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Investigation on high-volume fly ash pastes modified with micro-size metakaolin subjected to high temperatures 被引量:1
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作者 Alaa M RASHAD 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第1期231-241,共11页
Portland cement(PC) containing high-volume fly ash(HVFA) is usually used to obtain economical and more sustainable merits, but these merits suffer from dramatically low compressive strength especially at early ages. I... Portland cement(PC) containing high-volume fly ash(HVFA) is usually used to obtain economical and more sustainable merits, but these merits suffer from dramatically low compressive strength especially at early ages. In this work, the possibility of using micro-size metakaolin(MSK) particles to improve the compressive strength of HVFA paste before and after subjecting to high temperatures was studied. To produce HVFA paste, cement was partially substituted with 70% fly ash(FA), by weight. After that, FA was partially substituted with MSK at ratios fluctuating from 5% to 20% with an interval of 5%, by weight. The effect of MSK on the workability of HVFA mixture was measured. After curing, specimens were subjected to different high temperatures fluctuating from 400 to 1000 ℃ with an interval of 200 ℃ for 2 h. The results were analyzed by different techniques named X-ray diffraction(XRD), thermogravimetry(TGA) and scanning electron microscopy(SEM). The results showed that the incorporation of MSK particles into HVFA mixture exhibited a negative effect on the workability and a positive effect on the compressive strength before and after firing. 展开更多
关键词 high-volume fly ash micro-size metakaolin high-temperature property workability remaining compressive strength
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High-Volume Fly Ash Concrete-A Relevant Step to Sustainable Development
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作者 Malgorzata Lelusz 《Journal of Environmental Science and Engineering(A)》 2014年第5期257-267,共11页
HVFA (high-volume fly ash) concrete could be a sustainable way for by-product utilization to conserve natural resources and protect environment. HVFA concrete can play the role of a high-performance material that ma... HVFA (high-volume fly ash) concrete could be a sustainable way for by-product utilization to conserve natural resources and protect environment. HVFA concrete can play the role of a high-performance material that may be comparable to the conventional Portland cement concrete. The results of the research programme concerning the relationships between the composition of concrete (w/b ratio, fly ash content and type of cement) and their physical and mechanical properties are presented and discussed in the paper. It is found that the introduction of high-volume fly ash into concrete has caused a decrease in compressive strength at the early age of storage. The significant increase in strength was observed between 28 days and 90 days of curing. The high-volume fly ash concretes were characterized with lower water absorbability and sorptivity than control concrete. 展开更多
关键词 fly ash concrete high-volume fly ash strength development.
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Accelerated Carbonation Assessment of High-Volume Fly Ash Concrete 被引量:1
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作者 Federico Aguayo Anthony Torres +1 位作者 Yoo-Jae Kim Omkar Thombare 《Journal of Materials Science and Chemical Engineering》 2020年第3期23-38,共16页
The issue of concrete carbonation has gained importance in recent years due to the increase use in supplementary cementing materials (SCMs) in concrete mixtures. While there is general agreement that concrete carbonat... The issue of concrete carbonation has gained importance in recent years due to the increase use in supplementary cementing materials (SCMs) in concrete mixtures. While there is general agreement that concrete carbonation progresses at maximum at a relative humidity of about 60%, the rate may differ in the case of cements blended with SCMs, especially with high-volume fly ash replacements. In this study, the effect of high-volume fly ash concrete exposed to low ambient relative humidity (RH) conditions (57%) and accelerated carbonation (4% CO2) is investigated. Twenty-three concrete mixtures were produced varying in cementitious contents (310, 340, 370, and 400 kg/m3), water-to-cementitious materials ratio (0.45 and 0.50), and fly ash content (0%, 15%, 30%, and 50%) using a low and high-calcium fly ash. The specimens were allowed 1 and 7 days of moist curing and monitored for their carbonation rate and depth through phenolphthalein measurements up to 105 days of exposure. The accelerated carbonation test results indicated that increasing the addition of fly ash also led to increasing the depth of carbonation. Mixtures incorporating high-calcium fly ash were also observed to be more resistant against carbonation than low-calcium fly ash due to the higher calcium oxide (CaO) content. However, mixtures incorporating high-volume additions (50%) specimens were fully carbonated regardless of the type of fly ash used. It was evident that the increase in the duration of moist curing from 1 day to 7 days had a positive effect, reducing the carbonation depth for both plain and blended fly ash concrete mixes, however, this effect was minimal in high-volume fly ash mixtures. The results demonstrated that the water-to-cementitious ratio (W/CM) had a more dramatic impact on carbonation resistance than the curing age for mixtures incorporating 30% or less fly ash replacement, whereas those mixtures incorporating 50% showed minor differences regardless of curing age or W/CM. Based on the compressive strength results, carbonation depth appeared to decrease with increase in compressive strength, but this correlation was not significant. 展开更多
关键词 Accelerated CARBONATION fly ash Concrete Relative Humidity high-volume fly ash SUPPLEMENTARY Cementitious Materials
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Preparation and Properties of Eco-Friendly Aerated Concrete Utilizing High-Volume Fly Ash with MgO and CaO Activators
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作者 Xiaoling Qu Xingshuo Yang +3 位作者 Siqi li Changan Tian Zaibo Li Zhiguang Zhao 《Journal of Renewable Materials》 SCIE EI 2022年第12期3335-3350,共16页
The associated MgO in limestone is believed to affect the volume stability of cementitious materials at room tem-perature,which limits the utilization of low grade limestone.In this study,MgO was used as an alkali act... The associated MgO in limestone is believed to affect the volume stability of cementitious materials at room tem-perature,which limits the utilization of low grade limestone.In this study,MgO was used as an alkali activator instead of partial CaO to prepare the aerated concrete under hydrother mal conditions.The expansion process was studied to evaluate the influence of the raw materials on the gas forming stability of the slurry.The pore structure(porosity,pore size and its distribution)was analyzed by the image method.The physic mechanical properties(density,strength,thermal properties)of concrete with the addition of MgO were comprehensively investigated.Besides,the mineral compositions and morphology of the hydration products were analyzed to demonstrate the infuence mechanism of MgO on the mechanical properties.Experimental results show that the final expansion rate of the slurry decreases with MgO content.A reasonable MgO content,ie,MgO/(MgO+CaO)<20%,con-tributes to improve the compressive strength,attributing to an increased reaction rate to C-S-H gel and tobermor-ite.The addition of MgO causes the thermal conductivity and specific heat to increase.The pore structure is mainly related to the amount of air entraining agent.This study has a significance for the further utilization of magnesium-rich carbonates in the autoclaved building products. 展开更多
关键词 fly ash aerated concrete strength thermal properties pore structure
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Mechanism study of Cu(Ⅱ) adsorption from acidic wastewater by ultrasonic-modified municipal solid waste incineration fly ash
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作者 Shunda lin Yang Lu +3 位作者 Lin Zheng Ling Long Xuguang Jiang Jianhua Yan 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第3期157-165,共9页
High concentrations of copper ions(Cu(Ⅱ)) in water will pose health risks to humans and the ecological environment. Therefore, this study aims to utilize ultrasonic-cured modified municipal solid waste incineration(M... High concentrations of copper ions(Cu(Ⅱ)) in water will pose health risks to humans and the ecological environment. Therefore, this study aims to utilize ultrasonic-cured modified municipal solid waste incineration(MSWI) fly ash for Cu(Ⅱ) adsorption to achieve the purpose of “treating waste by waste.” The effects of p H, adsorption time, initial concentration, and temperature on the modified MSWI fly ash’s adsorption efficiency were systematically studied in this article. The adsorption performance of the modified MSWI fly ash can be enhanced by the ultrasonic modification. At pH = 2, 3 and 4, the adsorption capacity of the modified MSWI fly ash for Cu(Ⅱ) increased by 2.7, 1.9 and 1.2 times, respectively. Furthermore, it was suggested that the adsorption process of the modified MSWI fly ash can be better simulated by the pseudo-second-order kinetic model, with a maximum adsorption capacity calculated by the Langmuir model of 24.196 mg.g-1. Additionally, the adsorption process is spontaneous,endothermic, and chemisorption-dominated from the thermodynamic studies(ΔH and ΔS > 0, ΔG < 0).Finally, the enhanced adsorption performance of the modified MSWI fly ash for Cu(Ⅱ) may be attributed to electrostatic interaction and chelation effects. 展开更多
关键词 ULTRASOUND MSWI fly ash Cu(Ⅱ) WASTEWATER ADSORPTION
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Effect of Na_(2)CO_(3)Roasting Activation on Acid Leaching Property of Fly Ash
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作者 LIU Chenjia ZHAO Aichun +4 位作者 YE Xin ZHAO Zi ZHANG Tingan YANG Xiaorong QIN Yanmei 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2024年第6期1613-1620,共8页
By using high-alumina fly ash as raw material,a process was proposed for activating the fly ash with Na_(2)CO_(3)calcination and extracting aluminum from activated clinker with sulfuric acid leaching.The feasibility o... By using high-alumina fly ash as raw material,a process was proposed for activating the fly ash with Na_(2)CO_(3)calcination and extracting aluminum from activated clinker with sulfuric acid leaching.The feasibility of roasting process of activated fly ash by Na_(2)CO_(3)was discussed based on thermodynamic analysis.The experimental results showed that Na_(2)CO_(3)gradually reactes with mullite over 700 K to produce NaAlSiO_(4).The optimal process conditions for the activation stage are:a material ratio of 1:1 between sodium carbonate and fly ash,a calcination temperature of 900℃,and a calcination time of 2.5 hours.Under these conditions,the leaching rate of aluminum is 90.3%.By comparing the SEM and XRD analysis of raw and clinker materials,it could be concluded that the mullite phase of fly ash is almost completely destroyed and transformed into sodium aluminosilicate with good acid solubility. 展开更多
关键词 fly ash calcination activation acid leaching ALUMINUM
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A mini review on the separation of Al,Fe and Ti elements from coal fly ash leachate
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作者 Yuan Shi Fengqi Jiang +3 位作者 Rongjiao Wang Sasha Yang Xiaofeng Zhu Yingying Shen 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第2期1-15,共15页
The electricity demand is increasing rapidly with the development of society and technology.Coal-fired thermal power plants have become one of the primary sources of electricity generation for urbanization.However,coa... The electricity demand is increasing rapidly with the development of society and technology.Coal-fired thermal power plants have become one of the primary sources of electricity generation for urbanization.However,coal-fired thermal power plants produce a great amount of by-product coal fly ash every year.Coal fly ash disposal in landfills requires a sizable space and has negative environmental impacts.Therefore,it is crucial to develop new technologies and methods to utilize this enormous volume of solid waste in order to protect the environment.In this review,the fundamental physical and chemical character-istics of coal fly ash are introduced,and afterward the disposal policies and utilization ways of coal fly ash are discussed to gain a comprehensive understanding of the various ways this waste.The leaching of valuable metals in coal fly ash and the extraction of metal elements in leachate under different conditions are also summarized.Furthermore,the possibility of coal fly ash to serve as a supplementary source for mineral resources is analyzed,providing a basis for its extensive use as a raw material in the metal industry in China and worldwide. 展开更多
关键词 Coal fly ash Waste utilization Metals extraction
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Solvothermal synthesis and adsorption performance of layered boehmite using aluminum chloride and high-alumina fly ash
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作者 Jing Wen Ruirui Yuan +2 位作者 Tao Jiang Tangxia Yu Yufan Zhang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第6期280-290,共11页
High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina con... High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina containing leaching solution obtained from Na_(2)CO_(3) roasting and HCl leaching of FAHAl was used as the mother liquor to prepare layered boehmite in situ.The preparation process with AlCl_(3) as the raw material was also compared.The formation process and mechanism of boehmite,the choice of solvent,along with the adsorption capability of Congo red were analyzed by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,Brunauer-Emmett-Teller method and adsorption experiments.Results showed that during the preparation of layered boehmite,the precursor Al(OH)_(3) from the reaction of Al^(3+) and OH-is transformed into boehmiteγ-AlOOH.The existence of ethanol is beneficial to regulate and promote the growth of boehmite crystal effectively.When water and ethanol are mixed with a volume ratio of 2:1 and used as the solvent,the maximum specific surface area of the boehmite is obtained at 135.7 m^(2)·g^(-1),and 99.16%of Congo red can be absorbed after 10 min when AlCl3 is used as a raw material.As purified leaching solution is used as the mother liquid,the crystallinity of boehmite decreases slightly when the pH value decreases from 12.5 to 11.When pH is 11,the removal efficiency of Congo red reaches a maximum of 72.25%.This process not only achieves the extraction of aluminum and high-value utilization of FAHAl but also provides a thought to prepare layered boehmite with adsorption properties. 展开更多
关键词 High-alumina fly ash Layered boehmite In-situ preparation Solvothermal synthesis Adsorption High-value utilization
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Synergistic CO_(2) mineralization using coal fly ash and red mud as a composite system
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作者 Zhenchao Yao Yugao Wang +3 位作者 Jun Shen Yanxia Niu Jiang Feng Yang Xianyong Wei 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第3期149-158,共10页
CO_(2) mineralization plays a critical role in the storage and utilization of CO_(2).Coal fly ash(CFA)and red mud(RM)are widely utilized as CO_(2) mineralizers.However,the inert calcium species in CFA limit its carbon... CO_(2) mineralization plays a critical role in the storage and utilization of CO_(2).Coal fly ash(CFA)and red mud(RM)are widely utilized as CO_(2) mineralizers.However,the inert calcium species in CFA limit its carbonation capacity,meanwhile the substantial Ca^(2+)releasing of RM is hindered by a covering layer of calcium carbonate.In this study,CO_(2) mineralization in a composite system of CFA and RM was investigated to enhance the carbonation capacity.Multiple analyzers were employed to characterize the raw materials and resulting mineralization products.The results demonstrated that a synergistic effect existed in the composite system of CFA and RM,resulting in improving CO_(2) mineralization rate and efficiency.The produced calcium carbonate was ectopically attached the surface of CFA in the composite system,thus slowing down its coverage on the surface of RM.This phenomenon facilitated further releasing Ca^(2+)from the internal RM,thereby enhancing CO_(2) mineralization efficiency.Meanwhile,the inclusion of RM significantly improved the alkalinity of the composite system,which not only promoted the dissolution of Ca^(2+)of the inert CaSO_(4)(H_(2)O)_(2) in CFA,but also accelerated CO_(2) mineralization rate.The investigation would be beneficial to CO_(2) mineralization using industrial solid wastes. 展开更多
关键词 CO_(2)mineralization Coal fly ash Red mud Synergistic effect
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Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers
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作者 Qiyao Yang Xiaobin Qi +1 位作者 Qinggang Lyu Zhiping Zhu 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第1期8-18,共11页
Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environmen... Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage. 展开更多
关键词 Circulating fluidized bed Coal gasification fly ash Steam activation Pore structure evolution Fluidization activation
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Combined use of fly ash and silica to prevent the long-term strength retrogression of oil well cement set and cured at HPHT conditions
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作者 Guo-Dong Cheng Xue-Yu Pang +4 位作者 Jin-Sheng Sun Zheng-Song Qiu Chuang-Chuang Wang Jian-Kun Qin Ning Li 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期1122-1134,共13页
The long-term strength retrogression of silica-enriched oil well cement poses a significant threat to wellbore integrity in deep and ultra-deep wells, which is a major obstacle for deep petroleum and geothermal energy... The long-term strength retrogression of silica-enriched oil well cement poses a significant threat to wellbore integrity in deep and ultra-deep wells, which is a major obstacle for deep petroleum and geothermal energy development. Previous attempts to address this problem has been unsatisfactory because they can only reduce the strength decline rate. This study presents a new solution to this problem by incorporating fly ash to the traditional silica-cement systems. The influences of fly ash and silica on the strength retrogression behavior of oil well cement systems directly set and cured under the condition of 200°C and 50 MPa are investigated. Test results indicate that the slurries containing only silica or fly ash experience severe strength retrogression from 2 to 30 d curing, while the slurries containing both fly ash and silica experience strength enhancement from 2 to 90 d. The strength test results are corroborated by further evidences from permeability tests as well as microstructure analysis of set cement. Composition of set cement evaluated by quantitative X-ray diffraction analyses with partial or no known crystal structure(PONKCS) method and thermogravimetry analyses revealed that the conversion of amorphous C-(A)-S-H to crystalline phases is the primary cause of long-term strength retrogression.The addition of fly ash can reduce the initial amount of C-(A)-S-H in the set cement, and its combined use with silica can prevent the crystallization of C-(A)-S-H, which is believed to be the working mechanism of this new admixture in improving long-term strength stability of oil well cement systems. 展开更多
关键词 fly ash Long-term strength retrogression High temperature Quantitative X-ray diffraction(QXRD) Partial or no known crystal structure(PONKCS)
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Study on Fly Ash Based Porous Ceramsite as Biological Filter Media
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作者 Ruigang WANG Shuo WANG +1 位作者 Weijie LI Hailong LIU 《Agricultural Biotechnology》 2024年第1期71-73,共3页
Using fly ash as a raw material,porous ceramic particles with an apparent density of 1.21 g/cm^(3),a visible porosity of 51.03%,and a specific surface area of 4.26 m^(2)/g were prepared and used as biofilter materials... Using fly ash as a raw material,porous ceramic particles with an apparent density of 1.21 g/cm^(3),a visible porosity of 51.03%,and a specific surface area of 4.26 m^(2)/g were prepared and used as biofilter materials for wastewater treatment.Through SEM,XRD analysis,and heavy metal leaching analysis,it was found that porous ceramsite were porous materials with rough surfaces.After calcination,the newly formed mineral was silicate calcium feldspar.The heavy metal concentration in the leaching solution of porous ceramsite met the national surface water quality requirements.The treatment of domestic sewage showed that the volumetric loads of COD Cr,NH_(4)^(+)-N,and TN removed by the aerated biofilter were 5.23,0.98,and 0.35 kg/(m^(3)·d),respectively,with removal rates of 85.46%,96.13%,and 32.31%. 展开更多
关键词 Porous ceramsite Domestic sewage fly ash
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A Study on the Effect of Low Calcium Ultra-fine Fly Ash as a Partial Sustainable Supplementary Material to Cement in Self-compacting Concrete 被引量:2
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作者 Adapala Sunny Suprakash Karthiyaini S 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2023年第2期330-341,共12页
The aim and scope of the present study were to determine the efficacy of UFFA in evaluating the workability,static and dynamic stabilization properties,retention period,and slump loss of SCC systems in their fresh sta... The aim and scope of the present study were to determine the efficacy of UFFA in evaluating the workability,static and dynamic stabilization properties,retention period,and slump loss of SCC systems in their fresh state,as well as their compressive strength at various ages.Microstructure(SEM and XRD)of blended SCC systems were studied.Also,the thermogravimetry behavior of blended SCC specimens were researched.According to the evaluated results,incorporating up to 20%UFFA into fresh concrete improved its performance due to its engineered fine particle size and spherical geometry,both of which contribute to the enhancement of characteristics.Blends of 25%and 30%of UFFA show effect on the water-binder ratio and chemical enhancer dosage,resulting in a loss of homogeneity in fresh SCC systems.The reduced particle size,increased amorphous content,and increased surface area all contribute to the pozzolanic reactivity of the early and later ages,resulting in denser packing and thus an increase in compressive strength.The experimental results indicate that UFFA enhances the properties of SCC in both its fresh and hardened states,which can be attributed to the particles’fineness and their relative effect on SCC. 展开更多
关键词 ultra fine fly ash self-compacting concrete WORKABILITY SEGREGATION compressive strength microstructure TGA
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Enhancing fly ash utilization in backfill materials treated with CO_(2)carbonation under ambient conditions 被引量:3
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作者 Ichhuy Ngo Liqiang Ma +1 位作者 Jiangtao Zhai Yangyang Wang 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2023年第3期323-337,共15页
The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-bas... The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-based backfill(CFBF)material under ambient conditions.The performance of CFBF was investigated for different fly ash-cement ratios and compared with non-CO_(2)reacted samples.The fresh CFBF slurry conformed to the Herschel-Bulkley model with shear thinning characteristics.After carbonation,the yield stress of the fresh slurry increased significantly by lowering fly ash ratio due to gel formation.The setting times were accelerated,resulting in approximately 40.6%of increased early strength.The final strength decreased when incorporating a lower fly ash ratio(50%and 60%),which was related to the existing heterogeneous pores caused by rapid fluid loss.The strength increased with fly ash content above 70%because additional C-S(A)-H and silica gels were characterized to precipitate on the grain surface,so the binding between particles increased.The C-S(A)-H gel was developed through the pozzolanic reaction,where CaCO_(3)was the prerequisite calcium source obtained in the CO_(2)-fly ash reaction.Furthermore,the maximum CO_(2)uptake efficiency was 1.39 mg-CO_(2)/g-CFBF.The CFBF material is feasible to co-dispose CO_(2)and fly ash in the mine goaf as negative carbon backfill materials,and simultaneously mitigates the strata movement and water lost in post-subsurface mining. 展开更多
关键词 fly ash utilization CO_(2)carbonation Ambient conditions Water conservative backfill mining Negative carbon backfill materials
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Molecular mechanism of fly ash affecting the performance of cemented backfill material 被引量:1
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作者 Shuo Yang Jiangyu Wu +5 位作者 Hongwen Jing Xinguo Zhang Weiqiang Chen Yiming Wang Qian Yin Dan Ma 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第8期1560-1572,共13页
The great challenge of cemented tailings backfill(CTB)is difficult simultaneously maintaining its excellent mechanical properties and low cost.Fly ash(FA)can potentially address this problem and further replace cement... The great challenge of cemented tailings backfill(CTB)is difficult simultaneously maintaining its excellent mechanical properties and low cost.Fly ash(FA)can potentially address this problem and further replace cement in favor of low carbon development.However,its mechanism on CTB with low cement dosage and low Ca system remains unclear.Consequently,this study conducted uniaxial compression,Xray diffraction(XRD),and scanning electron microscopy(SEM)-energy dispersive spectrometer(EDS)tests to investigate the effect of FA dosage on the mechanical property and microstructure of CTB.A molecular model of FA-CSH was constructed to reproduce the molecular structure evolution of CTB with FA based on the test results.The influences of FA dosage and calcium/silica molar ratio(Ca/Si ratio)on the matrix strength and failure model were analyzed to reveal the mechanism of FA on calcium silicate hydrated(C-S-H).The results show that the strength of CTB increases initially and then decreases with FA dosage,and the FA supplement leads to a decrease in Ca(OH)_(2) diffraction intensity and Ca/Si ratio around the FA particles.XRD and SEM-EDS findings show that the Ca/Si ratio of C-S-H decreases with the progression of hydration.The FA-CSH model indicates that FA can reinforce the silica chain of C-S-H to increase the matrix strength.However,this enhancement is weakened by supplementing excessive FA dosage.In addition,the hydrogen bonds among water molecules deteriorate,reducing the matrix strength.A low Ca/Si ratio results in an increase in water molecules and a decrease in the ionic bonds combined with Ca^(2+).The hydrogen bonds among water molecules cannot withstand high stresses,resulting in a reduction in strength.The water absorption of the FA-CSH model is negatively correlated with the FA dosage and Ca/Si ratio.The use of optimal FA dosage and Ca/Si ratio leads to suitable water absorption,which further affects the failure mode of FA-CSH. 展开更多
关键词 fly ash cemented tailings backfill calcium/silica ratio microstructure molecular dynamics simulation
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An Experimental Investigation on Workability and Bleeding Behaviors of Cement Pastes Doped with Nano Titanium Oxide (n-TiO 2) Nanoparticles and FlyAsh 被引量:1
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作者 FatihÇelik Oğuzhan Yıldız +1 位作者 AndaçBaturÇolak Samet Mufit Bozkır 《Fluid Dynamics & Materials Processing》 EI 2023年第1期135-158,共24页
In this study,the workability of cement-based grouts containing n-TiO 2 nanoparticles and fly ash has been investigated experimentally.Several characteristic quantities(including,but not limited to,the marsh cone flow... In this study,the workability of cement-based grouts containing n-TiO 2 nanoparticles and fly ash has been investigated experimentally.Several characteristic quantities(including,but not limited to,the marsh cone flow time,the mini slump spreading diameter and the plate cohesion meter value)have been measured for different percentages of these additives.The use of fly ash as a mineral additive has been found to result in improvements in terms of workability behavior as expected.Moreover,if nano titanium oxide is also used,an improvement can be obtained regarding the bleeding values for the cement-based grout mixes.Using such experimental data,a multi-layer perceptron artificial neural network model has been developed(5 neurons in the hidden layer of the network model have been developed using a total of 42 experimental data).70%of the data employed in this model have been used for training,15%for validation and 15%for the test phase.The results demonstrate that the artificial neural network model can predict Marsh cone flow time,mini slump spreading diameter and plate cohesion meter values with an average error of 0.15%. 展开更多
关键词 Nano titanium oxide fly ash workability of grouts BLEEDING stability of grouts ANN
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Waste fly ash-ZnO as a novel sunlight-responsive photocatalyst for dye discoloration
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作者 Leena V.Bora Sonal P.Thakkar +1 位作者 Kevin S.Vadaliya Nisha V.Bora 《Water Science and Engineering》 EI CAS CSCD 2023年第1期76-82,共7页
Treating waste with a waste material using freely available solar energy is the most effective way towards sustainable future.In this study,a novel photocatalyst,partly derived from waste material from the coal indust... Treating waste with a waste material using freely available solar energy is the most effective way towards sustainable future.In this study,a novel photocatalyst,partly derived from waste material from the coal industry,was developed.Fly ash hybridized with ZnO(FAeZn)was synthesized as a potential photocatalyst for dye discoloration.The synthesized photocatalyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and ultravioletevisible/near infra-red spectroscopy.The photocatalytic activity was examined with the discoloration of methylene blue used as synthetic dye wastewater.All the experiments were performed in direct sunlight.The photocatalytic performance of FAeZn was found to be better than that of ZnO and the conventionally popular TiO2.The LangmuireHinshelwood model rate constant values of ZnO,TiO2,and FAeZn were found to be 0.016 min1,0.017 min1,and 0.020 min1,respectively.There were two reasons for this:(1)FAeZn was able to utilize both ultraviolet and visible parts of the solar spectrum,and(2)its BrunauereEmmetteTeller surface area and porosity were significantly enhanced.This led to increased photon absorption and dye adsorption,thus exhibiting an energy-efficient performance.Therefore,FAeZn,partly derived from waste,can serve as a suitable material for environmental remediation and practical solar energy applications. 展开更多
关键词 PHOTOCATALYST ZNO fly ash GEOPOLYMER Wastewater treatment Methylene blue
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Fabrication of a flexible microwave absorber sheet based on a composite filler with fly ash as the core filled silicone rubber
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作者 Qiuying Li Yiheng Lu Zhuoyan Shao 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第3期548-558,共11页
A new type of composite filler was designed by a modified sol-gel method using fly ash(FA),Fe(NO_(3))_(3)·9H_(2)O,and Ni(NO_(3))_(2)·6H_(2)O as raw materials.The composite filler was a spherical core-shell s... A new type of composite filler was designed by a modified sol-gel method using fly ash(FA),Fe(NO_(3))_(3)·9H_(2)O,and Ni(NO_(3))_(2)·6H_(2)O as raw materials.The composite filler was a spherical core-shell structure composed of FA as the core and NiFe_(2)O_(4)as the shell.Further,the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials;X-ray diffraction,fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and scanning electron microscope confirmed that NiFe_(2)O_(4)was successfully coated on the surface of FA and formed a uniform and continuous coating layer.As expected,silicone rubber filled with the composite filler had a minimum reflection loss of-23.8 dB at 17.5 GHz with the thickness of 1.8 mm,while the effective absorption bandwidth was as high as 12 GHz.The addition of the composite filler greatly enhanced the microwave absorption properties of the system,which was resulted from multiple losses mechanism:interface polarization losses,magnetic losses,and multiple reflection losses.Also,silicone rubber filled with the composite filler exhibited excellent thermal stability,flexibility,environmental resistance,and hydrophobicity compared with traditional silicone rubber.Therefore,this work not only responds to the green chemistry to achieve efficient FA recovery,but also devises a new strategy to prepare microwave absorption materials with strong potential for civilian applications. 展开更多
关键词 fly ash microwave absorption silicone rubber multiple losses mechanism
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A Machine-Learning Approach for the Prediction of Fly-Ash Concrete Strength
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作者 Shanqing Shao Aimin Gong +4 位作者 Ran Wang Xiaoshuang Chen Jing Xu Fulai Wang Feipeng Liu 《Fluid Dynamics & Materials Processing》 EI 2023年第12期3007-3019,共13页
The composite exciter and the CaO to Na_(2)SO_(4) dosing ratios are known to have a strong impact on the mechanical strength offly-ash concrete.In the present study a hybrid approach relying on experiments and a machi... The composite exciter and the CaO to Na_(2)SO_(4) dosing ratios are known to have a strong impact on the mechanical strength offly-ash concrete.In the present study a hybrid approach relying on experiments and a machine-learn-ing technique has been used to tackle this problem.The tests have shown that the optimal admixture of CaO and Na_(2)SO_(4) alone is 8%.The best 3D mechanical strength offly-ash concrete is achieved at 8%of the compound activator;If the 28-day mechanical strength is considered,then,the best performances are obtained at 4%of the compound activator.Moreover,the 3D mechanical strength offly-ash concrete is better when the dosing ratio of CaO to Na_(2)SO_(4) in the compound activator is 1:1;the maximum strength offly-ash concrete at 28-day can be achieved for a 1:1 ratio of CaO to Na_(2)SO_(4) by considering a 4%compound activator.In this case,the compressive andflexural strengths are 260 MPa and 53.6 MPa,respectively;the mechanical strength offly-ash concrete at 28-day can be improved by a 4:1 ratio of CaO to Na_(2)SO_(4) by considering 8%and 12%compound excitants.It is shown that the predictions based on the aforementioned machine-learning approach are accurate and reliable. 展开更多
关键词 fly ash compound activator machine-learning approach
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Effect of CSH Crystal Nucleus on Steam-Free Cured Fly Ash Precast Concrete Components
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作者 Ruyi Luo Yanyan Hu +2 位作者 Tingshu He Xiaodong Ma Yongdong Xu 《Journal of Renewable Materials》 EI 2023年第9期3485-3500,共16页
The measures of steam curing and early-strengthening agents to promote the precast components to reach the target strength quickly can bring different degrees of damage to the concrete.Based on this,the new nanomateri... The measures of steam curing and early-strengthening agents to promote the precast components to reach the target strength quickly can bring different degrees of damage to the concrete.Based on this,the new nanomaterial CSH-the hydration product of cement effectively solves these measures’disadvantages,such as excessive energy consumption,thermal stress damage,and the introduction of external ions.In this paper,the effect of CSH on the early strength of precast fly ash concrete components was investigated in terms of setting time,workability,and mechanical properties and analyzed at the microscopic level using hydration temperature,XRD,and SEM.The results showed that under the same workability,CSH could significantly reduce the amount of admixture,shorten the final setting time,almost not affect the initial setting time,and accelerate the hydration of cement.At the optimum dose of 5%,the mechanical properties of the specimens were improved by more than 98%within 12 h of hydration,resulting in an earlier release time of 12 h and no risk of strength inversion later.The results of this paper give theoretical support to the behavior of precast components under steam-free curing. 展开更多
关键词 fly ash concrete prefabricated components steam-free curing CSH crystal nucleus TOBERMORITE
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