We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corre...We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.展开更多
Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescen...Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores （and volume） will lead to more intensive efflorescence.展开更多
Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investiga...Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investigated in detail on the molecular level, including ion and molecule interactions in supersaturated aerosols, metastable solid phases that may be formed, and microscopic structures and deliquescence mechanisms of aerosol particles. This paper presents a summary of the progress made in recent investigations of deliquescence and efflorescence processes of aerosol particles by four common spectral techniques, which are known as Raman/electrodynamic balance, Fourier transform infrared/aerosol flow tube, Fourier transform infrared/attenuated total reftection, and confocal Raman on a quartz substrate.展开更多
When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence...When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.展开更多
This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>...This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.展开更多
In the mining process of coal mine,waterproof coal pillars should be set between the weathered oxidation zone and the first mining face.In order to determine the reasonable upper limit of the first mining face of Hong...In the mining process of coal mine,waterproof coal pillars should be set between the weathered oxidation zone and the first mining face.In order to determine the reasonable upper limit of the first mining face of Hongyi Coal Mine,the waterproof coal pillar needs to be wide enough to resist the lateral hydrostatic pressure of the oxidation zone,and to ensure that the top plate aquifer does not run through the water guide crack zone,while also liberating as much stagnant coal as possible.In this paper,the first coal mine face’s waterproof coal pillar was calculated using conventional and optimized calculation methods,taking into account the dip angle of the coal seam,the height of the water-guide crack zone,and the rock shift influence zone,and finally the upper limit of the first face of Hongyi Coal Mine was determined.展开更多
FTIR-ATR technology is used to study the efflorescence kinetic of Na2SO4 and mixed Na2SO4/CTAB aerosols.As the RH decreased linearly,the v3-SO42 band shifts from 1094 cm1 to 1132 cm1,suggesting the phase transition of...FTIR-ATR technology is used to study the efflorescence kinetic of Na2SO4 and mixed Na2SO4/CTAB aerosols.As the RH decreased linearly,the v3-SO42 band shifts from 1094 cm1 to 1132 cm1,suggesting the phase transition of Na2SO4 from solution to crystal phase（Ⅲ）.For pure Na2SO4 aerosols,the ERH is 75.1%RH,whereas the efflorescence point of mixed Na2SO4/CTAB aerosols（74.2%） is lower.By further analysis of IR differential spectra,the ratio of Na2SO4 crystals in mixed aerosols is only 62.7%and the heterogeneous nucleation rate of Na2SO4 in Na2SO4/CTAB mixed aerosols is lower than that in pure Na2SO4 aerosols.They showed that CTAB assembled into reversed micelle and part Na2SO4 droplets are in the core to form core-shell structure,and CTAB shell prevents core Na2SO4 solutions from crystallizing.However,the counter ion Br for CTAB reversed micelle can interact with Na＋ ions,which decreases the crystallization rate of free Na2SO4 droplets and ERH is delayed.展开更多
基金Funded by the National Key Research and Development Program of China(No.2022YFC3803400)National Natural Science Foundation of China(Nos.52378255,52278270)+1 种基金Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Fundamental Research Funds for the Central Universities and the Experimental Center of Materials Science and Engineering in Tongji University。
文摘We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.
基金Funded by the Jiangsu Higher Education Institutions for a project PAPD(Priority Academic Program Development),Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)(No.IRT1146)+1 种基金Graduate Education Innovation Project in Jiangsu Province(No.CXLX13_409)supported by University of Southern Queensland and an ARC-linkage project
文摘Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores （and volume） will lead to more intensive efflorescence.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20073004, No.20473012, No.20673010, and No.20640420450）, the 111 Project B07012, and the China Postdoctoral Science Foundation （No.20070410466）. The Trans-Century Training Program Foundation for the Talents by the Ministry of Education of China was also gratefully acknowledged.
文摘Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investigated in detail on the molecular level, including ion and molecule interactions in supersaturated aerosols, metastable solid phases that may be formed, and microscopic structures and deliquescence mechanisms of aerosol particles. This paper presents a summary of the progress made in recent investigations of deliquescence and efflorescence processes of aerosol particles by four common spectral techniques, which are known as Raman/electrodynamic balance, Fourier transform infrared/aerosol flow tube, Fourier transform infrared/attenuated total reftection, and confocal Raman on a quartz substrate.
文摘When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.
文摘This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.
基金the Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(Grant No.GJNY-18-73.15)the National Natural Science Foundation of China(NSFC)under grant No.41602254+2 种基金the National Natural Science Foundation of China(NSFC)under grant No.41807221the Science and Technology Innovation Project of Northwest A&F University,the Double-Class Discipline Group Dry Area Hydrology and Water Resources Regulation Research funding project(Z102022011)the Special Funding Project for Basic Scientific Research Business Fees of Central Universities(2452016179).
文摘In the mining process of coal mine,waterproof coal pillars should be set between the weathered oxidation zone and the first mining face.In order to determine the reasonable upper limit of the first mining face of Hongyi Coal Mine,the waterproof coal pillar needs to be wide enough to resist the lateral hydrostatic pressure of the oxidation zone,and to ensure that the top plate aquifer does not run through the water guide crack zone,while also liberating as much stagnant coal as possible.In this paper,the first coal mine face’s waterproof coal pillar was calculated using conventional and optimized calculation methods,taking into account the dip angle of the coal seam,the height of the water-guide crack zone,and the rock shift influence zone,and finally the upper limit of the first face of Hongyi Coal Mine was determined.
基金financially supported by the National Natural Science Foundation of China (Nos. 21373026, 21473009.)
文摘FTIR-ATR technology is used to study the efflorescence kinetic of Na2SO4 and mixed Na2SO4/CTAB aerosols.As the RH decreased linearly,the v3-SO42 band shifts from 1094 cm1 to 1132 cm1,suggesting the phase transition of Na2SO4 from solution to crystal phase（Ⅲ）.For pure Na2SO4 aerosols,the ERH is 75.1%RH,whereas the efflorescence point of mixed Na2SO4/CTAB aerosols（74.2%） is lower.By further analysis of IR differential spectra,the ratio of Na2SO4 crystals in mixed aerosols is only 62.7%and the heterogeneous nucleation rate of Na2SO4 in Na2SO4/CTAB mixed aerosols is lower than that in pure Na2SO4 aerosols.They showed that CTAB assembled into reversed micelle and part Na2SO4 droplets are in the core to form core-shell structure,and CTAB shell prevents core Na2SO4 solutions from crystallizing.However,the counter ion Br for CTAB reversed micelle can interact with Na＋ ions,which decreases the crystallization rate of free Na2SO4 droplets and ERH is delayed.
