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
Residual MgO-CaO brick after being used in AOD furnace was determined by OM, SEM and EDAX. Corrosion mechanism of MgO-CaO brick as furnace lining was studied. Results show that： The corrosion of MgO- CaO brick is mai...Residual MgO-CaO brick after being used in AOD furnace was determined by OM, SEM and EDAX. Corrosion mechanism of MgO-CaO brick as furnace lining was studied. Results show that： The corrosion of MgO- CaO brick is mainly attributed to the solution and infiltration of silicate liquid phase. Transverse cracks between reacted zone and original zone are parallel to the working face, which is an important factor for deteriorating the corrosion of MgO-CaO bricks.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 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
Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to b...Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to basic slags.However,hydration occurs during the manufacturing,storage,and transportation of refractories,which severely limits their application.Mgo-CaO clinker is the main raw material for Mgo-Cao refractories,and its hydration resistance determines the development of the latter case.Herein,the Mgo-Cao clinker was modified using myristic acid as the modifying agent by the liquid-phase deposition method.The effects of the particle size of the raw materials,concentration of myristic acid,treatment temperature and time on the phase composition and hydration resistance of the modified Mgo-Cao clinkers were investigated in detail.The results show that the samples with an agent concentration of 0.25 mol L^(-1) and treated at 25℃ for 1 h exhibit the optimal hydration resistance properties,namely a low hydration mass gain rate(0.23%)and a large water contact angle(152.9).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
This study evaluates the influence of sand content on the mechanical behavior and water resistance of compressed earth bricks(CEBs)manufactured from Lendi clay(Douala,Cameroon).Twenty-seven specimens(prismatic and cub...This study evaluates the influence of sand content on the mechanical behavior and water resistance of compressed earth bricks(CEBs)manufactured from Lendi clay(Douala,Cameroon).Twenty-seven specimens(prismatic and cubic)were produced with three formulations:0%,30%and 60%sand substitution by dry mass,compacted at 2.5 MPa and cured for 7,14 and 28 days.Raw material characterization included particle size distribution,sand equivalent,Atterberg limits,bulk density and Proctor compaction.The clay displayed a liquid limit of 44.07%,plastic limit of 35.23%and plasticity index of 8.84%;optimum moisture content was 15.9%and maximum dry density 1.24 g·cm^(-3).Mechanical testing showed that pure-clay bricks achieved the highest compressive and flexural strengths at all ages(up to≈1.98 MPa and 0.56 MPa respectively).Although the 30%sand mix exhibited marginally higher early compressive strength(7 days),strength decreased substantially by 28 days.Capillary absorption tests revealed an important distinction:while 0%sand bricks exhibited continuous water uptake,they retained cohesion during immersion;conversely,30%and 60%sand bricks disintegrated into a slurry within seconds of immersion,evidencing severe loss of internal bonding.These findings indicate that,for this highly plastic tropical clay,sand acts primarily as a microstructural diluent that undermines long-term cohesion and durability despite short-term packing benefits.The study underscores the need for locally tailored formulations or stabilizers when designing durable CEBs for humid tropical climates.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
This study explores the novel application of Triumfetta pentandra(TP,“Nkui”)fibers,a tropical plant that is abundant yet underutilized in civil engineering,to enhance the performance of compressed earth bricks(CEBs)...This study explores the novel application of Triumfetta pentandra(TP,“Nkui”)fibers,a tropical plant that is abundant yet underutilized in civil engineering,to enhance the performance of compressed earth bricks(CEBs).The main objective is to assess how incorporating these vegetal fibers can improve the mechanical properties of CEBs while maintaining durability.TP fibers were extracted,characterized,and integrated into the soil used for brick specimens.A rigorous experimental protocol was implemented,featuring a unique fiber pre-treatment,the use of a single,homogeneous clayey soil type,and controlled 28-day curing under standard humidity and temperature,which distinguishes this study from previous works.Physical measurements(moisture content,bulk density,water absorption)and mechanical tests(fiber tensile strength,compressive and flexural strength of CEBs)were conducted following French standards.The results indicate that 4%TP fiber content yields optimal mechanical performance,with compressive strength reaching 6.61 MPa and flexural strength 1.49 MPa at 28 days,compared to 5.16 MPa and 0.51 MPa for unreinforced samples.This demonstrates the potential of TP fibers to reinforce earth-based materials,providing a sustainable,locally sourced,and cost-effective construction solution.However,higher fiber content increases porosity and capillary water absorption(up to 16.75 g at 6%fibers),highlighting the importance of optimized fiber dosing and potential complementary treatments for long-term durability.展开更多
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 ℃.
文摘Residual MgO-CaO brick after being used in AOD furnace was determined by OM, SEM and EDAX. Corrosion mechanism of MgO-CaO brick as furnace lining was studied. Results show that： The corrosion of MgO- CaO brick is mainly attributed to the solution and infiltration of silicate liquid phase. Transverse cracks between reacted zone and original zone are parallel to the working face, which is an important factor for deteriorating the corrosion of MgO-CaO bricks.
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 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National Natural Science Foundation of China(Grants 52202025 and U23A20559)Natural Science Foundation of Hubei Province(Grant 2022CFB629)+1 种基金"The 14^(th)Five-Year Plan"Hubei Provincial Advantaged Characteristic Disciplines(Groups)Project of Wuhan University of Science and Technology(2023A0307).
文摘Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to basic slags.However,hydration occurs during the manufacturing,storage,and transportation of refractories,which severely limits their application.Mgo-CaO clinker is the main raw material for Mgo-Cao refractories,and its hydration resistance determines the development of the latter case.Herein,the Mgo-Cao clinker was modified using myristic acid as the modifying agent by the liquid-phase deposition method.The effects of the particle size of the raw materials,concentration of myristic acid,treatment temperature and time on the phase composition and hydration resistance of the modified Mgo-Cao clinkers were investigated in detail.The results show that the samples with an agent concentration of 0.25 mol L^(-1) and treated at 25℃ for 1 h exhibit the optimal hydration resistance properties,namely a low hydration mass gain rate(0.23%)and a large water contact angle(152.9).
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.
文摘This study evaluates the influence of sand content on the mechanical behavior and water resistance of compressed earth bricks(CEBs)manufactured from Lendi clay(Douala,Cameroon).Twenty-seven specimens(prismatic and cubic)were produced with three formulations:0%,30%and 60%sand substitution by dry mass,compacted at 2.5 MPa and cured for 7,14 and 28 days.Raw material characterization included particle size distribution,sand equivalent,Atterberg limits,bulk density and Proctor compaction.The clay displayed a liquid limit of 44.07%,plastic limit of 35.23%and plasticity index of 8.84%;optimum moisture content was 15.9%and maximum dry density 1.24 g·cm^(-3).Mechanical testing showed that pure-clay bricks achieved the highest compressive and flexural strengths at all ages(up to≈1.98 MPa and 0.56 MPa respectively).Although the 30%sand mix exhibited marginally higher early compressive strength(7 days),strength decreased substantially by 28 days.Capillary absorption tests revealed an important distinction:while 0%sand bricks exhibited continuous water uptake,they retained cohesion during immersion;conversely,30%and 60%sand bricks disintegrated into a slurry within seconds of immersion,evidencing severe loss of internal bonding.These findings indicate that,for this highly plastic tropical clay,sand acts primarily as a microstructural diluent that undermines long-term cohesion and durability despite short-term packing benefits.The study underscores the need for locally tailored formulations or stabilizers when designing durable CEBs for humid tropical climates.
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.
文摘This study explores the novel application of Triumfetta pentandra(TP,“Nkui”)fibers,a tropical plant that is abundant yet underutilized in civil engineering,to enhance the performance of compressed earth bricks(CEBs).The main objective is to assess how incorporating these vegetal fibers can improve the mechanical properties of CEBs while maintaining durability.TP fibers were extracted,characterized,and integrated into the soil used for brick specimens.A rigorous experimental protocol was implemented,featuring a unique fiber pre-treatment,the use of a single,homogeneous clayey soil type,and controlled 28-day curing under standard humidity and temperature,which distinguishes this study from previous works.Physical measurements(moisture content,bulk density,water absorption)and mechanical tests(fiber tensile strength,compressive and flexural strength of CEBs)were conducted following French standards.The results indicate that 4%TP fiber content yields optimal mechanical performance,with compressive strength reaching 6.61 MPa and flexural strength 1.49 MPa at 28 days,compared to 5.16 MPa and 0.51 MPa for unreinforced samples.This demonstrates the potential of TP fibers to reinforce earth-based materials,providing a sustainable,locally sourced,and cost-effective construction solution.However,higher fiber content increases porosity and capillary water absorption(up to 16.75 g at 6%fibers),highlighting the importance of optimized fiber dosing and potential complementary treatments for long-term durability.
