Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the ...Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.展开更多
The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that Fe...The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.展开更多
Properties, section structure and service results of recycled MgO-C bricks and new MgO-C bricks for ladle slag line of Baosteel were analyzed and compared, and the measures of improving stability and quality of recycl...Properties, section structure and service results of recycled MgO-C bricks and new MgO-C bricks for ladle slag line of Baosteel were analyzed and compared, and the measures of improving stability and quality of recycled MgO-C bricks were summarized. The results show that： （1） High quality recycled MgO-C materials can be produced by scientific, meticulous and strict management for every process such as dismantling furnace, selection, removing impurity and slag, stacking and homogenization ; （2） Using high quality recycled materials and reasonable production technique, recycled MgO-C bricks with better properties and service efficiency than those of new MgO-C brick can be produced; （3） Service efficiency of recycled MgO - C bricks is good because of its high density, good oxidation resistance and reasonable structure.展开更多
Resins PFG-4 , PFG-8 and a reference resin （resin A） were used as binders of MgO - C bricks, effects of the resins with different molecular structures on wettability of magnesia, on physical properties, mechanical p...Resins PFG-4 , PFG-8 and a reference resin （resin A） were used as binders of MgO - C bricks, effects of the resins with different molecular structures on wettability of magnesia, on physical properties, mechanical properties, oxidation resistance and thermal expansion properties of MgO- C bricks were researched. The results show that the microstructures of solidified resins with different mo- lecular structures are different, which have obvious effect on the cold mechanical properties of MgO - C brick, but little effect on the oxidation resistance, thermal perform- ance and expansion properties.展开更多
The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XR...The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.展开更多
The aim of this study is to enhance the value of local earth materials used in the construction of certain homes in the Republic of Guinea. Thus, a trial study to improve the quality of mud bricks using paper fibers o...The aim of this study is to enhance the value of local earth materials used in the construction of certain homes in the Republic of Guinea. Thus, a trial study to improve the quality of mud bricks using paper fibers obtained by grinding and soaking in water and then drying were used as a stabilizer in the manufacture of these mud bricks from the sample of two sites Dounkiwal (DK) (in Mamou and the sample from the urban commune of Kouroussa). To do this, certain methods and means of identification were carried out, namely: geotechnical, mineralogical and chemical analyses. Sample DK from Mamou has a silty-clay geotechnical characteristic with a plasticity index Ip of 12.75%. However, mineralogical and chemical studies showed that sample Dounkiwal (DK) (Mamou) contains a high proportion of silica and iron oxides (79.63%) and Fe2O3 (11.85%), associated with other alkaline earth oxides and ions: CaO;MgO;SO32−;Cl−, i.e. 3.96%;0.96%;0.28% and 0.039% respectively. Its loss on ignition (LOI) and insoluble residues are 15.40% and 56.36%. The evaluation of the number of huts in Upper and Middle Guinea showed that the populations of these areas have been using mud bricks for several decades in the construction of dwellings. The average value found for the compressive strength of these bricks (from samples I, II and III from Kouroussa) is 0.16 MPa. This value is appreciable in the construction of mud houses.展开更多
This study was part of the framework that contributed not only to the improvement of thermal comfort in housing but also to the decarbonization of the construction and building materials industry. For this purpose, te...This study was part of the framework that contributed not only to the improvement of thermal comfort in housing but also to the decarbonization of the construction and building materials industry. For this purpose, terracotta brick seems to meet these needs. Thus, the objective of this work was to evaluate the influence of the incorporation of coal fly ash from a thermal power plant on the physical and mechanical properties of fired bricks from grey clay in the Thicky area of Senegal. The coal fly ash was incorporated into the raw clay material in proportions of 0, 5, 10, and 15 % by weight. These two raw materials were first characterized by X-ray fluorescence spectroscopy (XRF). The XRF analyses showed that the most abundant oxides in clay were SiO2 (55.034%) and Fe2O3 (10.155%). In coal fly ash, SiO2 (38.574%) is predominant. The ash also contained Al2O3 (7.717%) and alicano-earthy melting oxides such as CaO (9.271%) and MgO (7.298%) etc. These melting oxides were necessary to facilitate the formation of the liquid phase when baking platelets. The latter, when burned at a temperature of 880°C, were characterized by determining the number of physico-mechanical parameters, such as linear shrinkage during cooking, water absorption, fire loss and compressive strength. A Hierarchical Ascending Classification of these different parameters was performed and three classes were obtained. Class 1 with better compressive strength (6.358 MPa), was in sample A (5%). Class 2 consisted of sample D (reference) and had a higher plasticity index (28.51%) and water absorption rate (11.19%). Finally, class 3, which included samples B (10%) and C (15%), had very high shrinkage and fire losses compared to other platelets. These results highlighted the possibility of using up to 5% of the coal fly ash in the production of new fired bricks with good performance.展开更多
This study aims to provide the basic knowledge for furnace refractory design by investigating refractory property changes occurred in a hydrogen atmosphere.Since refractory bricks are thermodynamically stable in a hyd...This study aims to provide the basic knowledge for furnace refractory design by investigating refractory property changes occurred in a hydrogen atmosphere.Since refractory bricks are thermodynamically stable in a hydrogen atmosphere at 1100°C,we tried to find out the minute changes.In this experiment,a refractory brick was prepared by andalusite,mullite chamotte,and clay as raw materials and heated to 1100°C in a 100%hydrogen atmosphere for 72 h.It was found that the strength of the brick was decreased and the color was changed to black by the reduction of impurities.And in addition,this study covered research on the slaking risk of MgO raw materials because the minimum temperature is expected to 400°C in fluidized reduction furnaces unlike shaft furnaces.展开更多
Corrosion effect of ladle furnace （LF） refining slag on fired MgO-CaO bricks with about 34% CaO was studied by static crucible method,and corrosion mechanism was analyzed by techniques of scan electron micrograph,en...Corrosion effect of ladle furnace （LF） refining slag on fired MgO-CaO bricks with about 34% CaO was studied by static crucible method,and corrosion mechanism was analyzed by techniques of scan electron micrograph,energy dispersive spectrometer,and X-ray diffraction. The results show that：MgO-CaO bricks exhibit excellent corrosion resistance but poor penetration resistance to LF refining slag; oxidation of （Mg·Fe）O in reaction zone results in volume expansion forming cracks; penetration of 2CaO·Fe2O3 （C2F） from slag to MgO-CaO bricks increases liquid phases which accelerates corrosion of the bricks; a protective layer of 2CaO·SiO2 formed on reaction interface prevents penetration of C2F to the bricks.展开更多
The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric ...The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric analysis was used to characterize the various stabilizers and the clay used, and tests of resistance and water absorption were also carried out. The clay was found to be an aluminosilicate (15.55% to 17.17% Al2O3 and 42.12% to 44.15% SiO2). The lime contains 90.84% CaO and the cement has 17.80% SiO2, 3.46% Al2O3, 2.43% Fe2O3 and 58.47% CaO in the combined form of tricalcium silicate, dicalcium silicate, tricalcium aluminate and ferro-tetra calcium aluminate. The results showed that the insertion of locally available stabilizers (lime and cement) improved the strength of the material by almost 80% when the lime was increased from 0% to 14% for 14 days. For compressed cement, a 65% increase in strength was observed under the same conditions. Strength increases with drying time, with a 52% increase in strength at 28 days compared to 14 days. Furthermore, compressed cement bricks have a more compact structure, absorbing very little water (32%). In view of all these results, cement appears to be the best stabilizer, and compression improves compressive strength and reduces water absorption.展开更多
The effect of electric fused ZrO2,m-ZrO2 and zirconite on the sintering properties of MgO-CaO bricks was studied and the effect of the ZrO2 content and temperature on BD （bulk density）, AP（apparent porosity）and C...The effect of electric fused ZrO2,m-ZrO2 and zirconite on the sintering properties of MgO-CaO bricks was studied and the effect of the ZrO2 content and temperature on BD （bulk density）, AP（apparent porosity）and CCS （Cold Crushing strength） of MgO-CaO bricks was investigated.The microstructure of burned specimens was analyzed by SEM. The result shows that the sintering property is best while 5% m-ZrO2 was added at 1 600 ℃.展开更多
Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction ...Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction time of 50 min,a reaction layer comprised MgO and CaS with a thickness of 30μm was observed at the interface between the La-free steel and refractory.The MgO layer was observed in La-bearing steel after just 10 min of reaction.The addition of La to the steel accelerated the formation of the MgO layer.As the reaction time increased,a La-containing layer was formed at the La-bearing steel/refractory interface.This La-containing layer progressed through stages from La_(2)O_(2)S+La2O3→La-Ca-O-S→La-Ca-O→La-Ca-Al-O.Furthermore,the evolution of oxide inclusions in the La-free steel followed the sequence of MgO⋅Al_(2)O_(3),Ti-Ca-Al-O and Ti-Mg-Al-O→MgO·Al_(2)O_(3)and MgO with increasing the reaction time.In contrast,the sequence for the La-bearing steel was:La_(2)O_(2)S and La2O3→La_(2)O_(2)S and La-Ti-Al-Mg-O→La-Ti-Al-Mg-O,MgO and MgO·Al_(2)O_(3).The average penetration depth of the La-bearing steel into the refractory was notably lower than that of the La-free steel,revealing that the incorporation of rare earth element La in steel exhibits a significant inhibitory effect on the penetration of molten steel into the MgO-C refractory.展开更多
This study investigated the therapeutic effects on metabolic syndrome(MetS)and the impact on the intestinal barrier and gut microbiota of Fu brick tea aqueous extracts(FTE)on MetS in rats fed with a high-fat diet(HFD)...This study investigated the therapeutic effects on metabolic syndrome(MetS)and the impact on the intestinal barrier and gut microbiota of Fu brick tea aqueous extracts(FTE)on MetS in rats fed with a high-fat diet(HFD).Here,the results showed that FTE supplement significantly reduced HFD-induced weight gain,adiposity,dyslipidemia,fasting blood glucose(FBG)increment,and non-alcoholic fatty liver disease(NAFLD).Moreover,FTE supplement resulted in a decline in lipopolysaccharide(LPS)level and attenuation of colonic inflammation and oxidative stress to protect the intestinal barrier function.FTE supplement also maintained the intestinal barrier integrity by improving histological appearance and promoting ZO-1,Occludin,and Claudin-1 protein expression levels.Meanwhile,FTE supplement alleviated the gut microbiota dysbiosis by enhancing the Firmicutes/Bacteroidetes(F/B)ratio and stimulating the colonization of probiotic bacteria such as Akkermansia,Lactobacillus,Adlercreutzia,and Bacteroides.These findings collectively suggest that Fu brick tea could alleviate MetS and MetS-associated traits with the mechanism relevant to the protection of intestinal barrier and gut microbiota regulation.展开更多
With brick-wall solar greenhouses in Changli area as the research object,using temperature dynamic monitoring and statistical methods,the greenhouse structure suitable for promoting early cultivation of local peach tr...With brick-wall solar greenhouses in Changli area as the research object,using temperature dynamic monitoring and statistical methods,the greenhouse structure suitable for promoting early cultivation of local peach trees was selected by studying the temperature data of the solar greenhouses during the winter solstice,and a prediction model for daily average temperature was constructed.The results showed that greenhouse Ⅰ had reasonable structural parameters and good daylight during the day.However,due to the low wall thickness and poor insulation material,the minimum temperature was significantly lower than other greenhouses.The thermal insulation performance of greenhouse Ⅱ and Ⅲ was better than that of greenhouse Ⅰ,but the depth-span ratio and the front roof lighting angle were smaller.During the winter solstice,the average temperature of the three greenhouses was between 10 and 15℃,which was suitable for early cultivation of peach trees.The prediction model of daily average temperature was obtained:Daily average temperature=1.02+0.69×Daily average temperature of the previous day+0.02×Maximum temperature of the previous day-0.01×Minimum temperature of the previous day.To sum up,the structural parameters of brick-wall solar greenhouses suitable for early cultivation of peach trees in Changli area were as follows:span 6.5-8.5 m,depth-span ratio 0.47,front roof lighting angle 30°and wall thickness greater than 55 cm.展开更多
In order to improve the efficient and high-value recycling utilization rate of waste red bricks from construction waste,this study crushed and ground the waste red bricks to produce recycled brick powder(RBP)with diff...In order to improve the efficient and high-value recycling utilization rate of waste red bricks from construction waste,this study crushed and ground the waste red bricks to produce recycled brick powder(RBP)with different fineness,used the Andreasen model to explore the influence of RBP on the compact filling effect of cementitious material system based on the basic characteristics of RBP.The influence of grinding time(10,20,30 min)and content(0%,5%,10%,15%,20%)of RBP on the macroscopic mechanical properties of cementitious materials was investigated.We analyzed the significant impact of RBP particle characteristics on the compressive strength of the specimen with the aid of grey entropy theory,and revealed the influence mechanism of RBP on the microstructure of cementitious materials by scanning electron microscope(SEM)and nuclear magnetic resonance(NMR).The results show that the fineness of RBP after grinding is smaller than that of cement.The fineness of recycled brick powder increases gradually with the extension of grinding time,which is manifested as the increase of<3μm particles and the decrease of>18μm particles.Compared with the unitary cement cementitious material system,the particle gradation of the RBP-cement binary cementitious material system is closer to the closest packing state.With the increase of RBP content and grinding time,the compactness of the binary cementitious system gradually decreases,indicating that the incorporation of RBP reduces the mechanical strength of the specimen.The results of grey entropy show that the specific surface area D(0.1)and<45μm particles are the significant factors affecting the mechanical properties of cementitious materials mixed with RBP.RBP mainly affects the macroscopic properties of cementitious materials by affecting the internal compactness,the number of hydration products and the pore structure.The results of SEM show that when the RBP content is less than 15%,the content of C-S-H in cement paste increase,and the content of Ca(OH)2 decreases,and the content of C-S-H decreases and the content of Ca(OH)2 increases when the RBP content is more than 15%.The NMR results show that with the extension of grinding time,the pore size of micropore increases gradually,that of middle-small pores decreases gradually,and that of large pores remains unchanged.With the increase of RBP content,the micropores first decrease and then increase,and the middle-small pores and large pores gradually decrease.In summary,the compactness of cementitious material system can be improved by adjusting the fineness of RBP.Considering the performance of cementitious materials and the utilization rate of RBP,it is recommended that the grinding time of RBP is 20 min and the content is 10%-15%.展开更多
In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression condit...In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.展开更多
Nitrogen gas pressure sintering was successfully employed to achieve the in-situ formation of Si_(3)N_(4)-bonded MgO-C refractories.The primary objective was to investigate the influence of different gas pressures on ...Nitrogen gas pressure sintering was successfully employed to achieve the in-situ formation of Si_(3)N_(4)-bonded MgO-C refractories.The primary objective was to investigate the influence of different gas pressures on the mechanical properties and microstructure of MgO-C refractories.The results indicate that higher nitrogen pressure promotes the transformation of silicon nitride from theαphase to theβphase.This phase transition positively impacts the mechanical properties of Si_(3)N_(4)-bonded MgO-C refractories,leading to an enhancement in their overall strength.Notably,when the nitrogen pressure was set at 3 MPa,exceptional compressive strength of 109.7 MPa and an elastic modulus of 142.4 GPa were achieved by these prepared refractories.These findings highlight the great potential for utilizing gas pressure sintered Si_(3)N_(4)-MgO-C refractories.展开更多
基金Enterprise Research and Development Project of Beijing Lirr High-Temperature Materials Co.,Ltd.(2020-02)Key Scientific Research Project for Universities and Colleges in Henan Province(19A430028)+1 种基金the Excellent Youth Research Project of Anhui Province(2022AH030135)the PhD Research Funding of Suzhou University(2021BSK041).
文摘Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.
基金Item Sponsored by National Natural Science Foundation of China (51090382)
文摘The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.
文摘Properties, section structure and service results of recycled MgO-C bricks and new MgO-C bricks for ladle slag line of Baosteel were analyzed and compared, and the measures of improving stability and quality of recycled MgO-C bricks were summarized. The results show that： （1） High quality recycled MgO-C materials can be produced by scientific, meticulous and strict management for every process such as dismantling furnace, selection, removing impurity and slag, stacking and homogenization ; （2） Using high quality recycled materials and reasonable production technique, recycled MgO-C bricks with better properties and service efficiency than those of new MgO-C brick can be produced; （3） Service efficiency of recycled MgO - C bricks is good because of its high density, good oxidation resistance and reasonable structure.
文摘Resins PFG-4 , PFG-8 and a reference resin （resin A） were used as binders of MgO - C bricks, effects of the resins with different molecular structures on wettability of magnesia, on physical properties, mechanical properties, oxidation resistance and thermal expansion properties of MgO- C bricks were researched. The results show that the microstructures of solidified resins with different mo- lecular structures are different, which have obvious effect on the cold mechanical properties of MgO - C brick, but little effect on the oxidation resistance, thermal perform- ance and expansion properties.
文摘The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.
文摘The aim of this study is to enhance the value of local earth materials used in the construction of certain homes in the Republic of Guinea. Thus, a trial study to improve the quality of mud bricks using paper fibers obtained by grinding and soaking in water and then drying were used as a stabilizer in the manufacture of these mud bricks from the sample of two sites Dounkiwal (DK) (in Mamou and the sample from the urban commune of Kouroussa). To do this, certain methods and means of identification were carried out, namely: geotechnical, mineralogical and chemical analyses. Sample DK from Mamou has a silty-clay geotechnical characteristic with a plasticity index Ip of 12.75%. However, mineralogical and chemical studies showed that sample Dounkiwal (DK) (Mamou) contains a high proportion of silica and iron oxides (79.63%) and Fe2O3 (11.85%), associated with other alkaline earth oxides and ions: CaO;MgO;SO32−;Cl−, i.e. 3.96%;0.96%;0.28% and 0.039% respectively. Its loss on ignition (LOI) and insoluble residues are 15.40% and 56.36%. The evaluation of the number of huts in Upper and Middle Guinea showed that the populations of these areas have been using mud bricks for several decades in the construction of dwellings. The average value found for the compressive strength of these bricks (from samples I, II and III from Kouroussa) is 0.16 MPa. This value is appreciable in the construction of mud houses.
文摘This study was part of the framework that contributed not only to the improvement of thermal comfort in housing but also to the decarbonization of the construction and building materials industry. For this purpose, terracotta brick seems to meet these needs. Thus, the objective of this work was to evaluate the influence of the incorporation of coal fly ash from a thermal power plant on the physical and mechanical properties of fired bricks from grey clay in the Thicky area of Senegal. The coal fly ash was incorporated into the raw clay material in proportions of 0, 5, 10, and 15 % by weight. These two raw materials were first characterized by X-ray fluorescence spectroscopy (XRF). The XRF analyses showed that the most abundant oxides in clay were SiO2 (55.034%) and Fe2O3 (10.155%). In coal fly ash, SiO2 (38.574%) is predominant. The ash also contained Al2O3 (7.717%) and alicano-earthy melting oxides such as CaO (9.271%) and MgO (7.298%) etc. These melting oxides were necessary to facilitate the formation of the liquid phase when baking platelets. The latter, when burned at a temperature of 880°C, were characterized by determining the number of physico-mechanical parameters, such as linear shrinkage during cooking, water absorption, fire loss and compressive strength. A Hierarchical Ascending Classification of these different parameters was performed and three classes were obtained. Class 1 with better compressive strength (6.358 MPa), was in sample A (5%). Class 2 consisted of sample D (reference) and had a higher plasticity index (28.51%) and water absorption rate (11.19%). Finally, class 3, which included samples B (10%) and C (15%), had very high shrinkage and fire losses compared to other platelets. These results highlighted the possibility of using up to 5% of the coal fly ash in the production of new fired bricks with good performance.
基金supported by the Korea Planning & Evaluation Institute of Industrial Technology (KEIT)the Ministry of Trade, Industry & Energy (MOTIE, Korea) of the Republic of Korea (No. RS2023-00262421)
文摘This study aims to provide the basic knowledge for furnace refractory design by investigating refractory property changes occurred in a hydrogen atmosphere.Since refractory bricks are thermodynamically stable in a hydrogen atmosphere at 1100°C,we tried to find out the minute changes.In this experiment,a refractory brick was prepared by andalusite,mullite chamotte,and clay as raw materials and heated to 1100°C in a 100%hydrogen atmosphere for 72 h.It was found that the strength of the brick was decreased and the color was changed to black by the reduction of impurities.And in addition,this study covered research on the slaking risk of MgO raw materials because the minimum temperature is expected to 400°C in fluidized reduction furnaces unlike shaft furnaces.
文摘Corrosion effect of ladle furnace （LF） refining slag on fired MgO-CaO bricks with about 34% CaO was studied by static crucible method,and corrosion mechanism was analyzed by techniques of scan electron micrograph,energy dispersive spectrometer,and X-ray diffraction. The results show that：MgO-CaO bricks exhibit excellent corrosion resistance but poor penetration resistance to LF refining slag; oxidation of （Mg·Fe）O in reaction zone results in volume expansion forming cracks; penetration of 2CaO·Fe2O3 （C2F） from slag to MgO-CaO bricks increases liquid phases which accelerates corrosion of the bricks; a protective layer of 2CaO·SiO2 formed on reaction interface prevents penetration of C2F to the bricks.
文摘The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric analysis was used to characterize the various stabilizers and the clay used, and tests of resistance and water absorption were also carried out. The clay was found to be an aluminosilicate (15.55% to 17.17% Al2O3 and 42.12% to 44.15% SiO2). The lime contains 90.84% CaO and the cement has 17.80% SiO2, 3.46% Al2O3, 2.43% Fe2O3 and 58.47% CaO in the combined form of tricalcium silicate, dicalcium silicate, tricalcium aluminate and ferro-tetra calcium aluminate. The results showed that the insertion of locally available stabilizers (lime and cement) improved the strength of the material by almost 80% when the lime was increased from 0% to 14% for 14 days. For compressed cement, a 65% increase in strength was observed under the same conditions. Strength increases with drying time, with a 52% increase in strength at 28 days compared to 14 days. Furthermore, compressed cement bricks have a more compact structure, absorbing very little water (32%). In view of all these results, cement appears to be the best stabilizer, and compression improves compressive strength and reduces water absorption.
文摘The effect of electric fused ZrO2,m-ZrO2 and zirconite on the sintering properties of MgO-CaO bricks was studied and the effect of the ZrO2 content and temperature on BD （bulk density）, AP（apparent porosity）and CCS （Cold Crushing strength） of MgO-CaO bricks was investigated.The microstructure of burned specimens was analyzed by SEM. The result shows that the sintering property is best while 5% m-ZrO2 was added at 1 600 ℃.
基金the support from the National Key R&D Program(No.2023YFB3709900)the National Key R&D Program(No.2023YFB3709901)+2 种基金the National Natural Science Foundation of China(Grant No.U22A20171)the Hebei Natural Science Foundation(Grant No.52304340)the High Steel Center(HSC)at North China University of Technology.
文摘Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction time of 50 min,a reaction layer comprised MgO and CaS with a thickness of 30μm was observed at the interface between the La-free steel and refractory.The MgO layer was observed in La-bearing steel after just 10 min of reaction.The addition of La to the steel accelerated the formation of the MgO layer.As the reaction time increased,a La-containing layer was formed at the La-bearing steel/refractory interface.This La-containing layer progressed through stages from La_(2)O_(2)S+La2O3→La-Ca-O-S→La-Ca-O→La-Ca-Al-O.Furthermore,the evolution of oxide inclusions in the La-free steel followed the sequence of MgO⋅Al_(2)O_(3),Ti-Ca-Al-O and Ti-Mg-Al-O→MgO·Al_(2)O_(3)and MgO with increasing the reaction time.In contrast,the sequence for the La-bearing steel was:La_(2)O_(2)S and La2O3→La_(2)O_(2)S and La-Ti-Al-Mg-O→La-Ti-Al-Mg-O,MgO and MgO·Al_(2)O_(3).The average penetration depth of the La-bearing steel into the refractory was notably lower than that of the La-free steel,revealing that the incorporation of rare earth element La in steel exhibits a significant inhibitory effect on the penetration of molten steel into the MgO-C refractory.
基金supported by the Earmarked Fund for the Modern Agricultural Industry Technology System(CARS19),Research on Quality Chemical Characteristics and Healthy Function of Xianyang Brick Tea(2021kjc-js231)Research on Metabolite Alteration and Mechanism in Fu Brick Tea under the Action of Eurotium cristatum(31471706).
文摘This study investigated the therapeutic effects on metabolic syndrome(MetS)and the impact on the intestinal barrier and gut microbiota of Fu brick tea aqueous extracts(FTE)on MetS in rats fed with a high-fat diet(HFD).Here,the results showed that FTE supplement significantly reduced HFD-induced weight gain,adiposity,dyslipidemia,fasting blood glucose(FBG)increment,and non-alcoholic fatty liver disease(NAFLD).Moreover,FTE supplement resulted in a decline in lipopolysaccharide(LPS)level and attenuation of colonic inflammation and oxidative stress to protect the intestinal barrier function.FTE supplement also maintained the intestinal barrier integrity by improving histological appearance and promoting ZO-1,Occludin,and Claudin-1 protein expression levels.Meanwhile,FTE supplement alleviated the gut microbiota dysbiosis by enhancing the Firmicutes/Bacteroidetes(F/B)ratio and stimulating the colonization of probiotic bacteria such as Akkermansia,Lactobacillus,Adlercreutzia,and Bacteroides.These findings collectively suggest that Fu brick tea could alleviate MetS and MetS-associated traits with the mechanism relevant to the protection of intestinal barrier and gut microbiota regulation.
基金Supported by Modern Agricultural Industry Technology System Innovation Team Construction in Hebei Province(HBCT2023130404).
文摘With brick-wall solar greenhouses in Changli area as the research object,using temperature dynamic monitoring and statistical methods,the greenhouse structure suitable for promoting early cultivation of local peach trees was selected by studying the temperature data of the solar greenhouses during the winter solstice,and a prediction model for daily average temperature was constructed.The results showed that greenhouse Ⅰ had reasonable structural parameters and good daylight during the day.However,due to the low wall thickness and poor insulation material,the minimum temperature was significantly lower than other greenhouses.The thermal insulation performance of greenhouse Ⅱ and Ⅲ was better than that of greenhouse Ⅰ,but the depth-span ratio and the front roof lighting angle were smaller.During the winter solstice,the average temperature of the three greenhouses was between 10 and 15℃,which was suitable for early cultivation of peach trees.The prediction model of daily average temperature was obtained:Daily average temperature=1.02+0.69×Daily average temperature of the previous day+0.02×Maximum temperature of the previous day-0.01×Minimum temperature of the previous day.To sum up,the structural parameters of brick-wall solar greenhouses suitable for early cultivation of peach trees in Changli area were as follows:span 6.5-8.5 m,depth-span ratio 0.47,front roof lighting angle 30°and wall thickness greater than 55 cm.
基金Funded by National Natural Science Foundation of China(No.52108219)Lanzhou University of Technology Hongliu Outstanding Young Talent Program,China(No.062407)The High Quality of Green Machine-made Aggregate and the Evolution Mechanism of Concrete Life Cycle Performance in the Harsh Environment of Northwest China(No.U21A20150)。
文摘In order to improve the efficient and high-value recycling utilization rate of waste red bricks from construction waste,this study crushed and ground the waste red bricks to produce recycled brick powder(RBP)with different fineness,used the Andreasen model to explore the influence of RBP on the compact filling effect of cementitious material system based on the basic characteristics of RBP.The influence of grinding time(10,20,30 min)and content(0%,5%,10%,15%,20%)of RBP on the macroscopic mechanical properties of cementitious materials was investigated.We analyzed the significant impact of RBP particle characteristics on the compressive strength of the specimen with the aid of grey entropy theory,and revealed the influence mechanism of RBP on the microstructure of cementitious materials by scanning electron microscope(SEM)and nuclear magnetic resonance(NMR).The results show that the fineness of RBP after grinding is smaller than that of cement.The fineness of recycled brick powder increases gradually with the extension of grinding time,which is manifested as the increase of<3μm particles and the decrease of>18μm particles.Compared with the unitary cement cementitious material system,the particle gradation of the RBP-cement binary cementitious material system is closer to the closest packing state.With the increase of RBP content and grinding time,the compactness of the binary cementitious system gradually decreases,indicating that the incorporation of RBP reduces the mechanical strength of the specimen.The results of grey entropy show that the specific surface area D(0.1)and<45μm particles are the significant factors affecting the mechanical properties of cementitious materials mixed with RBP.RBP mainly affects the macroscopic properties of cementitious materials by affecting the internal compactness,the number of hydration products and the pore structure.The results of SEM show that when the RBP content is less than 15%,the content of C-S-H in cement paste increase,and the content of Ca(OH)2 decreases,and the content of C-S-H decreases and the content of Ca(OH)2 increases when the RBP content is more than 15%.The NMR results show that with the extension of grinding time,the pore size of micropore increases gradually,that of middle-small pores decreases gradually,and that of large pores remains unchanged.With the increase of RBP content,the micropores first decrease and then increase,and the middle-small pores and large pores gradually decrease.In summary,the compactness of cementitious material system can be improved by adjusting the fineness of RBP.Considering the performance of cementitious materials and the utilization rate of RBP,it is recommended that the grinding time of RBP is 20 min and the content is 10%-15%.
基金Funded by the Project of National Key Research and Development Program of China(No.2019YFC1906202)。
文摘In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.
基金the financial support from the National Natural Science Foundation of China(U21A2057 and 52402034)the Key Research and Development Program of Hubei Province(2023BAB106).
文摘Nitrogen gas pressure sintering was successfully employed to achieve the in-situ formation of Si_(3)N_(4)-bonded MgO-C refractories.The primary objective was to investigate the influence of different gas pressures on the mechanical properties and microstructure of MgO-C refractories.The results indicate that higher nitrogen pressure promotes the transformation of silicon nitride from theαphase to theβphase.This phase transition positively impacts the mechanical properties of Si_(3)N_(4)-bonded MgO-C refractories,leading to an enhancement in their overall strength.Notably,when the nitrogen pressure was set at 3 MPa,exceptional compressive strength of 109.7 MPa and an elastic modulus of 142.4 GPa were achieved by these prepared refractories.These findings highlight the great potential for utilizing gas pressure sintered Si_(3)N_(4)-MgO-C refractories.
