Microwave-curing and mechanical grinding of fly ash have both beenadopted as effective methods for improving the early-age strength of alkali-activated fly ash(AAFA)binders.This study combined these two approaches by ...Microwave-curing and mechanical grinding of fly ash have both beenadopted as effective methods for improving the early-age strength of alkali-activated fly ash(AAFA)binders.This study combined these two approaches by synthesizing AAFA using original,medium-fine,and ultrafine fly ash as precursors,and then specimens were cured with a five-stage temperature-controlled microwave.The compressive strength results indicate that the original AAFA develops the highest strength initially during microwave-curing,reaching 28 MPa at stage 2.Medium-fine AAFA exhibits the highest strength of 60 MPa when cured to stage 4-I,which is 26%higher than the peak strength of original AAFA.It is attributed to the significant rise in their specific surface area,which accelerates the dissolution of Si and Al from the precursor and facilitates the subsequent formation of N-A-S-H gels.Additionally,nanoscale zeolite crystals formed as secondary products fill the tiny gaps between amorphous products,thereby significantly improving their microstructure.In contrast,ultrafine fly ash,primarily composed of fragmented particles,necessitated a substantial amount of water,which adversely affects the absorption efficiency for microwave of AAFA specimens.Thus,ultrafine AAFA specimens consistently exhibit the lowest compressive strength.Specifically,at the end of curing,the compressive strength of these three specimens with microwave-curing is approximately 32%,59%,and 172%higher than that of the steam-cured sample,respectively.These findings demonstrate the compatibility of microwave-curing and fly ash refinement in enhancing the early compressive strength development of AAFA.展开更多
The main objective of this paper focuses on the changes that occur in the strength and microstructural properties of sodium silicate activated fly ash based geopolymer due to varying the sulfate salt and water content...The main objective of this paper focuses on the changes that occur in the strength and microstructural properties of sodium silicate activated fly ash based geopolymer due to varying the sulfate salt and water content.A series of tests including X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,physical adsorption and unconfined compressive strength were used to investigate this effect.The results indicate that the higher water content has an adverse effect on the alkali activation and microstructural properties of geopolymer,so the optimum mass ratio of sodium sulfate in alkali-activated geopolymer under different water-to-binder ratios shows a“peak shifting”phenomenon,i.e.,the higher the water-to-binder ratio,the higher the optimum mass ratio.Lower presence of sodium sulfate has no significant effect on the alkali-activated geopolymer systems;higher addition of sodium sulfate,however,could cause the symmetrical stretching vibration of Si—O and the symmetrical stretching vibration of Si—O—Si and Al—O—Si,and promote the formation of N-A-S-H gels.Furthermore,the cement effect of the gel and sodium sulfate aggregate could improve the integrity of pore structure obviously.The maximum strength of geopolymer curing at ambient temperature was 52 MPa.This study obtains the rule that the strength properties of alkali-activated geopolymers vary with the water-to-binder ratio and sodium sulfate content.The feasibility of geopolymer co-activated by sodium sulfate and sodium silicate was investigated,and reference for engineering application of alkali-activated geopolymer in salt-bearing areas was provided.展开更多
A novel microwave digestion and alkali fusion assisted hydrothermal method was proposed to synthesize zeolite from coal fly ash and the zeolite product was studied for removal of Cd(II)from aqueous solution through ba...A novel microwave digestion and alkali fusion assisted hydrothermal method was proposed to synthesize zeolite from coal fly ash and the zeolite product was studied for removal of Cd(II)from aqueous solution through batch experiments.The adsorbent was characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,surface area analyzer and zeta potential measurement.The results show that the synthetic zeolite was identified as faujasite.The optimum conditions for removal of Cd(II)are found to be:adsorbent dose of0.5g/L,pH6,contact time of90min and initial concentration of20mg/L,the removal rate of Cd(II)is98.55%.The experimental kinetic data agree well with the pseudo second-order equation;the Langmuir isotherm model is found to be more suitable to explicate the experimental equilibrium isotherm results than Freundlich,Dubinin-Radushkevich and Temkin models,and the maximum adsorption capacity of Cd(II)is found to be86.96mg/g.The thermodynamic parameters such asΔGΘ,ΔHΘandΔSΘwere evaluated and the results show that the adsorption of Cd(II)onto the as-synthesized zeolite is spontaneous,endothermic and feasible under studied conditions.展开更多
Chitosan-coated fly ash(CWF)was prepared by the acid leaching-coating method.Chitosan and fly ash were crosslinked in the solution of acetic acid and sulfuric acid.The microstructure of CWF was conducted by scanning e...Chitosan-coated fly ash(CWF)was prepared by the acid leaching-coating method.Chitosan and fly ash were crosslinked in the solution of acetic acid and sulfuric acid.The microstructure of CWF was conducted by scanning electron microscope(SEM)and X-ray diffraction(XRD).The removal of Cr(VI)from water by CWF was studied by adsorption experiments.The composite prepared by the experiment developed a pore structure and a crystal structure similar to SiO_(2) and chitosan chain-like coating was formed on the surface of fly ash.The new modified material has larger surface roughness,specific surface area and more adsorption channels.The Cr(VI)was enriched in modified materials by electrostatic adsorption between CrO_(4)^(2−)、CrO_(7)^(2−)and-NH_(3)^(+) group and surface acid functional groups.The movement of Cr(VI)in solution is a diffusion process from the main body of the liquid phase to the surface of the liquid film.展开更多
To improve the environmental benefits and solve the problems of large shrinkage and high brittleness, the partial replacement of calcined kaolin by fly ash as a raw material for geopolymer synthesis and the influences...To improve the environmental benefits and solve the problems of large shrinkage and high brittleness, the partial replacement of calcined kaolin by fly ash as a raw material for geopolymer synthesis and the influences of polypropylene (PP) fiber on the mechanical properties and volume stability were investigated. The results show that compressive strength of the geopolymer containing 33.3%(mass fraction) fly ash by steam curing at 80 ℃ for 6 d is improved by 35.5%. The 3-day compressive strength, flexural strength and impacting energy of geopolymers containing 0.05%PP fiber increase by 67.8%, 36.1% and 6.25%, while the shrinkage and modulus of compressibility decrease by 38.6% and 31.3%, respectively. The results of scanning electron microscopy (SEM) and the appearances of crack growths confirm that PP fiber can offer a bridging effect over the harmful pores and defects and change the expanding ways of cracks, resulting in a great improvement of strength and toughness.展开更多
Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data anal...Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.展开更多
A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agen...A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.展开更多
To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration （MSW1） fly ash were studied by measuring the chemica...To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration （MSW1） fly ash were studied by measuring the chemical element composition, specific surface area, pore sizes, functional groups, TEM image, mineralogy and DSC-TG curves of raw and sintered fly ash specimens. The results show that MSWI fly ash particles mostly have irregular shapes and non-typical pore structure, and the supersonic treatment improves the pore structure; MSWI fly ash consists of Such crystals as SiO2, CaSO4 and silica-aluminates, and some soluble salts like KCl and NaCl. During the sintering process, mineralogy changes largely and novel solid solutions are produced gradually with the rise of temperature. Therefore, the utilization of a proper thermal technology not only destructs those persistent organic toxicants but also stabilizes hazardous heavy metals in MSWI fly ash.展开更多
Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatm...Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatment in order to make the glass-ceramics. The crystallization behaviors of the produced glass-ceramics were examined by differential thermal analysis （DTA）, X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Results show that main crystalline phase of the glass-ceramics fi＇om grate fly ash is wollastonite （CaSiO3） with small amount of diopside （Ca（Mg,Al）（Si,Al）206）, and that from fluidized bed fly ash is diopside （Ca（Mg,Al）（Si,Al）206）. It is found that the glass-ceramics sintered at 850 ℃and 1 000℃ from grate fly ash and fluidized bed fly ash respectively have the optimal physical, mechanical and chemical characteristics. Glass-ceramics samples, produced from incinerator fly ash with desirable properties and the low leaching concentration of heavy metals, can be the substitute of nature materials such as marble, granite and porcelain tiles.展开更多
Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast...Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast e from thermal power plant, possess the potential activity of jellification, and can b e used in cemented fill as a partial substitute for cement to reduce the fill co s t. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of f ly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tes ted to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash . The compressive strength of specimens with a ratio of 1∶2∶8 (cement to fly ash to tailings ) can reach 2 MPa after 90 d curing, totally meeting the requiremen t of artificial pillar and reducing the fill cost by 20%-30%.展开更多
The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete （HFC） were investigated. The early-age cracking behavior of the HFC was analyzed by combining the tests of ev...The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete （HFC） were investigated. The early-age cracking behavior of the HFC was analyzed by combining the tests of evaporation capacity and electrical resistivity of the HFC. In these tests, a modified flat-type specimen was adopted. The results show that the HFC will have a lower evaporation capacity when it is mixed with fine fly ash, while it will have a higher evaporation capacity when grade II! fly ash is used as mineral admixture. And the electrical resistivity rate of HFC reduces with the increase of the content of fly ash. A nonlinear relationship exists between the cracking time of HFC and the minimum electrical resistivity. The early-age cracking behavior of HFC with fly ash can be enhanced by appropriately increasing the fine particle content and MgO, K2O, and SO3 contents of fly ash. The optimal content of fly ash, which makes a satisfied early-age cracking behavior of HFC, is obtained. And when the content of fly ash exceeds a critical value, the early-age cracking behavior of HFC will rapidly decrease.展开更多
Washing pre-treatrnent of municipal solid waste incineration （MSWI） fly ash blended with shale and sludge was utilized in the manufacture of light-weight aggregates and processed to form ceramic pellets. A formula u...Washing pre-treatrnent of municipal solid waste incineration （MSWI） fly ash blended with shale and sludge was utilized in the manufacture of light-weight aggregates and processed to form ceramic pellets. A formula uniform design was performed to arrange the mixture ratio of the materials. The optimal mixture ratio of the materials was determined by measuring the bulk density, granule strength, and 1 h water absorption of the pellets. It is shown that the optimal mixture ratios of materials, MSWI fly ash, shale, and sludge, are 23.16%, 62.58%, and 14.25% （mass fraction）, respectively. The performance testing indicators of light-weight aggregates are obtained under the optimum mixture ratio： bulk density of 613 kg/m3, granule strength of 821N, and 1 h water absorption of 11.6%, meeting 700 grade light-aggregate of GB/T 17431.2--1998 standard. The results suggest that utilization of MSWI fly ash in light-weight aggregates is an effective method and a potential means to create much more values.展开更多
文摘Microwave-curing and mechanical grinding of fly ash have both beenadopted as effective methods for improving the early-age strength of alkali-activated fly ash(AAFA)binders.This study combined these two approaches by synthesizing AAFA using original,medium-fine,and ultrafine fly ash as precursors,and then specimens were cured with a five-stage temperature-controlled microwave.The compressive strength results indicate that the original AAFA develops the highest strength initially during microwave-curing,reaching 28 MPa at stage 2.Medium-fine AAFA exhibits the highest strength of 60 MPa when cured to stage 4-I,which is 26%higher than the peak strength of original AAFA.It is attributed to the significant rise in their specific surface area,which accelerates the dissolution of Si and Al from the precursor and facilitates the subsequent formation of N-A-S-H gels.Additionally,nanoscale zeolite crystals formed as secondary products fill the tiny gaps between amorphous products,thereby significantly improving their microstructure.In contrast,ultrafine fly ash,primarily composed of fragmented particles,necessitated a substantial amount of water,which adversely affects the absorption efficiency for microwave of AAFA specimens.Thus,ultrafine AAFA specimens consistently exhibit the lowest compressive strength.Specifically,at the end of curing,the compressive strength of these three specimens with microwave-curing is approximately 32%,59%,and 172%higher than that of the steam-cured sample,respectively.These findings demonstrate the compatibility of microwave-curing and fly ash refinement in enhancing the early compressive strength development of AAFA.
基金Project(51878322)supported by the National Natural Science Foundation of ChinaProject(18YF1FA112)supported by Key Research and Development Program of Gansu Province,China。
文摘The main objective of this paper focuses on the changes that occur in the strength and microstructural properties of sodium silicate activated fly ash based geopolymer due to varying the sulfate salt and water content.A series of tests including X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,physical adsorption and unconfined compressive strength were used to investigate this effect.The results indicate that the higher water content has an adverse effect on the alkali activation and microstructural properties of geopolymer,so the optimum mass ratio of sodium sulfate in alkali-activated geopolymer under different water-to-binder ratios shows a“peak shifting”phenomenon,i.e.,the higher the water-to-binder ratio,the higher the optimum mass ratio.Lower presence of sodium sulfate has no significant effect on the alkali-activated geopolymer systems;higher addition of sodium sulfate,however,could cause the symmetrical stretching vibration of Si—O and the symmetrical stretching vibration of Si—O—Si and Al—O—Si,and promote the formation of N-A-S-H gels.Furthermore,the cement effect of the gel and sodium sulfate aggregate could improve the integrity of pore structure obviously.The maximum strength of geopolymer curing at ambient temperature was 52 MPa.This study obtains the rule that the strength properties of alkali-activated geopolymers vary with the water-to-binder ratio and sodium sulfate content.The feasibility of geopolymer co-activated by sodium sulfate and sodium silicate was investigated,and reference for engineering application of alkali-activated geopolymer in salt-bearing areas was provided.
基金Projects(2013BAC15B01,2013BAB07B03)supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of ChinaProject(Qian Ke He JZ[2014]2009)supported by the Key Foundation of Science and Technology of Guizhou Province,China
文摘A novel microwave digestion and alkali fusion assisted hydrothermal method was proposed to synthesize zeolite from coal fly ash and the zeolite product was studied for removal of Cd(II)from aqueous solution through batch experiments.The adsorbent was characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,surface area analyzer and zeta potential measurement.The results show that the synthetic zeolite was identified as faujasite.The optimum conditions for removal of Cd(II)are found to be:adsorbent dose of0.5g/L,pH6,contact time of90min and initial concentration of20mg/L,the removal rate of Cd(II)is98.55%.The experimental kinetic data agree well with the pseudo second-order equation;the Langmuir isotherm model is found to be more suitable to explicate the experimental equilibrium isotherm results than Freundlich,Dubinin-Radushkevich and Temkin models,and the maximum adsorption capacity of Cd(II)is found to be86.96mg/g.The thermodynamic parameters such asΔGΘ,ΔHΘandΔSΘwere evaluated and the results show that the adsorption of Cd(II)onto the as-synthesized zeolite is spontaneous,endothermic and feasible under studied conditions.
基金Project(41602310)supported by the National Natural Science Foundation of ChinaProject(2017M611044)supported by the China Postdoctoral Science Foundation。
文摘Chitosan-coated fly ash(CWF)was prepared by the acid leaching-coating method.Chitosan and fly ash were crosslinked in the solution of acetic acid and sulfuric acid.The microstructure of CWF was conducted by scanning electron microscope(SEM)and X-ray diffraction(XRD).The removal of Cr(VI)from water by CWF was studied by adsorption experiments.The composite prepared by the experiment developed a pore structure and a crystal structure similar to SiO_(2) and chitosan chain-like coating was formed on the surface of fly ash.The new modified material has larger surface roughness,specific surface area and more adsorption channels.The Cr(VI)was enriched in modified materials by electrostatic adsorption between CrO_(4)^(2−)、CrO_(7)^(2−)and-NH_(3)^(+) group and surface acid functional groups.The movement of Cr(VI)in solution is a diffusion process from the main body of the liquid phase to the surface of the liquid film.
基金Project(2006AA06Z225) supported by the National High-Tech Research and Development Program of China
文摘To improve the environmental benefits and solve the problems of large shrinkage and high brittleness, the partial replacement of calcined kaolin by fly ash as a raw material for geopolymer synthesis and the influences of polypropylene (PP) fiber on the mechanical properties and volume stability were investigated. The results show that compressive strength of the geopolymer containing 33.3%(mass fraction) fly ash by steam curing at 80 ℃ for 6 d is improved by 35.5%. The 3-day compressive strength, flexural strength and impacting energy of geopolymers containing 0.05%PP fiber increase by 67.8%, 36.1% and 6.25%, while the shrinkage and modulus of compressibility decrease by 38.6% and 31.3%, respectively. The results of scanning electron microscopy (SEM) and the appearances of crack growths confirm that PP fiber can offer a bridging effect over the harmful pores and defects and change the expanding ways of cracks, resulting in a great improvement of strength and toughness.
文摘Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.
基金Project(20120023110011) supported by Doctoral Program of Higher Education of ChinaProjects(2009KH09,2009QH02) supported by the Fundamental Research Funds for the Central Universities of China
文摘A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.
基金Project(50808184) supported by the National Natural Science Foundation of China
文摘To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration （MSW1） fly ash were studied by measuring the chemical element composition, specific surface area, pore sizes, functional groups, TEM image, mineralogy and DSC-TG curves of raw and sintered fly ash specimens. The results show that MSWI fly ash particles mostly have irregular shapes and non-typical pore structure, and the supersonic treatment improves the pore structure; MSWI fly ash consists of Such crystals as SiO2, CaSO4 and silica-aluminates, and some soluble salts like KCl and NaCl. During the sintering process, mineralogy changes largely and novel solid solutions are produced gradually with the rise of temperature. Therefore, the utilization of a proper thermal technology not only destructs those persistent organic toxicants but also stabilizes hazardous heavy metals in MSWI fly ash.
基金Project(20806051) supported by the National Natural Science Foundation of ChinaProject(20080440680) supported by China Postdoctoral Science Foundation
文摘Grate fly ash and fluidized bed fly ash mixed with glass cullet additive respectively were melted in the electronic arc-furnace. The product, arc-melting slag, was further treated by crushing, pressing and heat treatment in order to make the glass-ceramics. The crystallization behaviors of the produced glass-ceramics were examined by differential thermal analysis （DTA）, X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Results show that main crystalline phase of the glass-ceramics fi＇om grate fly ash is wollastonite （CaSiO3） with small amount of diopside （Ca（Mg,Al）（Si,Al）206）, and that from fluidized bed fly ash is diopside （Ca（Mg,Al）（Si,Al）206）. It is found that the glass-ceramics sintered at 850 ℃and 1 000℃ from grate fly ash and fluidized bed fly ash respectively have the optimal physical, mechanical and chemical characteristics. Glass-ceramics samples, produced from incinerator fly ash with desirable properties and the low leaching concentration of heavy metals, can be the substitute of nature materials such as marble, granite and porcelain tiles.
文摘Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast e from thermal power plant, possess the potential activity of jellification, and can b e used in cemented fill as a partial substitute for cement to reduce the fill co s t. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of f ly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tes ted to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash . The compressive strength of specimens with a ratio of 1∶2∶8 (cement to fly ash to tailings ) can reach 2 MPa after 90 d curing, totally meeting the requiremen t of artificial pillar and reducing the fill cost by 20%-30%.
基金Project(50478003)supported by the National Natural Science Foundation of ChinaProject(2002F007)supported by the Natural Science Foundation of Fujian Province,China
文摘The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete （HFC） were investigated. The early-age cracking behavior of the HFC was analyzed by combining the tests of evaporation capacity and electrical resistivity of the HFC. In these tests, a modified flat-type specimen was adopted. The results show that the HFC will have a lower evaporation capacity when it is mixed with fine fly ash, while it will have a higher evaporation capacity when grade II! fly ash is used as mineral admixture. And the electrical resistivity rate of HFC reduces with the increase of the content of fly ash. A nonlinear relationship exists between the cracking time of HFC and the minimum electrical resistivity. The early-age cracking behavior of HFC with fly ash can be enhanced by appropriately increasing the fine particle content and MgO, K2O, and SO3 contents of fly ash. The optimal content of fly ash, which makes a satisfied early-age cracking behavior of HFC, is obtained. And when the content of fly ash exceeds a critical value, the early-age cracking behavior of HFC will rapidly decrease.
基金Project(CSTC.2011AC7065) supported by the Science & Technology Committee of Chongqing, China Project(50808184) supported by the National Natural Science Foundation of China
文摘Washing pre-treatrnent of municipal solid waste incineration （MSWI） fly ash blended with shale and sludge was utilized in the manufacture of light-weight aggregates and processed to form ceramic pellets. A formula uniform design was performed to arrange the mixture ratio of the materials. The optimal mixture ratio of the materials was determined by measuring the bulk density, granule strength, and 1 h water absorption of the pellets. It is shown that the optimal mixture ratios of materials, MSWI fly ash, shale, and sludge, are 23.16%, 62.58%, and 14.25% （mass fraction）, respectively. The performance testing indicators of light-weight aggregates are obtained under the optimum mixture ratio： bulk density of 613 kg/m3, granule strength of 821N, and 1 h water absorption of 11.6%, meeting 700 grade light-aggregate of GB/T 17431.2--1998 standard. The results suggest that utilization of MSWI fly ash in light-weight aggregates is an effective method and a potential means to create much more values.
