PBG than in the ice shelf front region. Estimates based on our tentative box model suggest that the efficiency of the BCP, which refers to the proportion of surface-produced organic carbon successfully transferred to deep waters, is approximately 5.7 % in PB, surpassing the global average (∼0.8 %) and the efficiencies reported for other polar environments. Furthermore, our calculations indicate that the SOC preservation efficiency (the ratio of preserved to initially deposited organic carbon in sediments) in PB is approximately 79 % ± 20 %, underscoring the significant carbon sequestration potential within PB. The results of this study have important implications for the effects of sediment dynamics on the carbon cycle in the sea surrounding Antarctica.

Paleosol-induced early dolomitization with U[sbnd]Pb age constraints and its implications for fluid pathways in ancient sandstone aquifers

In hydrogeology, a key challenge involves identifying patterns within ancient formations to forecast the distribution of fluid pathways and barriers to permeability, as well as comprehending the palaeohydrological system and its changes over time. This study addresses two main research inquiries concerning fluid flow: firstly, the influence of dolomitization induced by paleosols on flow characteristics, and secondly, the implications for fluid flow pattern distribution in continental sedimentary units. The objectives are pursued through: (1) meticulous, high-resolution measurements of porosity and permeability coupled with well-log data from an outcrop and two boreholes; (2) investigation of petrographic features of diagenetic minerals and their ages using the UPb geochronology system; and (3) an integration of these methodologies to grasp rock properties and fluid flow at a broader scale. Findings suggest that early dolomitization in continental sequences significantly affects fluid flow properties across the basin. The development of paleosols triggered early dolomitization, supported by UPb geochronology evidence. Subsequent groundwater migration along hydraulic gradients, influenced by fluctuations in the local aquifer's water table, facilitated the vertical distribution of dolomitization. Dolomitization occurred in residual pores resulting from initial mineral alteration, early lithifying the sediment and preventing mechanical compaction, thus preserving porosity. During migration events, fluids moved vertically along local faults and horizontally through the dolomitized layers of the formation, which likely remained porous at the time, leading to substantial silica mineralization.

Pre-Jurassic weathering crust of the Kalinovoe hydrocarbon deposit, Tomsk region: composition and structure characteristics

Abstract. The study of pre-Jurassic deposits in the southwestern part of Western Siberia is highly relevant due to their potential of increasing hydrocarbon resources. These deposits are considered prospective targets for the discovery of hydrocarbon accumulations. Weathering crusts developed on the upper part of the Paleozoic rocks in the Tomsk region exhibit a complex composition and structure, reflecting the interplay of various factors, including primary sedimentary processes and later alteration processes, including fracture-controlled fluid flow and metasomatism. Aim. To establish the characteristics of the mineralogical composition and structure of the Paleozoic weathering crust formations developed at the Kalinovoe oil-gas-condensate field. Methods. Optical microscopy, X-ray diffraction, scanning electron microscopy. Results and conclusions. The composition and structure of the deposits at the boundary zone between the Paleozoic and Mesozoic successions have been studied in detail in the section of one of the wells at the Kalinovoe oil-gas-condensate field. The factual material is represented by core and thin sections of weathering crust deposits. The primary rock-forming minerals are silica minerals (quartz, chalcedony and opal) and clay minerals, with a lesser amount of carbonate minerals (siderite). Different lithological units were identified based on the content of minerals and bioclast (radiolarians and sponge spicules), indicating their formation under marine conditions. The protoliths of the altered rocks were carbonate-siliceous rocks, argillaceous limestones, and radiolarian cherts, which as a result of multiple stages of hydrothermal alteration and metasomatic processes were transformed into argillaceous-silicified rocks. In these rocks, with intense post-alteration overprinting, good reservoir quality porosity can develop. This porosity includes biogenic voids, microcavities, micropores, and open fractures.

One-step hybridization of silane hydrolysis and silica mineralization for enhanced superhydrophobic coating on cement-based materials

The complex and demanding marine environment poses significant challenges for concrete coatings. Despite the exceptional properties, superhydrophobic coatings have encountered limitations such as complex preparation processes and limited structural stability, thus impeding their widespread application. In this study, we employed molecular monomers to simultaneously conduct in-situ silica mineralization and silane hydrolysis reactions on mortar substrate. The mineralized product, nano-silica, effectively fills microcracks and pores, serving as an internal reinforcing agent. Simultaneously, the silica is utilized to construct a robust and dense micro-nano hybrid structure. The results in the preparation of a silica mineralized layer with exceptional mechanical strength on the surface. The in-situ hydrolysis of silane introduces a low surface energy for hydrophobic modification, leading to the formation of a stable superhydrophobic coating with a contact angle of 157°. Mineralized structure and hydrophobic surface offer both internal and external protective effects. This one-step approach promotes the complete hybridization of hydrophobic silane groups with the three-dimensional silica matrix. During the in-situ reaction process, the hydrolyzed silane molecules bond with the surface of silica microspheres, significantly enhancing the integrity and stability of the coating structure. Notably, even after multiple cycles of peeling and abrasion, the coating surface maintains its hydrophobic properties, further emphasizing its durability. The results demonstrate that this coating enhances both the structural and chemical performance of cement-based materials, paving the way for the expanded application and development of superhydrophobic coatings in the marine concrete industry.

Correlation and response of astronomical forcing in lacustrine deposits of the middle jurassic, sichuan basin, southwest China

The astronomical cycle characteristics of Mesozoic lacustrine fine-grained sedimentary rocks play a crucial role in understanding the formation environment of such sediments. The fine-grained sedimentary rocks of the Middle Jurassic Lianggaoshan Formation in the Sichuan Basin, China, constitute a significant lacustrine deposit. Previous research has primarily focused on its reservoir characteristics, with limited understanding of the relationship between lithofacies changes and astronomical cycles. To fill this knowledge void, we provide a continuous lacustrine core record of approximately 260 m from the XY-4 well, spanning the Lianggaoshan Formation in the Eastern Sichuan Basin. Initially, we categorized it into eight lithofacies types and established a lithologic ranking sequence based on this classification. Through time-series analysis, we identified the 405 Kyr long eccentricity cyc lecycle, 125 Kyr short eccentricity cycle, obliquity, and precession cycle. We emphasize the significance of the 125 Kyr short eccentricity cycle as the primary controlling factor during the deposition of the Lianggaoshan Formation. Subsequently, based on the 405 Kyr long eccentricity cycle, we established an age model for astronomical tuning, creating an astronomical age scale. The calculated sedimentation interval for the Lianggaoshan Formation ranges from 170.00 Ma to 172.74 Ma, spanning a total duration of 2.74 Ma. Meanwhile, the sedimentation interval for the Lower Liang 2 Submember is determined to be from 171.54 Ma to 172.52 Ma, lasting 0.98 Ma. Further comparison of TOC content and mineral composition with the orbital cycles reveals that TOC content and clay mineral content exhibit in-phase variations with the 125 Kyr short eccentricity. This characteristic contradicts the features of Cenozoic continental basins but aligns consistently with the characteristics of the Middle Triassic in North China. In contrast, silica minerals and carbonate minerals display anti-phase variations with the 125 Kyr short eccentricity. Different lithofacies demonstrate distinct responses to orbital cycles. Lithofacies characterized by higher organic matter content generally develop during the half-period with the maximum eccentricity. In contrast, lithofacies with lower organic matter content tend to occur during the half-cycle associated with the minimum eccentricity. Finally, based on the integrated analysis of lithological characteristics and astronomical cycles, we established two sedimentary modes: “Seasonally Pronounced Type” corresponding to the maximum eccentricity and “Seasonally Obscure Type” corresponding to the minimum eccentricity.

SYNTHESIS AND CHARACTERIZATION OF NANOSILICA (SiO2) VOLCANIC ROCK OF MOUNT BATUR IN BALI

This research was conducted to synthesize and characterize silica minerals (SiO2) from volcanic rocks in the active volcano in Bali, namely Mount Batur. The synthesis carried out on five different color variants of this rock sample is by the coprecipitation method which begins with the process of taking rock samples on Mount Batur, crushing the rock until it becomes powder with a size of 100 mesh, washing with distilled water and drying, immersing the rock powder in the solution. 2 M HCl for 12 hours, then the results of the soaking were reacted again with 7 M NaOH solution as a hydrolysis process to obtain pure SiO2 in the sample. In the form of sodium silicate precursor (Na2SiO3), the sample was titrated with a 2 M HCl solution to obtain silica gel which was then washed and dried until amorphous silica powder was produced. The results of the XRF analysis showed that the SiO2 mineral content in the sample after going through the synthesis process was 94.9% and the Si element was 89.9%. The XRD characterization results show that the phase formed from the sample has a quartz structure with the highest peak at an angle of 2θ = 23.07o, then decreases and levels out at an angle of 2θ = 32.94o which is characteristic of an amorphous structure and with a silica grain size of 8.47 nm – 8.65 nm.

PENGARUH SERBUK BATU PARAS BELAYU SEBAGAI SUBSTITUSI SEMEN TERHADAP KUAT TEKAN BETON

Cement is the most important building material in making concrete, cement is formed from the oxidation process or heating of limestone using coal at high temperatures. The heating process produces excess CO? which has a negative impact on the environment. So in this research, the researchers conducted research on the effect of sandstone powder (SBP) as a substitute for Portland cement (SPI) in concrete mixtures because sandstone contains silica and alumina minerals which are suitable for use. as pozzolan. The test object used in this study was a cube measuring (150 x 150 x 150) mm, with the ratio: (0% SBP: 100 SPI), (2.5% SBP: 97.5% SPI), (5%SBP: 95% SPI) and (10% SBP: 90% SPI) which were tested at 28 days of age. Concrete mix planning (mix design) is carried out based on SNI 7656-2012 with concrete design quality 20.75 MPa, classified as concrete quality for building structures. From the test results, it was found that the effect of sandstone powder as a cement substitute in the concrete mixture increased the compressive strength of the concrete at a percentage of 2.5% -5%, and at a percentage of 10% the compressive strength of the concrete decreased.

Petrography and Geochemistry of Limestone Upper Cretaceous Kometan Formation (Azmir Anticline): A Preliminary Assessment for Cement Production Suitability in the Kurdistan Region Northeast Iraq

A succession of slightly siliceous limestone of the Kometan Formation is studied geochemically and strati graphically. The studied area is located on the SW limb of the Azmir anticline at the northeastern of Sulaimaniyah city. The studied section is situated at longitudes 45°38'310"E and latitudes 35°36'129''N inside the Folded Zone, Kurdistan Region, northeastern Iraq. The exposed section is sampled for lab studies, and inspected by eyes and hand lenses in the field. In this study, petrographic and geochemical analyses of 17 limestone samples were carried out. This study aims to investigate the major oxides of the limestone samples, using the X-Ray Fluorescence (XRF), for preliminary assessment for possible cement production. A petrographic study was also carried out, in order. Depending on the petrographic study, three major microfacies were recognized: lime mudstone microfacies, lime wackestone microfacies, and lime packstone microfacies, which subdivided into four submicrofacies are planktonic foraminifera lime mudstone submicrofacies, planktonic foraminifera lime wackestone submicrofacies, and planktonic foraminifera lime packstone submicrofacies and heterohelix lime packstone submicrofacies. The geochemical analysis shows that a range of variations in constituents: LOI (35.90% to 42,72%), SiO2 (3.77% to 14.66%), CaO (42.59% to 49.95%), Al2O3 (0.44% to 2.22%), Fe2O3 (0.02% to 0.78%) and MgO (1.50% to 2.26%); K2O and Na2O are present in traces. The high CaO (49.95%) indicates that calcite is the primary carbonate mineral. Due to mineralogical considerations, CaO with LOI shows a positive correlation, whereas CaO with SiO2 shows a negative correlation. The low MgO contents in calcitic limestone and calcitic limestone with chert nodules recommend a lack of dolomitization process. The silica modulus and lime saturation factor from geochemical data indicated that the siliceous limestone samples from the Kometan Formation and Azmir Anticline can be used in the cement-making process provided they are processed for silica removal treatment to reduce its percentage to less than 8%, as required level, where the CaO can be automatically enriched. Depending on field observation, petrography, and geochemistry analysis, we conclude that the source of the chert or silica minerals is diagenetic processes and depositional environment origin.

Bismuthite and cassiterite-doped borosilicate glass systems for X-rays attenuation: Fabrication and characterisation

For the first time, X-ray shielding glass (XSG) was fabricated using rice husk (RH) silica, bismuth, and tin mineral ores. The objective was to promote waste valorisation and circular economy by minimising the use of analytical grade silicon and metal oxides in large-scale radiation shielding glass production. The physical, structural, and low-energy X-ray attenuation properties of the new bismuthite and cassiterites-doped glass were characterised using XRD, FTIR, and low-energy mobile X-ray shielding analyses. The X-ray shielding parameters linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half value layer (HVL), tenth value layer (TVL), and mean free path (MFP) were comparatively examined alongside commercial lead/barium XSG used in hospital radiology units. XRD results showed that glasses with 0, 5 and 15 wt% dopants contain nanocrytallites measuring 19.43, 38.85 and 42.44 nm, respectively, with peaks in the 2Θ (28°) vicinity. FTIR revealed structural modifications that demonstrate the network modulation capabilities of cassiterite-sourced Sn ions. At 70 kVp tube voltage, the MAC of the 20 wt% dopant glass compares favourably with commercial Pb/Ba glass, while the 25 wt% variant has lower values than commercial Pb/Ba glass at 80 kVp tube voltage. The HVL and MFP of 25 wt% dopant glass compared favourably with commercial glass at 60 kVp X-ray tube voltage, suggesting the new glasses with x = 15, 20, 25 wt% dopants are competitive candidates for viewing window applications in low energy X-ray radiology units. Future studies will investigate the radiation attenuation efficiency of the new glass systems using point gamma sources.

Development a novel empirical approach to control overbreak, surface quality and slope angle of benches following blasting

Overbreak, slope angle and quality of a bench behind the boundary of excavation as attractive subjects for mining and civil engineers are the most crucial consequences of the post-blast. But the breakage mechanism of blasting has not originally been well clarified how a desirable slope angle and quality of a bench can be obtained by common drilling and blasting operations and what parameters can affect such blasting consequences? The breakage mechanism and influence of the blasthole parameters such as hole diameters, explosive weight per hole, burden, spacing, stemming, bench height, powder factor and blastability index on the depth of the overbreak zone (L<sub>OZ</sub>), the difference between hole and bench slope angles (α°-β°) and the width of damaged zone (L<sub>DZ</sub>) in fifteen zones of Sun gun open pit copper mine, Golgohar open pit iron ore mine, Khoy limestone, Rashakan limestone, Bonab silica mine and Evoghli gypsum mine were investigated. New multivariable nonlinear relations between each of L<sub>OZ</sub>, (α°-β°) and L<sub>DZ</sub> with the combination of Φ<sub>h</sub>, Q, B, S, S<sub>t</sub> and K were developed. The new achievements in this study can be new guides to obtain the desirable bench slope angle and bench faces.

The Effect of Using Sustainable Copper Fiber on Some Mechanical Properties of High Strength Green Concrete

Finding an alternative to materials that pollute during manufacturing, most notably cement, is vital to executing the idea of sustainability in the building sector. It was vital to develop concrete that assists in the reduction of CO2 (Carbon dioxide) in the atmosphere because industrial wastes contain calcium, silica, and aluminous minerals, such as silica fume, that are employed in the production of high-strength concrete and have parameters that are identical to those of regular concrete. As a substitute for Portland cement, lime cement was utilized, and 15% of the cement's weight was substituted with silica fume. Environmentally friendly fibers (Copper Fiber) created from old electrical and electronic equipment were also employed. The purpose of the study is to produce High Strength Green Fiber Concrete (HSGFC) by incorporating silica fume as a replacement and study the effect of adding fiber on some mechanical attributes. The task needed the creation of a high strength concrete mixture of cement with a compressive strength of 65 MPa in accordance with ACI 211.4R, as well as the development of numerous experimental mixtures that relied on the findings of earlier researchers. The mechanical properties (compressive strength, flexural strength and split tensile strength) of samples are tested at 7, 28 and 60 days with standard curing. The results show that adding sustainable fiber to concrete mix enhances the mechanical properties such as compressive strength by 16% at 28 days, flexural strength by 35% and spilt tensile strength by 44% at 28 days Compared with concrete mix with no fiber. Also, the outcomes showed that it is feasible to develop High Strength Concrete (HSC) using sustainable copper fiber possessing exceptional stress resistance, tensile strength, and flexural strength.

Morphology, Crystal Structure and Thermal Properties of Nano-Sized Amorphous Colemanite Synthesis

It is important to utilize the raw colemanite (RC) mineral, which has abundant reserves in the world, and to reduce its particles to smaller sizes for nanotechnology. However, not only the particle size of the produced colemanite powder but also its other properties need to be elucidated. By using the Taguchi design, the RC mineral was ground in a high-energy ball mill. From signal-to-noise (S/N) ratio, the smallest average particle size was found to be 3.10 µm for the experiment E04/nano-sized amorphous colemanite (NAC) powder. The characteristics of as-received RC mineral and synthesized NAC material were investigated using laser particle size analyzer, optical microscopes, SEM–EDS, XRD, TEM, HRTEM, and TGA–DTA devices. It was found that the NAC powder was not homogeneous, a small peak within the 300–20 nm range appeared, and d90, d50, d10, and dmin values were, respectively, 14.6 µm, 3.08 µm, 232 nm, and 26 nm. In the XRD analysis, the pure colemanite, calcite, and silica minerals were determined. The crystal structure of the NAC powder almost turned amorphous, and the crystallite size of (031) peak was reduced to 7.3 nm. It was deduced that the average particle size was 8.29 nm (R2 = 0.86), and the d-spacing value was 0.307 nm. This significant finding was attributed to the mobility of balls and moreover it was interpreted with an equation. An unknown transition in TGA–DTA was referred to the calcite mineral. Finally, it is believed that the synthesized NAC material will be beneficial to engineering studies as a natural/mineral additive.

Optimizing the development and field application of calcium stabilizing agents for preventing calcium leaching in tunnels

As a hidden engineering structure, tunnels are inevitably affected by the long-term erosion of groundwater, resulting in the phenomenon of calcium leaching in shotcrete. The effective components of the initial tunnel support are dissolved by groundwater, with a portion remaining in the tunnel drainage system and the rest discharged from the tunnel. This phenomenon can further accelerate the deterioration of the lining and cause blockages in the drainage system, posing new challenges to environmental protection and structural safety. To mitigate the problem of calcium leaching in tunnel shotcrete, new building materials, termed Calcium Stabilizing Agents (CSAs), were fabricated using industrial solid wasters such as silica fume, mineral powder, silicone zirconium, and metakaolin. An orthogonal experiment was implemented to investigate the influence of CSAs on the calcium ion (Ca2+) leaching concentration; the sensitivity analysis was conducted to identify the impact of each ingredient of CSAs on the calcium ion leaching concentration; and microscopic methods such as XRD, SEM, and TG were used to analyze the mechanism of the CSAs on anti-calcium leaching ability of mortar. The results showed that the addition of the CSAs can effectively improve the anti-calcium leaching ability of mortar. For the optimal dosage of the CSAs mortar, the calcium ion concentration of the 28-day CSAs mortar was reduced by 31.55 %, and the compressive strength and flexural strength were enhanced 31.09 % and 37.27 %, respectively. From the sensitivity analysis of calcium ion concentration, compressive strength, and flexural strength of CSAs mortar at 1 day, 7 days, and 28 days, silica fume and zirconium silicone show the greatest influence on the performance of mortar. Consequently, they are deemed as the core components of CSAs. The microscopic analysis showed that the internal cementitious structure of the cement stone grew denser after CSA was added. It also contained long-chain crystalline structures that effectively fill capillary pores to resist erosion. Finally, the CSAs product was applied to a tunnel under construction on site, and the results showed that the shotcrete mixed with CSAs had a good anti-calcium leaching effect and significantly improved compressive strength. The findings of this study can provide a new avenue for preventing and controling the tunnel crystallization diseases.

Hydrogen partitioning between stishovite and hydrous phase δ: implications for water cycle and distribution in the lower mantle

Water is transported into the deep mantle by subducting slabs, playing important roles in mantle dynamics and evolution. An aluminous hydrous mineral, phase δ with a main component of AlOOH, has been considered an important water carrier in the lower mantle. Recent studies reported that SiO2 stishovite can accommodate weight percent levels of water, indicating another important water carrier in the lower mantle. However, which mineral can mainly carry water is not clear yet. Recent hydrous phase relation studies reported that stishovite is depleted in alumina when coexisting with hydrous phase δ, in which water content of stishovite was not investigated. In this study, we investigated hydrogen partitioning between stishovite and hydrous phase δ at 24–28 GPa and 1000–1200 °C by means of Kawai-type multi-anvil press in combination with Fourier-transform infrared spectroscopy at ambient conditions on recovered samples. Fourier-transform infrared spectra of recovered stishovites showed that water contents of stishovite coexisting with hydrous phase δ were limited to up to ~ 500 ppm. This indicates that coexisting hydrous phase δ causes not only depletion in alumina but also in hydrogen in stishovite and therefore mainly transports water in a cold subducting slab. Once hydrous phase δ becomes thermally unstable, alumina and water contents in silica minerals are increased by the chemical reaction between SiO2 and AlOOH, and aluminous silica minerals such as stishovite and CaCl2-type phase will be a main water carrier in the lower mantle. Presence of small-scale seismic scatterers observed around 1900 km depth, which was considered to be caused by a transition from almost pure SiO2 stishovite to CaCl2-type phase, might also be able to be explained by the phase transition of stishovite coexisting with hydrous phase δ.

PROCESS FOR RECOVERING SILICA FROM LITHOMARG CLAY: VALUE ADDITION OF UNEXPLOITEDMINING REJECT

Physico-chemical treatment was adopted for processing alumino-siliceous lithomarg clay known as saprolite. The study explained the potential of utilizing saprolite clay as fast resource for recovering silica mineral phases for value added utilization of unused mining reject. The conversion of saprolite to silica enriched low iron precursor was achieved by chemical activation with 1:1 v/v aqueous hydrochloric acid. Recovery of nano-silicate was achieved from the low iron precursor by dissolution in aqueous sodium hydroxide followed by precipitation in acid medium and centrifugation. Physical characterization of silicate nano particle was accomplished by scanning electron microscopy (SEM) and the range of impurities was determined by inductively coupled plasma (ICP) analysis.

To Study the Partial Replacement of Cement with Sugarcane Bagasse and Wood Ash with Addition of Aramid Fiber

Abstract: Concrete is widely considered for its strength to withstand heavy loads and that‟s why this matrix is used for construction purposes. The growth in population has placed an enormous need for more and more infrastructure and it keeps growing. The outcome of this demand is the increase in production of cement. Massive amount of waste materials and byproducts are produced by manufacturing enterprises such as silica fumes, wood ash, and mineral slag and so on. As a result, waste management has become a huge problem for our environment. There are several minerals in wood ash, which can be extracted for further use. A big ingradient calcium carbonate, which is 25% or even 45% (depending on feedstock and burining condition). Less than 10 percent is potash and less than 1 percent is phosphate; there are some elements of iron, manganese, zinc, copper and some metal parts. These numbers however, vary as combustion temperature is an important element for the determination of wood ash. Many of these are in the form of oxides, mainly. If we mix the ashes to water the insoluble silica and calcium carbonate will settle to bottom and sodim salt and soluble potassium will dissolve. Sugarcane is commonly used to produce sugar and ethanol. After sugar juice is extracted from sugarcane, sugarcane bagasse is produced, which is about 50% of the sugarcane level. Bagasse is widely used as a fuel in combining steam production and power generation. In this process, sugarcane ash (SCBA) remains the last waste in the sugar production chain.. However, SCBA is generally disposed of in landfills in India The experimental investigations are carried out for compressive strength, split and flexural strength for curing period of 7, 14 and 28 days. The experimental results show that the for a combined replacement percentage of 8&8%, which includes 8% SCBA and 8% WOOD ASH with addition of aramid fiber 1.2% the values of compressive strength, flexural strength and split tensile strength were higher when compared to other replacement percentages The result shows that concrete workability is fine and within limits after replacing cement with SCBA, WOOD ASH with addition of aramid fiber. However, workability gets reduced at higher replacement of materials. The strength parameters such as compressive strength, flexural strength, and split tensile strength also increase and show an optimum value at 8&8% cement replacement and 1.2% Addition of aramid fibers respectively.

Coal facies of the Middle Permian Baruunnaran deposit, South Mongolia

The Baruunnaran coal deposit is located in the northeastern part of the South Gobi Basin, southern Mongolia, and hosted in the middle Permian Tavantolgoi Formation. In this paper we present indices of coal facies determined from 34 coal samples obtained from three seams in the lower and upper part of the formation (III, IXG and X), by studying their organic petrography and the geochemistry of the coal ash. The results of coal petrography revealed that seams III, IXG and X are composed of 46.9-80.9 vol.% vitrinite, 11.6-47.5 vol.% inertinite and 1.2-18.2 vol.% liptinite. In samples from seams III and X the average content of mineral matter is low at 11 and 13.4 vol.%, respectively, and 6.3 vol.% in seam IXG, and consists of clay, silica, pyrite, carbonate, and other minerals. The inorganic content mostly occurs as fillings of cell cavities, cracks, and fissures of vitrinite and inertinite macerals. The vitrinite random reflectance values range from 0.81-1.07%. The Gelification Index and Tissue Preservation Index suggest the peats accumulated in wet forest swamp environments with high tree density. The majority of the seams accumulated in mildly oxic to anoxic conditions with good tissue preservation. The peat mire water ranged from weakly to strongly acidic. Further, it was determined by Al2O3/TiO2 ratios that the clastic sediments were probably sourced from volcanic basement characterized by intermediate felsic composition.