The molybdenum-nickel deposits in Shuidong District of Nayong County （Guizhou Province, Southwest China） are found mainly in black shale series of Lower Cambrian Niutitang Formation, which is another Mo-Ni-rich regi...The molybdenum-nickel deposits in Shuidong District of Nayong County （Guizhou Province, Southwest China） are found mainly in black shale series of Lower Cambrian Niutitang Formation, which is another Mo-Ni-rich region besides Zunyi District （Guizhou province）. Our systematic study on the Mo-Ni deposits in Tangjiaba of Nayong reveals that layered coarse-grained limestones, spherical beaded limestones concretions are hosted at the lower seam of the Mo-Ni deposits. Its strong negative carbon isotope anomaly （the carbon isotope value of the coarse-grained limestones varies from -2.148‰ to 8.223‰） is similar to that in the modern submarine black smoker chimney. The carbon in the coarse-grained limestones from black rock series of Nayong County might be deep source inorganic carbon. The seams, coarse-grained limestones, ore-bearing coarse-grained limestones and the roof and floor of the deposits are characterized by co-variation on the trace element spider diagram, showing good homology. The extraordinary enrichment of Ag, As and Sb resembles hydrothermal sedimentation. Pro-Earth＇s core elements Se is strongly enriched in Ni-Mo ore-bearing coarse-grained limestones. The ore-bearing rock series has an extremely low Th/U value （0.012-0.19）; in the logU-logTh Cartesian Coordinates, the samples of the roof and floor of the deposits and ore-bearing coarse-grained limestones are found in the East Pacific tise; and the samples of coarse-grained limestones are found between the paleo-hydrothermal dedimentary area and the East Pacific tise. The chondrite-normalized rare earth element patterns of the Ni-Mo deposits show LREE enrichment, Ce negative anomaly, and Eu negative anomaly （which is supposed to be influenced by the deep magmatic processes in an extensional environment） resembles the rare earth element distribution patterns of the fluid and its sediments in modern submarine hydrothermal system. It proves that coarse-grained limestones is characterized by typical hydrothermal limestones, being closely related with the genesis of Mo-Ni deposits in Nayong County, which provides new evidence for hydrothermal sedimentary genesis of Mo-Ni deposit and negative carbon anomaly in the basal Cambrian on a global scale.展开更多
This study examines the rare earth elements and yttrium(REY)concentrations of twenty-five samples from the reef outcrop exposed along the Lianglitage Mountain in the Ordovician,Tarim Basin in China.The concentration a...This study examines the rare earth elements and yttrium(REY)concentrations of twenty-five samples from the reef outcrop exposed along the Lianglitage Mountain in the Ordovician,Tarim Basin in China.The concentration analysis provides constraints on the paleoenvironment during reef deposition.Based on the detailed sedimentology and petrographic work,we divide the reef facies into four sub-facies:the base facies,reef-core facies,reef-flank facies,and sealing facies.The geochemical data(such as major and trace elements,carbon and oxygen isotopes,and REYs)are further used to study the coeval seawater characteristics as well as potential diagenesis overprints.The result indicated that the diagenesis has little effect on the REY patterns of the reefal limestones.The REY concentrations of the reefal limestones are overall low(ranging from 3.69 to 19.60 ppm,arithmetic mean=10.22 ppm,SD=5.4).The PAAS-normalized REY patterns are consistently flat compared to the typical well-oxidized,shallow marine water patterns.However,the light REE(LREE)depletions,positive La anomalies,negative Ce anomalies and positive Y anomalies,suggest that these reefal limestones are likely an indicative of contemporaneous seawater REY signals.The seawater-like Y/Ho ratios(average at 37.51)further support that REY signals in these limestones are likely a reflection of seawater with little diagenetic modifications.The low Y/Ho ratios presented only in the reef-flank facies and sealing facies are likely a suggestion of detrital contamination.Hence,this study confirms that REY patterns of the limestones at the base facies and reef-core facies can record ancient seawater information,and reefs can be used as a potential geochemical proxy for paleoenvironment studies throughout the Earth’s history.展开更多
The main aim of this work is to study the possibility of using different Emirati limestones for the production of quicklime. Representative limestone samples have been collected to represent the Triassic, Jurassic, Cr...The main aim of this work is to study the possibility of using different Emirati limestones for the production of quicklime. Representative limestone samples have been collected to represent the Triassic, Jurassic, Cretaceous, Eocene and Oligocene ages. The limestone samples have been characterized for their microstructure, mineral and chemical composition, physico-mechanical characteristics, thermal behavior using polarizing and scanning microscopes together with X-ray micro-tomography, XRD-IR, XRF, Archimedes and Mercury intrusion methods and DTA-TGA, respectively. Post characterization, the samples were fired in electrical muffle furnace for calcination under the firing conditions (800℃ to 1100℃) for (0.25 – 2 h). Then the lime grains have been characterized for their hydration rate, free lime content, pore-distribution and microfabric.展开更多
This study presents an analysis of magnetic susceptibility and natural gamma radioactivity as indirect indicators of impurities in Cretaceous limestones of the Sabinas basin, as well as of the possible relation of the...This study presents an analysis of magnetic susceptibility and natural gamma radioactivity as indirect indicators of impurities in Cretaceous limestones of the Sabinas basin, as well as of the possible relation of these physical properties with the changes in the sedimentation environment. Both of these physical properties indicate changes in the degree of impurities and the mineralogical composition of this rock, principally in its organic matter and detritus content. Considering that the sedimentation environment determines the impurities in these rocks, possible environmental conditions at different levels of the Cretaceous were suggested using the magnetic susceptibility, total gamma radiation and potassium values, as well as the uranium and thorium concentration in the limestones. The analyses suggest variations in the depth of water table of the basin, which are mainly related to transgressions and marine regressions.展开更多
Massive limestones were used in construction of ancient Egyptian tombs, temples, obelisks and other sculptures. These stones are always exposed to physico-mechanical deterioration and destructive forces, leading to pa...Massive limestones were used in construction of ancient Egyptian tombs, temples, obelisks and other sculptures. These stones are always exposed to physico-mechanical deterioration and destructive forces, leading to partial or total collapse. The task of reassembling this type of artifacts represents a big challenge for the conservators. Recently, the researchers are turning to new technologies to improve the properties of traditional adhesive materials and techniques used in re-assembly of broken massive stones. The epoxy resins are used extensively in stone conservation and re-assembly of broken stones because of their outstanding mechanical properties. The adding of nanoparticles to polymeric adhesives at low percentages may lead to substantial improvements of their mechanical performances in structural joints and massive objects. The aim of this study is to evaluate the effectiveness of montmorillonite clay, calcium carbonate, and silicon dioxide nanoparticles for enhancing the performances of epoxy adhesives used in re-assembly of archaeological massive limestones. Scanning electron microscopy (SEM) was employed in order to investigate the morphology of the prepared nanocomposites, and the distribution of nanoparticles inside the composites. Artificial aging, tensile, compressive, and elongation strength tests were used to evaluate the efficiency of epoxy-nanocomposites. The results showed that the epoxy-clay nanocomposites exhibited superior tensile, compressive, and elongation strength, in addition to improving the mechanical properties of stone joints.展开更多
Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conv...Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conventional rocks both in terms of rock structure and mechanical properties. In this study, mesoscale uniaxial compression experiments with five different loading directions were conducted on two kinds of reef limestones from the Maldives Islands and the South China Sea, respectively. The real-time high-resolution videos and images of failure processes were recorded simultaneously to investigate the fracture evolution and fracture surface roughness of reef limestones. It demonstrated that the reef limestones belonged to extremely soft to soft rocks, and their uniaxial compressive strength (UCS) values fluctuated with high discreteness. The mesoscale mechanical properties of reef limestones were highly anisotropic and mainly controlled by pore structure. The occurrence of dissolution pores in reef limestone tended to intensify mechanical anisotropy. With the integration of the fracture initiation and propagation features of reef limestones, it is supposed that the intrinsic mechanism of anisotropy was probably attributed to the differences in coral growth direction and dissolution. Furthermore, the quantified fracture surface roughness was revealed to have a good consistency with density and UCS for the reef limestones from the South China Sea. The findings are helpful for providing theoretical and experimental references for engineering construction in coral reef areas.展开更多
Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Ea...Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Eastern Pontides).They are well correlated with Aptian bitumen limestone in the other Tethys Reams.They are proposed as episodes of increased organic matter.However,background factors controlling organic matter enrichment are poorly known.In this study,we present new inorganic geochemistry,including trace elements,rare earth elements(REE),redox-sensitive elements(RSE),stable-isotopes(δ~(18)O andδ~(13)C),and total organic carbon(TOC).We integrated new geochemical data with existing stratigraphy,paleontology,and organic chemistry data to provide new insight into the depositional environment and paleoclimate conditions during Aptian.The lacustrine bitumen limestone(LBL)samples have variedδ~(13)C(ave.-1.45‰)andδ~(18)O(ave.-4.50‰).They possess distinct REE patterns,with an average of REE(ave.14.45 ppm)and Y/Ho(ave.35)ratios.In addition,they have variable Nd/YbN(0.28-0.81;ave.0.56)and Ce/Ce*(0.68-0.97;ave.0.86),and relatively high Eu^(*)/Eu(1.23-1.53;ave.1.35).They display seawater signatures with reduced oxygen conditions.The enrichment in RSE(Mo,Cu,Ni,and Zn)and the low Mo/TOC(0.70-3.69;ave.2.41)support a certain degree of water restriction.The high Sr/Ba,Sr/Cu,Ga/Rb,and K/Al records of the LBL facies suggest hot house climatic conditions.The sedimentary environment was probably an isolated basin that is transformed from the marine basin.In addition to depositional conditions,the regional parameters such as the climate,increased run-off period,nutrient levels,alkalinity level,and dominant carbonate producers favored the enrichment in organic matter of LBL facies.Thus,extreme greenhouse palaeoclimate conditions have an important role in organic matter enrichment in the isolated basin.Our results are conformable with the published data from marine,semi-restricted basin,and lacustrine settings in the different parts of the Tethys margin.Thus,this approach provides the first insight into the Aptian greenhouse paleo-climate conditions of the Eastern Black Sea Region,NE Turkey.展开更多
The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- mari...The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction （chemical and mechanical）, internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these lime- stones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar car- bonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/ Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system.展开更多
Carbon and oxygen XRF spectra were studied using a WDXRF(WD X-ray fluorescence)spectrometer S8 TIGER(Bruker AXS,Germany).XRF spectra were obtained from the samples of the calcareous spar(CaCO3)(pure calcium carbonate)...Carbon and oxygen XRF spectra were studied using a WDXRF(WD X-ray fluorescence)spectrometer S8 TIGER(Bruker AXS,Germany).XRF spectra were obtained from the samples of the calcareous spar(CaCO3)(pure calcium carbonate),the limestones,the graphite,the microcrystalline cellulose,various organic compounds and prepared mixtures on the basis of the calcareous spar with addition of the graphite and the microcrystalline cellulose.The studied samples of the limestones are characterized by high concentrations of calcite(98.5-99%).Main objective of this investigation is to develop WDXRF technique for the determination of C(total)and O(total).Optimal instrumental measuring conditions were selected experimentally for quantitative determination of C(total)and O(total).The calculated values of the ILD(instrumental limit of the detection)vary from 0.0215%for C(total)to 0.0331%for O(total),respectively.The obtained values of the LDM(limit of determination of the XRF method)do not exceed 0.08%for C(total)and O(total).The RSDs(relative standard deviations)values do not exceed 1.0%in all cases.展开更多
Limestones of different facies in the Senegal basin are most commonly used as aggregates, regardless of their petrographic properties. These differences may influence their behaviour. The aim of this paper is to study...Limestones of different facies in the Senegal basin are most commonly used as aggregates, regardless of their petrographic properties. These differences may influence their behaviour. The aim of this paper is to study the stratigraphy and characterise the limestones of the Bandia and Popenguine quarries. Sampling and geochemical and geotechnical characterisation were carried out on these limestones. The results show the presence of several very different facies in the Paleocene formation. The geochemical study shows that the Bandia limestones (Bd2) have the highest CaCO<sub>3</sub> percentages (98.54%) and the highest SiO<sub>2</sub> percentages were recorded in the Popenguine limestones (Pop2). The study also gives MDE values of 22.38 and LA of 22, which are acceptable for use in road construction. It is important to carry out a complete study in order to select the right materials for optimal use.展开更多
Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an...Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.展开更多
Among the rolling hills and vineyards of the Tuscan countryside lies one of the most impressive tourist attractions not only in Italy,but in the entire world-a cascade(小瀑布)of white limestone pools overflowing with ...Among the rolling hills and vineyards of the Tuscan countryside lies one of the most impressive tourist attractions not only in Italy,but in the entire world-a cascade(小瀑布)of white limestone pools overflowing with warm turquoise(绿松石色)water known as Cascate del Mulino.展开更多
The production processes for Si and FeSi have traditionally been considered slag-free.However,recent excavations have revealed significant accumulation of CaO–SiO_(2)–Al_(2)O_(3)slag within the furnaces.This accumul...The production processes for Si and FeSi have traditionally been considered slag-free.However,recent excavations have revealed significant accumulation of CaO–SiO_(2)–Al_(2)O_(3)slag within the furnaces.This accumulation can obstruct the flow of materials and gases,resulting in lower metal yield and higher energy consumption.The main objective of the current work is to enhance our understanding of slag formation during Si and FeSi production.We investigate slag formation through the dissolution of limestone and iron oxide in quartz and condensate,focusing on the reactions between these materials at a gram scale.Our findings indicate that most slag reaches equilibrium relatively quickly at temperatures starting from 1673 K.Notably,slag formation starts at lower temperature when the iron source is present (1573 K) compared to when only CaO is involved (1673 K).The minor elements tend to accumulate at quartz grain boundaries prior to slag formation.Furthermore,the slag produced from condensate contains less SiO_(2)than that generated from quartz with limestone.The type of quartz source and SiO_(2)phase appears to have little influence on slag formation.Good wettability is a significant factor in reaction between quartz and slag.FactSage calculations indicates that the viscosity of the slag ranges from 0.02 to 14.4 Pa·s under furnace conditions,comparable to the viscosity of honey or motor oil at room temperature.展开更多
In view of the increased focus on“green”and sustainable development and compliance with the national strategy for“carbon peak and carbon neutrality,”this study investigated the effect of replacing cement(0-20%)wit...In view of the increased focus on“green”and sustainable development and compliance with the national strategy for“carbon peak and carbon neutrality,”this study investigated the effect of replacing cement(0-20%)with limestone powder(stone powder)as a mineral admixture on the micro,meso,and macro properties of mortar.First,the applicability of stone powder was examined based on the physical filling and heat of hydration of stone powder-cement.Second,micro-meso testing methods,such as X-ray diffraction,scanning electron microscopy,thermogravimetry-differential scanning calorimetry,and nuclear magnetic resonance,were utilized to reveal the influencing mechanisms of stone powder on the microstructure of the mortar.Furthermore,the effect of stone powder on the compressive strength and gas permeability of the mortar was analyzed.Additionally,the time-dependent variations in the gas permeability and its functional relationship with the mechanical properties were determined.Finally,the correlation between the compressive strength and gas permeability with respect to the pore size of stone powder-doped mortar was established via gray-correlation analysis.The results show that an appropriate amount of stone powder(5%)can effectively improve the particle gradation,decelerate the release of the heat of hydration,increase the amount of hydration products,and improve the pore structure,thereby increasing the compressive strength and reducing the gas permeability coefficient.The gas permeability of stone powder-doped mortar was found to exhibit good time-dependent characteristics as well as a quadratic linear correlation with the compressive strength.The gray-correlation analysis results indicate that air pores exhibit the highest influence on the compressive strength and that the gas permeability coefficient is most significantly affected by large pores.展开更多
Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological s...Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.展开更多
In recent years,drilling data from wells Pengshen 10,Heshen 9,Tongshen 17 and Zhengyang 1 in the Sichuan Basin have confirmed the presence of a set of porous reef-beach limestone reservoirs in the Upper Permian Changx...In recent years,drilling data from wells Pengshen 10,Heshen 9,Tongshen 17 and Zhengyang 1 in the Sichuan Basin have confirmed the presence of a set of porous reef-beach limestone reservoirs in the Upper Permian Changxing Formation,which breaks the traditional view that deep carbonate oil and gas are only distributed in porous dolomite reservoirs and karst fracture-cavity limestone reservoirs.Through core and thin section observations,geochemical analysis,and well-seismic based reservoir identification and tracking,the study on formation mechanism of pores in deep reef-beach limestone reservoirs is carried out,this study provides insights in four aspects.(1)Porous reef-beach limestone reservoirs are developed in the Changxing Formation in deep-buried layers.The reservoir space is composed of intergranular pores,framework pores,intra-fossil pores,moldic pores and dissolution pores,which are formed in depositional and epigenetic environments.(2)The intermittently distributed porous reef-beach complexes are surrounded by relatively dense micrite limestone,which leads to the formation of local abnormal high-pressure inside the reef-beach complexes with the temperature increased.(3)The floor of the Changxing Formation reservoir is composed with interbedded tight mudstone and limestone of the Upper Permian Wujiaping Formation,and the roof is the tight micrite limestone interbedded with mudstone of the first member of Lower Triassic Feixianguan Formation.Under the clamping of dense roof and floor,the abnormal high-pressure in the Changxing Formation is formed.Abnormal high-pressure(overpressured compartment)is the key to maintain the pores formed in the depositional and epigenetic environments in deep-buried layers.(4)Based on the identification of roof,floor and reef-beach complexes,the favorable reef-beach limestone reservoir distribution area of 10.3×10^(4) km^(2) is predicted by well-seismic integration.These insights lay the theoretical foundation for the development of deep porous limestone reservoirs,expand the new field of exploration of deep-buried limestone reservoirs in the Sichuan Basin.展开更多
Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe...Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts.However,limited studies(mostly based on empirical field observation and small-scale laboratory tests)have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems.This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale(specimens with edge length of 0.5 m)for incorporation of actual support elements,with consideration of different w/h ratios.Both unsupported and supported(grouted rebar rockbolt and wire mesh)tests were conducted,and the surface deformations of the specimens were monitored using three-dimensional(3D)digital image correlation(DIC).Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution,load mobilization,and localized deformation at different w/h ratios.Both axial and bending strains were observed in the rockbolts,which became more prominent in the post-peak region of the stress-strain curve.展开更多
High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic bind...High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic binder,demonstrates significant potential for improving the engineering characteristics of such soils.Nevertheless,the impact of LC3 on the physico-mechanical characteristics of treated soil under a cyclic wet-dry environment remains unclear.This study for the first time investigates LC3's impact on the long-term durability of treated high-plastic clays through comprehensive macro-micro testing including physical,mechanical,mineralogical,and microstructural investigations with an emphasis on wet-dry cycles.The results revealed that LC3 treatment exhibits significant resistance to wet-dry cycles by completely mitigating the swelling potential,and a considerable reduction in plasticity resulting in enhanced workability.The compressibility and shear strength parameters have been significantly improved to several orders of magnitude.However,after six wet-dry cycles,a slight to modest reduction is observed,but overall durability remains superior to untreated soil.Cohesive and structural bonding ratios quantitatively assessed the impact of wet-dry cycles emphasizing the advantage of LC3 treatment.According to mineralogical and microstructural evaluation,the mechanism behind the adverse effects of wet-dry cycles on the compressibility and strength behavior of LC3-treated soil is mainly attributed to:(1)weakening of CSH/C(A)SH and ettringite(AFt)phases by exhibiting lower peak intensities;and(2)larger pore spaces due to repeated wet-dry cycles.These findings highlight LC3's performance in enhancing the long-term behavior and resilience of treated soils in real-world scenarios,providing durable solutions for infrastructure challenges.展开更多
Recently,we developed an innovative CO_(2)capture and storage method based on simple chemical reactions using NaOH and CaCl_(2).In this technology,it was newly found that the addition of CO_(2)gas produced CaCO_(3)(li...Recently,we developed an innovative CO_(2)capture and storage method based on simple chemical reactions using NaOH and CaCl_(2).In this technology,it was newly found that the addition of CO_(2)gas produced CaCO_(3)(limestone)in the solution of NaOH and CaCl_(2)at less than 0.2 N NaOH,while at more than 0.2 N NaOH,Ca(OH)_(2)formation occurred merely without CO_(2).The present study has been designed to develop an integrated system in which the electrolysis unit is combined with the CO_(2)fixation unit.As the electrolysis of NaCl produces simultaneously not only electricity but also H_(2)and Cl_(2),the produced H_(2)could be supplied to the hydrogen generator to produce further electricity,which could be used for the initial NaCl electrolysis for NaOH production.Contrarily,the combination of incinerators with electrolytic generators has already been established to supply electricity,as thermal power plants use coals or wastes.This electricity-providing unit could be replaced with a solar panel plant or with a storage buttery.The present integrated system,consisting of various electricity-providing methods and CO_(2)fixation units,is a sustainable circulating energy system and carbon capture,usage,and storage(CCUS)system without environmental concerns.In addition,an unexpected-tremendous amount of the burned wood,which was produced by the big mountain or forest fires,could be disposed of by our integrated CO_(2)fixing system with the incinerator without environmental concerns along with both H_(2)and CaCO_(3)productions.Thus,our simple technology must contribute immediately and economically to disaster recovery.展开更多
Different treatment technologies have been efficiently applied to remove heavy metals from waste- water. Efforts have been made to find out the most economic water treatment technology by using low cost and easily acc...Different treatment technologies have been efficiently applied to remove heavy metals from waste- water. Efforts have been made to find out the most economic water treatment technology by using low cost and easily accessible natural materials. On the other hand, heavy metals are the most threatening groundwater contaminants because of their toxicity and harmful effects on human and biota. This review discusses the use of natural geological materials for heavy metal removal in aqueous systems. Special attention has been devoted to natural limestone through a systematic inventory of relevant published reports. The removal of toxic metals may include different mechanisms （e.g., physisorption, chemisorptions, precipitation, etc.）, depending on the physico-chemical properties of the material and the removed metal. Sorption of toxic metals （e.g., Pb, Cu, Cd, Zn, Cr, Hg, etc.） onto natural limestone involved precipitation of metal carbonate as a predominant removal process, but often subordinated by adsorption and ion exchange, depending on the physico-chemical properties of the studied limestone.展开更多
基金sponsored by the Doctoral Fund of Ministry of Education of China (Grant no.20105201110002)Research Fund of Guizhou Province and Doctoral Programme Fund of Guizhou University
文摘The molybdenum-nickel deposits in Shuidong District of Nayong County （Guizhou Province, Southwest China） are found mainly in black shale series of Lower Cambrian Niutitang Formation, which is another Mo-Ni-rich region besides Zunyi District （Guizhou province）. Our systematic study on the Mo-Ni deposits in Tangjiaba of Nayong reveals that layered coarse-grained limestones, spherical beaded limestones concretions are hosted at the lower seam of the Mo-Ni deposits. Its strong negative carbon isotope anomaly （the carbon isotope value of the coarse-grained limestones varies from -2.148‰ to 8.223‰） is similar to that in the modern submarine black smoker chimney. The carbon in the coarse-grained limestones from black rock series of Nayong County might be deep source inorganic carbon. The seams, coarse-grained limestones, ore-bearing coarse-grained limestones and the roof and floor of the deposits are characterized by co-variation on the trace element spider diagram, showing good homology. The extraordinary enrichment of Ag, As and Sb resembles hydrothermal sedimentation. Pro-Earth＇s core elements Se is strongly enriched in Ni-Mo ore-bearing coarse-grained limestones. The ore-bearing rock series has an extremely low Th/U value （0.012-0.19）; in the logU-logTh Cartesian Coordinates, the samples of the roof and floor of the deposits and ore-bearing coarse-grained limestones are found in the East Pacific tise; and the samples of coarse-grained limestones are found between the paleo-hydrothermal dedimentary area and the East Pacific tise. The chondrite-normalized rare earth element patterns of the Ni-Mo deposits show LREE enrichment, Ce negative anomaly, and Eu negative anomaly （which is supposed to be influenced by the deep magmatic processes in an extensional environment） resembles the rare earth element distribution patterns of the fluid and its sediments in modern submarine hydrothermal system. It proves that coarse-grained limestones is characterized by typical hydrothermal limestones, being closely related with the genesis of Mo-Ni deposits in Nayong County, which provides new evidence for hydrothermal sedimentary genesis of Mo-Ni deposit and negative carbon anomaly in the basal Cambrian on a global scale.
基金supported by the National Natural Science Foundation of China(grant number 51574208)the National 973 Program of China(grant number 2012CB214802)+1 种基金the China Geological Survery Project(grant number DD20190217)the China Scholar Council(grant number 201606400023)for providing the financial support
文摘This study examines the rare earth elements and yttrium(REY)concentrations of twenty-five samples from the reef outcrop exposed along the Lianglitage Mountain in the Ordovician,Tarim Basin in China.The concentration analysis provides constraints on the paleoenvironment during reef deposition.Based on the detailed sedimentology and petrographic work,we divide the reef facies into four sub-facies:the base facies,reef-core facies,reef-flank facies,and sealing facies.The geochemical data(such as major and trace elements,carbon and oxygen isotopes,and REYs)are further used to study the coeval seawater characteristics as well as potential diagenesis overprints.The result indicated that the diagenesis has little effect on the REY patterns of the reefal limestones.The REY concentrations of the reefal limestones are overall low(ranging from 3.69 to 19.60 ppm,arithmetic mean=10.22 ppm,SD=5.4).The PAAS-normalized REY patterns are consistently flat compared to the typical well-oxidized,shallow marine water patterns.However,the light REE(LREE)depletions,positive La anomalies,negative Ce anomalies and positive Y anomalies,suggest that these reefal limestones are likely an indicative of contemporaneous seawater REY signals.The seawater-like Y/Ho ratios(average at 37.51)further support that REY signals in these limestones are likely a reflection of seawater with little diagenetic modifications.The low Y/Ho ratios presented only in the reef-flank facies and sealing facies are likely a suggestion of detrital contamination.Hence,this study confirms that REY patterns of the limestones at the base facies and reef-core facies can record ancient seawater information,and reefs can be used as a potential geochemical proxy for paleoenvironment studies throughout the Earth’s history.
文摘The main aim of this work is to study the possibility of using different Emirati limestones for the production of quicklime. Representative limestone samples have been collected to represent the Triassic, Jurassic, Cretaceous, Eocene and Oligocene ages. The limestone samples have been characterized for their microstructure, mineral and chemical composition, physico-mechanical characteristics, thermal behavior using polarizing and scanning microscopes together with X-ray micro-tomography, XRD-IR, XRF, Archimedes and Mercury intrusion methods and DTA-TGA, respectively. Post characterization, the samples were fired in electrical muffle furnace for calcination under the firing conditions (800℃ to 1100℃) for (0.25 – 2 h). Then the lime grains have been characterized for their hydration rate, free lime content, pore-distribution and microfabric.
文摘This study presents an analysis of magnetic susceptibility and natural gamma radioactivity as indirect indicators of impurities in Cretaceous limestones of the Sabinas basin, as well as of the possible relation of these physical properties with the changes in the sedimentation environment. Both of these physical properties indicate changes in the degree of impurities and the mineralogical composition of this rock, principally in its organic matter and detritus content. Considering that the sedimentation environment determines the impurities in these rocks, possible environmental conditions at different levels of the Cretaceous were suggested using the magnetic susceptibility, total gamma radiation and potassium values, as well as the uranium and thorium concentration in the limestones. The analyses suggest variations in the depth of water table of the basin, which are mainly related to transgressions and marine regressions.
文摘Massive limestones were used in construction of ancient Egyptian tombs, temples, obelisks and other sculptures. These stones are always exposed to physico-mechanical deterioration and destructive forces, leading to partial or total collapse. The task of reassembling this type of artifacts represents a big challenge for the conservators. Recently, the researchers are turning to new technologies to improve the properties of traditional adhesive materials and techniques used in re-assembly of broken massive stones. The epoxy resins are used extensively in stone conservation and re-assembly of broken stones because of their outstanding mechanical properties. The adding of nanoparticles to polymeric adhesives at low percentages may lead to substantial improvements of their mechanical performances in structural joints and massive objects. The aim of this study is to evaluate the effectiveness of montmorillonite clay, calcium carbonate, and silicon dioxide nanoparticles for enhancing the performances of epoxy adhesives used in re-assembly of archaeological massive limestones. Scanning electron microscopy (SEM) was employed in order to investigate the morphology of the prepared nanocomposites, and the distribution of nanoparticles inside the composites. Artificial aging, tensile, compressive, and elongation strength tests were used to evaluate the efficiency of epoxy-nanocomposites. The results showed that the epoxy-clay nanocomposites exhibited superior tensile, compressive, and elongation strength, in addition to improving the mechanical properties of stone joints.
基金supported by the National Natural Science Foundation of China(Grant Nos.41977248 and 42207219)the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(CAS)(Grant No.IGGCAS-201903).
文摘Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conventional rocks both in terms of rock structure and mechanical properties. In this study, mesoscale uniaxial compression experiments with five different loading directions were conducted on two kinds of reef limestones from the Maldives Islands and the South China Sea, respectively. The real-time high-resolution videos and images of failure processes were recorded simultaneously to investigate the fracture evolution and fracture surface roughness of reef limestones. It demonstrated that the reef limestones belonged to extremely soft to soft rocks, and their uniaxial compressive strength (UCS) values fluctuated with high discreteness. The mesoscale mechanical properties of reef limestones were highly anisotropic and mainly controlled by pore structure. The occurrence of dissolution pores in reef limestone tended to intensify mechanical anisotropy. With the integration of the fracture initiation and propagation features of reef limestones, it is supposed that the intrinsic mechanism of anisotropy was probably attributed to the differences in coral growth direction and dissolution. Furthermore, the quantified fracture surface roughness was revealed to have a good consistency with density and UCS for the reef limestones from the South China Sea. The findings are helpful for providing theoretical and experimental references for engineering construction in coral reef areas.
文摘Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Eastern Pontides).They are well correlated with Aptian bitumen limestone in the other Tethys Reams.They are proposed as episodes of increased organic matter.However,background factors controlling organic matter enrichment are poorly known.In this study,we present new inorganic geochemistry,including trace elements,rare earth elements(REE),redox-sensitive elements(RSE),stable-isotopes(δ~(18)O andδ~(13)C),and total organic carbon(TOC).We integrated new geochemical data with existing stratigraphy,paleontology,and organic chemistry data to provide new insight into the depositional environment and paleoclimate conditions during Aptian.The lacustrine bitumen limestone(LBL)samples have variedδ~(13)C(ave.-1.45‰)andδ~(18)O(ave.-4.50‰).They possess distinct REE patterns,with an average of REE(ave.14.45 ppm)and Y/Ho(ave.35)ratios.In addition,they have variable Nd/YbN(0.28-0.81;ave.0.56)and Ce/Ce*(0.68-0.97;ave.0.86),and relatively high Eu^(*)/Eu(1.23-1.53;ave.1.35).They display seawater signatures with reduced oxygen conditions.The enrichment in RSE(Mo,Cu,Ni,and Zn)and the low Mo/TOC(0.70-3.69;ave.2.41)support a certain degree of water restriction.The high Sr/Ba,Sr/Cu,Ga/Rb,and K/Al records of the LBL facies suggest hot house climatic conditions.The sedimentary environment was probably an isolated basin that is transformed from the marine basin.In addition to depositional conditions,the regional parameters such as the climate,increased run-off period,nutrient levels,alkalinity level,and dominant carbonate producers favored the enrichment in organic matter of LBL facies.Thus,extreme greenhouse palaeoclimate conditions have an important role in organic matter enrichment in the isolated basin.Our results are conformable with the published data from marine,semi-restricted basin,and lacustrine settings in the different parts of the Tethys margin.Thus,this approach provides the first insight into the Aptian greenhouse paleo-climate conditions of the Eastern Black Sea Region,NE Turkey.
文摘The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction （chemical and mechanical）, internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these lime- stones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar car- bonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/ Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system.
基金The equipment of the Center for Collective Use“Geodynamics and Geochronology”of the Institute of the Earth’s Crust of the SB RAS was used in this work within the framework of the grant No.075-15-2021-682。
文摘Carbon and oxygen XRF spectra were studied using a WDXRF(WD X-ray fluorescence)spectrometer S8 TIGER(Bruker AXS,Germany).XRF spectra were obtained from the samples of the calcareous spar(CaCO3)(pure calcium carbonate),the limestones,the graphite,the microcrystalline cellulose,various organic compounds and prepared mixtures on the basis of the calcareous spar with addition of the graphite and the microcrystalline cellulose.The studied samples of the limestones are characterized by high concentrations of calcite(98.5-99%).Main objective of this investigation is to develop WDXRF technique for the determination of C(total)and O(total).Optimal instrumental measuring conditions were selected experimentally for quantitative determination of C(total)and O(total).The calculated values of the ILD(instrumental limit of the detection)vary from 0.0215%for C(total)to 0.0331%for O(total),respectively.The obtained values of the LDM(limit of determination of the XRF method)do not exceed 0.08%for C(total)and O(total).The RSDs(relative standard deviations)values do not exceed 1.0%in all cases.
文摘Limestones of different facies in the Senegal basin are most commonly used as aggregates, regardless of their petrographic properties. These differences may influence their behaviour. The aim of this paper is to study the stratigraphy and characterise the limestones of the Bandia and Popenguine quarries. Sampling and geochemical and geotechnical characterisation were carried out on these limestones. The results show the presence of several very different facies in the Paleocene formation. The geochemical study shows that the Bandia limestones (Bd2) have the highest CaCO<sub>3</sub> percentages (98.54%) and the highest SiO<sub>2</sub> percentages were recorded in the Popenguine limestones (Pop2). The study also gives MDE values of 22.38 and LA of 22, which are acceptable for use in road construction. It is important to carry out a complete study in order to select the right materials for optimal use.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(No.52279097,No.51779264)Blue and Green Project of Jiangsu Province.
文摘Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.
文摘Among the rolling hills and vineyards of the Tuscan countryside lies one of the most impressive tourist attractions not only in Italy,but in the entire world-a cascade(小瀑布)of white limestone pools overflowing with warm turquoise(绿松石色)water known as Cascate del Mulino.
基金financially supported by the Norwegian Ferroalloy Producers Research Association (FFF) and the Research Council of Norway through KSP project 326581 Recursive。
文摘The production processes for Si and FeSi have traditionally been considered slag-free.However,recent excavations have revealed significant accumulation of CaO–SiO_(2)–Al_(2)O_(3)slag within the furnaces.This accumulation can obstruct the flow of materials and gases,resulting in lower metal yield and higher energy consumption.The main objective of the current work is to enhance our understanding of slag formation during Si and FeSi production.We investigate slag formation through the dissolution of limestone and iron oxide in quartz and condensate,focusing on the reactions between these materials at a gram scale.Our findings indicate that most slag reaches equilibrium relatively quickly at temperatures starting from 1673 K.Notably,slag formation starts at lower temperature when the iron source is present (1573 K) compared to when only CaO is involved (1673 K).The minor elements tend to accumulate at quartz grain boundaries prior to slag formation.Furthermore,the slag produced from condensate contains less SiO_(2)than that generated from quartz with limestone.The type of quartz source and SiO_(2)phase appears to have little influence on slag formation.Good wettability is a significant factor in reaction between quartz and slag.FactSage calculations indicates that the viscosity of the slag ranges from 0.02 to 14.4 Pa·s under furnace conditions,comparable to the viscosity of honey or motor oil at room temperature.
基金Funded by the National Natural Science Foundation of China project(Nos.52108219 and U21A20150)the Lanzhou University of Technology Hongliu Outstanding Young Talent Program,China(No.04-062407)the Research on Quality Control Technology of High-performance Concrete Prepared by Manufactured Sand(No.2020Y21)。
文摘In view of the increased focus on“green”and sustainable development and compliance with the national strategy for“carbon peak and carbon neutrality,”this study investigated the effect of replacing cement(0-20%)with limestone powder(stone powder)as a mineral admixture on the micro,meso,and macro properties of mortar.First,the applicability of stone powder was examined based on the physical filling and heat of hydration of stone powder-cement.Second,micro-meso testing methods,such as X-ray diffraction,scanning electron microscopy,thermogravimetry-differential scanning calorimetry,and nuclear magnetic resonance,were utilized to reveal the influencing mechanisms of stone powder on the microstructure of the mortar.Furthermore,the effect of stone powder on the compressive strength and gas permeability of the mortar was analyzed.Additionally,the time-dependent variations in the gas permeability and its functional relationship with the mechanical properties were determined.Finally,the correlation between the compressive strength and gas permeability with respect to the pore size of stone powder-doped mortar was established via gray-correlation analysis.The results show that an appropriate amount of stone powder(5%)can effectively improve the particle gradation,decelerate the release of the heat of hydration,increase the amount of hydration products,and improve the pore structure,thereby increasing the compressive strength and reducing the gas permeability coefficient.The gas permeability of stone powder-doped mortar was found to exhibit good time-dependent characteristics as well as a quadratic linear correlation with the compressive strength.The gray-correlation analysis results indicate that air pores exhibit the highest influence on the compressive strength and that the gas permeability coefficient is most significantly affected by large pores.
基金supported by the National Natural Science Foundation of China(Grant Nos.41877267,41877260)the Priority Research Program of the Chinese Academy of Science(Grant No.XDA13010201).
文摘Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.
基金Supported by the National Natural Science Foundation of China(U23B20154)General Program of the National Natural Science Foundation of China(42372169)。
文摘In recent years,drilling data from wells Pengshen 10,Heshen 9,Tongshen 17 and Zhengyang 1 in the Sichuan Basin have confirmed the presence of a set of porous reef-beach limestone reservoirs in the Upper Permian Changxing Formation,which breaks the traditional view that deep carbonate oil and gas are only distributed in porous dolomite reservoirs and karst fracture-cavity limestone reservoirs.Through core and thin section observations,geochemical analysis,and well-seismic based reservoir identification and tracking,the study on formation mechanism of pores in deep reef-beach limestone reservoirs is carried out,this study provides insights in four aspects.(1)Porous reef-beach limestone reservoirs are developed in the Changxing Formation in deep-buried layers.The reservoir space is composed of intergranular pores,framework pores,intra-fossil pores,moldic pores and dissolution pores,which are formed in depositional and epigenetic environments.(2)The intermittently distributed porous reef-beach complexes are surrounded by relatively dense micrite limestone,which leads to the formation of local abnormal high-pressure inside the reef-beach complexes with the temperature increased.(3)The floor of the Changxing Formation reservoir is composed with interbedded tight mudstone and limestone of the Upper Permian Wujiaping Formation,and the roof is the tight micrite limestone interbedded with mudstone of the first member of Lower Triassic Feixianguan Formation.Under the clamping of dense roof and floor,the abnormal high-pressure in the Changxing Formation is formed.Abnormal high-pressure(overpressured compartment)is the key to maintain the pores formed in the depositional and epigenetic environments in deep-buried layers.(4)Based on the identification of roof,floor and reef-beach complexes,the favorable reef-beach limestone reservoir distribution area of 10.3×10^(4) km^(2) is predicted by well-seismic integration.These insights lay the theoretical foundation for the development of deep porous limestone reservoirs,expand the new field of exploration of deep-buried limestone reservoirs in the Sichuan Basin.
基金the funding support from Alpha Foundation for the Improvement of Mine Safety and Health Inc.(ALPHAFOUNDATION,Grant No.AFC820-52)。
文摘Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts.However,limited studies(mostly based on empirical field observation and small-scale laboratory tests)have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems.This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale(specimens with edge length of 0.5 m)for incorporation of actual support elements,with consideration of different w/h ratios.Both unsupported and supported(grouted rebar rockbolt and wire mesh)tests were conducted,and the surface deformations of the specimens were monitored using three-dimensional(3D)digital image correlation(DIC).Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution,load mobilization,and localized deformation at different w/h ratios.Both axial and bending strains were observed in the rockbolts,which became more prominent in the post-peak region of the stress-strain curve.
基金The financial support of the National Natural Science Foundation of China(Grant No.42030714)the National Key R&D Program of China(Grant No.2019YFC1509900)is greatly acknowledged.
文摘High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic binder,demonstrates significant potential for improving the engineering characteristics of such soils.Nevertheless,the impact of LC3 on the physico-mechanical characteristics of treated soil under a cyclic wet-dry environment remains unclear.This study for the first time investigates LC3's impact on the long-term durability of treated high-plastic clays through comprehensive macro-micro testing including physical,mechanical,mineralogical,and microstructural investigations with an emphasis on wet-dry cycles.The results revealed that LC3 treatment exhibits significant resistance to wet-dry cycles by completely mitigating the swelling potential,and a considerable reduction in plasticity resulting in enhanced workability.The compressibility and shear strength parameters have been significantly improved to several orders of magnitude.However,after six wet-dry cycles,a slight to modest reduction is observed,but overall durability remains superior to untreated soil.Cohesive and structural bonding ratios quantitatively assessed the impact of wet-dry cycles emphasizing the advantage of LC3 treatment.According to mineralogical and microstructural evaluation,the mechanism behind the adverse effects of wet-dry cycles on the compressibility and strength behavior of LC3-treated soil is mainly attributed to:(1)weakening of CSH/C(A)SH and ettringite(AFt)phases by exhibiting lower peak intensities;and(2)larger pore spaces due to repeated wet-dry cycles.These findings highlight LC3's performance in enhancing the long-term behavior and resilience of treated soils in real-world scenarios,providing durable solutions for infrastructure challenges.
文摘Recently,we developed an innovative CO_(2)capture and storage method based on simple chemical reactions using NaOH and CaCl_(2).In this technology,it was newly found that the addition of CO_(2)gas produced CaCO_(3)(limestone)in the solution of NaOH and CaCl_(2)at less than 0.2 N NaOH,while at more than 0.2 N NaOH,Ca(OH)_(2)formation occurred merely without CO_(2).The present study has been designed to develop an integrated system in which the electrolysis unit is combined with the CO_(2)fixation unit.As the electrolysis of NaCl produces simultaneously not only electricity but also H_(2)and Cl_(2),the produced H_(2)could be supplied to the hydrogen generator to produce further electricity,which could be used for the initial NaCl electrolysis for NaOH production.Contrarily,the combination of incinerators with electrolytic generators has already been established to supply electricity,as thermal power plants use coals or wastes.This electricity-providing unit could be replaced with a solar panel plant or with a storage buttery.The present integrated system,consisting of various electricity-providing methods and CO_(2)fixation units,is a sustainable circulating energy system and carbon capture,usage,and storage(CCUS)system without environmental concerns.In addition,an unexpected-tremendous amount of the burned wood,which was produced by the big mountain or forest fires,could be disposed of by our integrated CO_(2)fixing system with the incinerator without environmental concerns along with both H_(2)and CaCO_(3)productions.Thus,our simple technology must contribute immediately and economically to disaster recovery.
文摘Different treatment technologies have been efficiently applied to remove heavy metals from waste- water. Efforts have been made to find out the most economic water treatment technology by using low cost and easily accessible natural materials. On the other hand, heavy metals are the most threatening groundwater contaminants because of their toxicity and harmful effects on human and biota. This review discusses the use of natural geological materials for heavy metal removal in aqueous systems. Special attention has been devoted to natural limestone through a systematic inventory of relevant published reports. The removal of toxic metals may include different mechanisms （e.g., physisorption, chemisorptions, precipitation, etc.）, depending on the physico-chemical properties of the material and the removed metal. Sorption of toxic metals （e.g., Pb, Cu, Cd, Zn, Cr, Hg, etc.） onto natural limestone involved precipitation of metal carbonate as a predominant removal process, but often subordinated by adsorption and ion exchange, depending on the physico-chemical properties of the studied limestone.
