The reinforced concrete (RC) water retaining tank walls with horizontal construction joints are prone to experiencing seepage under high hydrostatic pressure, which can affect the structural integrity and functionality. To evaluate the impermeability of construction joints with different improvement measures, the permeability test of concrete with and without horizontal construction joints was conducted. The test results show that the addition of Polypropylene fibers (PP fiber) and Cementitious Capillary Crystalline Waterproofing materials (CCCW) can improve the self-waterproofing ability of concrete. The impermeability at the construction joint is much lower than that of single-casting concrete. Moreover, applying CCCW to the water-facing surface of the construction joint can significantly enhance its impermeability. Then, two 1:2 scaled RC tank wall specimens were manufactured, with one wall of conventional concrete and the other wall of modified concrete. The impermeability tests of the typical single-casting and double-layer casting parts of the two wall specimens were carried out respectively. The experimental results show the RC tank wall with construction joint is prone to generate initial defects and seepage, making it difficult to achieve the design watertight requirements. The use of modified concrete materials and surface treatment in the relevant part can effectively improve the impermeability performance of the construction joint. Finally, the BP neural network was used to establish a prediction model between the impermeability of concrete and its material parameters and construction technology.
Recycled concrete with manufactured sand (RCM) is a type of recycled concrete that uses manufactured sand as fine aggregate, and there have been limited reports on the investigation of its high temperature performance in the construction industry. This study, starting from two curing regimes, explored the high temperature performance of RCM with water-to-cementitious ratios of 0.32, 0.4, and 0.48. Various physical properties of the samples in each group were tested, including surface morphology changes, mass loss rate, microstructure and composition alterations, as well as fundamental mechanical properties like compressive strength and elastic moduli. The experimental results indicate that RCM specimens exhibit slightly higher compressive strength after 7 d of high-temperature water curing compared to the 30 d standard curing. Furthermore, following high temperature tests ranging from 200 °C to 800 °C, the strength reduction in the specimens is not significantly pronounced when compared to those subjected to standard curing. Utilizing the measured stress-strain curves and existing constitutive models for high temperature behavior of recycled concrete, this study analyzes the influencing factors affecting the performance of RCM under high temperature conditions. The findings provide theoretical support for the practical engineering application of RCM.
热激励去极化电流(TSDC)测量技术可以提供存在于材料体系中的缺陷类型信息,例如空间电荷、偶极子、陷阱电荷等.通过TSDC谱分析,可研究偶极子和可动离子的性质,以及激活能、弛豫时间、荷电粒子浓度等微观参数,进而更好地理解与缺陷有关的物理本质.本文介绍了当前TSDC技术在无机材料中的应用现状,整理归纳出TSDC技术在线性介质、非线性介质、陶瓷-聚合物复合材料中的研究结果与最新进展,从本质上揭示无机材料中缺陷与性能之间的内在关联.有望拓展TSDC技术在无机材料中的应用,为无机材料微观机制研究提供新思路.
在质子交换膜燃料电池(PEMFC)运行过程中,产生的自由基会攻击质子交换膜,使其开裂或形成孔洞,导致电池失效.常见的改性方法是在质子交换膜(PEM)中添加自由基清除剂材料.基于此,本文合成了Sn掺杂CeO2自由基清除剂,通过提高Ce3+浓度来增强其在PEMFC中自由基清除性能,避免PEM厚度迅速减薄,从而提高质子PEMFC的耐久性.密度泛函理论计算和试验结果表明,Sn掺杂会引起CeO2产生晶格畸变,降低氧空位形成能,促进CeO2中Ce3+的形成.同时,Sn2+的加入可将CeO2-Sn样品中的Ce4+还原为Ce3+,提升Ce3+的浓度,从而提高PEM的耐久性.单电池测试结果表明,经70 h的开路电压衰减测试,CeO2-Sn-5％改性后的质子交换膜组装的单电池电压衰减率最低(18％),且功率保留率(56％)比其他样品更高,表明该样品具有更优异的耐久性.
In order to overcome the disadvantage of poor mechanical properties of composite cementitious material system with large dosage,the response surface method was adopted to optimize the hybrid fiber composite cementitious material system,and the prediction model was established by taking the dosage of steel fiber,polypropylene fiber and desulphurization gypsum as the variable factors,and 28 d flexural strength and compressive strength of cement mortar as the evaluation indexes.Besides,the test of cement mortar and concrete was carried out to verify the predictive model.The results show that when the volume dosage of steel fiber is 0.4% ,the volume dosage of polypropylene fiber is 0.116% and the mass dosage of desulphurization gypsum is 8% ,the working and mechanical properties of composite materials reach the optimum,the predicted values of the 28 d flexural and compressive strength can be up to 7.0 and 37.4 MPa.The relative errors of flexural and compressive strength between the predicted values and the experimental values are only 2.86% and 1.32% and the standard deviation of the test values of flexural strength and compressive strength is 0.148 8 and 1.345 9,proving that the response surface method has high prediction precision,accuracy and scientificity.The optimisation effect of the composite cementitious material system is proved through this study,which provides a new solution idea and test basis for the multi-objective optimisation problem of composite materials.
There are too much iron and alkaline in red mud,which hinders its utilization in cement.In order to enhance the reusing rate of red mud in cement material,this research paid adequate attention on reduction methods for iron recovery from red mud,water heated ion-exchanging methods using calcium carbide slags and oxalic methods for dealkalization of red mud,eventually used refactored red mud after iron recovery and dealkalization to prepare cement clinker.The results show that under the optimized condition that the sintering temperature is 1 400℃ ,lasting time is 1 h,rice husk ash adding content is 9.08% (mass fraction),cooling method is water cooling,the iron recovery rate of red mud is 77.24% while the content of iron declines to 9.39% (mass fraction)after iron recovery.Under the condition that reacting temperature is 90℃ ,deironed red mud and calcium carbide slags mass ratio is 1∶1,liquid to solid rate(mL/g)is 6,reacting time is 7 h,the dealkalizaiton rate of ion exchanging methods using calcium carbide slags is 89.30% ,meanwhile,the content of Na2O in refactored red mud drops to 0.592% (mass fraction),which meets the requirement for cement ingredients that alkaline content must be lower than 1% .When the rate value of cement raw material,namely the lime saturation factor is 0.88,silicon rate factor is 2.4,aluminum rate factor is 1.4,cement raw materials prepared using refactored red mud possess good burnability under the sintering temperature ranging from 1 300℃ to 1 450℃ .When the sintering temperature is 1 350℃ ,grains in cement clinkers show as irregular polygons with normal morphology.Accordingly,the optimum sintering temperature for cement clinker preparation adding refactored red mud is 1 350℃ .
Nano ZrC powder was prepared by salt assisted combustion synthesis process.The effect of raw material ZrO2 particle size on the microstructure of nano ZrC powder and its mechanism were studied.The results show that in ZrO2-Mg-C system,with the decrease of ZrO2 original particle size(200→10 nm),the reaction activity of carbon zirconium system increases and the free carbon content in ZrC decreases gradually.The average particle size of ZrC powder decreases with the decrease of ZrO2 particle size.When ZrO2 with particle size of 10 nm is added,the average particle size of ZrC powder is 48 nm,and the spherical like morphology tends to be more uniform.The particle size of raw material ZrO2 decreases and the specific surface area increases,which improve the reaction activity and carburizing speed,so as to reduce the influences of reaction time and reaction temperature on crystal growth,and obtain high-purity nano ZrC powder with uniform distribution.
The effects of six slag dosages of 0% ,10% ,20% ,30% ,40% and 50% (mass fraction,the same below)on the shrinkage of fly ash-based geopolymer(FAGP)concrete during thermal curing process were studied with digital image correlation(DIC)method.The compressive strength of concrete and paste after thermal curing were tested,and the microscopic mechanism was analyzed by combining simultaneous thermal analysis(TG-DSC),X-ray diffraction(XRD)and scanning electron microscope(SEM).The results show that with the increase of slag content,the total shrinkage and shrinkage rate of FAGP first decrease and then increase,the compressive strength increases first and then decreases,the hydration degree increases,and the number of microcracks increases.When the slag content is 40% ,FAGP concrete has the smallest shrinkage and the highest compressive strength.When the slag content is low,the hydration degree of the geopolymer is small,and there are fewer microcracks.At this time,the main reason for the shrinkage of the geopolymer is the lower elastic modulus at the beginning of thermal curing.When the slag content is high,the hydration degree of the geopolymer is high,and there are many microcracks.At this time,the shrinkage deformation of the geopolymer is mainly caused by a large degree of chemical reaction.
With the proposal of"dual carbon"goal,all kinds of new composite thermal insulation formwork and integrated composite wall have become the current research hotspot.A composite thermal insulation formwork with rigid polyurethane(PUR)insulation board as insulation layer and basalt fiber reinforced polymer(BFRP)composite cement board as surface layer was proposed.Six sets of specimens were designed for push-out shear test.The effects of groove type,depth and number on the interfacial bonding performance between surface layer and insulation layer were studied.The energy dissipation factor was introduced to evaluate the energy dissipation capacity of specimens.The results show that grooving on the insulation board,deepening the grooving depth and increasing the number of grooving can improve the interfacial bonding strength and toughness of the specimen.Comprehensive comparison of various working conditions,grooving on the surface of PUR insulation board can significantly improve the interfacial bonding performance of the specimen.The interfacial bonding performance of the transverse groove specimen is better than that of the longitudinal groove specimen.The"#"-shaped groove specimen makes that the interfacial bonding strength,toughness and energy dissipation capacity of specimen increase by 164% ,286% and 28.57% ,respectively,compared with the unslotted specimen,showing the best interfacial bonding performance.Deepening the grooveing depth has limited improvement on the interfacial bonding performance and has little effect on the energy dissipation capacity.Increasing the number of grooving can improve the interfacial bonding performance of specimen by about 16% .Through regression analysis,the calculation formula of interfacial bonding strength was established,and compared with the experimental results,the calculated values are in good agreement with the experimental values.
To investigate the impact resistance of steel slag fine aggregate concrete,the concrete specimens were prepared by replacing fine aggregate with equal volume of steel slag at replacement rates of 10% ,20% and 30% ,respectively.The impact resistance test was carried out by drop hammer impact device to study the impact life and damage evolution law,and the impact resistance of specimen was compared with ordinary concrete.The results show that the addition of steel slag fine aggregate can improve the impact resistance of concrete,and the impact life is obviously improved when the drop weight is small.There is a certain degree of dispersion in the results of concrete impact resistance test,and the impact life of steel slag concrete conforms to Weibull distribution.Based on the Weibull distribution,the impact life under different failure probabilities is estimated,and the impact damage evolution equation is established to calculate the corresponding impact times when the concrete with different steel slag content reaches a certain damage variable.
The mesoporous SiO2 synthesized by modified Stöber method was used as precursor.The phenolic resin was coated on the surface of SiO2 by self-assembly technology and SiO2@C was formed after carbonization.The mesoporous heterogeneous SiO2@SiC@C microspheres with uniform morphology were obtained by magnesiothermic reaction at 800℃ .As shown in the characterization results of XRD,XPS,Raman,BET,SEM and TEM,the SiO2@SiC@C microspheres were composed of SiC,amorphous SiO2,amorphous C and SiOxCy phases,and a large number of mesoporous structures can be found on the surface.The mesoporous heterogeneous SiO2@SiC@C microspheres exhibit excellent microwave absorption performance in the simulation results of microwave absorption performance.When the simulated matching thickness is 2 mm,the minimum reflection loss reaches-36.83 dB at 17.74 GHz.The maximum absorption bandwidth reaches 6.63 GHz at the simulated matching thickness of 2.5 mm,completely covering the Ku band.The mesoporous heterogeneous SiO2@SiC@C microspheres show strong absorption and wide frequency band.This is the result of the synergistic effect of mesoporous structure optimizing the impedance matching and heterogeneous interface enhancing the interface polarization.The mesoporous heterogeneous SiO2@SiC@C microspheres prepared in this experiment can meet the application requirements in the field of electromagnetic wave absorption protection.
In this study,sodium silicate with varying modulus was synthesized.The influence of sodium silicate modulus on the rheology of kaolin slurry was investigated.Based on the rheological analysis,it has been determined that the kaolin slurry exhibits the lowest shear viscosity when the sodium silicate modulus is 2.5 and the addition amount is 0.33% (mass fraction).Four different models are used to fit the flow curves,and it is found that the Herschel-Bulkley model could obtain the greatest correlation.In addition,the fitting degree is primarily influenced by the shear stress in the low shear rate region,which is mainly affected by the thixotropy of slurry.Then,the thixotropy of slurry with different sodium silicate modulus is characterized by shear hysteresis ring area,which verifies the view above.Finally,the molecular structure of sodium silicate with different modulus was analyzed using infrared spectroscopy.The results indicate the presence of a weak vibration at 589.5 cm-1 in the vibrational spectrum of sodium silicate with a modulus of 2.5,suggesting the presence of distorted 6-membered rings.The annular silicates interact with kaolin particles through Coulombic force,leading to the formation of large aggregates.This interaction prevents the connection between the edges and faces,disrupts the thixotropic structure,and consequently reduces viscosity.This study is helpful to understand the deep reason of the influence of sodium silicate modulus on the mechanism of deflocculation,and provide scientific basis for optimizing the formulation and processing of ceramic slurry.
Magnesium oxysulfate cement has the advantages of light weight,low thermal conductivity and fire resistance,so it has great market potential to be prepared as foamed concrete and applied in building exterior insulation system.The density of ultra-lightweight magnesium oxysulfate foamed concrete was regulated by incorporating high stability modified foam.The changes in pore structure were investigated through scanning electron microscope(SEM)and optical microscope(OM).Additionally,the effects of density and pore structure variations on the compressive strength and thermal conductivity of ultra-lightweight magnesium oxysulfate foamed concrete were also studied.The results indicate that with the increase of content of high stability modified foam,the number of pores increases and the average pore size significantly decreases.The density of ultra-lightweight magnesium oxysulfate foamed concrete decreases gradually,and the compressive strength gradually decreases as well.When the foam content is 250% (mass fraction),the density of ultra-lightweight magnesium oxysulfate foamed concrete reduces to 88.33 kg/m3,and the thermal conductivity reduces to 0.038 2 W/(m·K).
In order to prepare a green inorganic restoration material that is suitable for the restoration of historical buildings,based on the XRD test results of the bonding materials of several historical brick masonry buildings in Qingdao,an artificial hydraulic lime repair mortar was prepared by mixing metakaolin.The influence of metakaolin on the artificial hydraulic lime mortar was studied by testing the fluidity,setting time,mass loss rate,dring shrinkage rate and mechanical properties.The results show that metakaolin can reduce the fluidity,shorten the setting time,reduce the dring shrinkage rate and improve the compressive strength and bonding strength of artificial hydraulic lime mortar.When the content is 5.0% and 7.5% (mass fraction),the 56 d compressive strength of artificial hydraulic lime mortar increases by 66.8% and 94.3% ,and the bond strength increases by 22.2% and 25.9% .Finally,XRD and SEM were used to test and analyze the microstructure of the materials.The results show that the main reason for the improvement of the performance of the artificial hydraulic lime mortar by metakaolin is that the active SiO2 and Al2O3 in metakaolin react directly with the lime,and consume Ca(OH)2,which promotes the hydration of cement and enhances the bonding force between the hydrated products and the aggregate.
Compared with traditional oxy-fuel combustion technology and air combustion technology,the thermochemical regeneration technology of glass furnace has remarkable energy saving effect and is a cutting-edge and disruptive technology for green and low-carbon development of the future high energy consuming glass industry.The thermochemical regeneration technology of glass furnace was experimentally studied by using atmospheric tube furnace and the effects of different experimental conditions on the thermochemical reforming reaction performance of methane/flue gas were analyzed.The results show that methane/flue gas can spontaneously undergo thermochemical reforming at high temperature without catalyst.When the reforming reaction temperature is lower than 900℃ ,the thermochemical reforming reaction of methane/flue gas does not occur.A reaction temperature of 1 200℃ and a reaction time of more than 10 s can ensure the full progress of the reforming reaction.The increase of methane and CO2 content in the reforming reaction gas is conducive to the increase of hydrogen and carbon monoxide yields in the synthesis gas,respectively.
Wind energy is an important clean energy,according to China's carbon peak and carbon neutral strategy,the policy of replacing small with large wind turbine blades and replacing old with new is imperative.The main material of wind turbine blades is glass fiber reinforced polymer,which has problems of difficult recycling technology and high recycling cost.Nowadays,there is no ideal large-scale recycling method.Therefore,the systematic and high-value utilization of waste wind turbine blades is imminent.In this paper,the material type,recycling methods and their respective characteristics of wind turbine blades are summarized.The recent developments of waste wind turbine blades in cement-based materials and thermoplastic polymer materials are thoroughly discussed.Overall,this paper can provide reference for the subsequent development and research on the recycling waste wind turbine blades.
In this paper,gahnite(ZnAl2O4)was prepared with solid phase reaction by ZnO and Al2O3 as raw materials.The micro-structure change of ZnAl2O4 was researched when ZnO/Al2O3 molar ratios were 1.0∶ 0.9,1.0∶ 1.0 and 1.0∶1.1,respectively.In addition,the effect of ZnAl2O4 on properties of high alumina castables were studied.The results show that when the molar ratio of ZnO to Al2O3 is 1.0∶0.9,due to the excessive ZnO,it volatilizes because of the removal of O2-to produce liquid phase,and the surface of ZnAl2O4 particles is microporous structure.When the molar ratio of ZnO and Al2O3 is 1.0∶1.0(standard molar ratio),the surface of ZnAl2O4 particles with standard molar ratio is smooth.The lattice strain value(0.085 86)of standard molar ratio ZnAl2O4 is the smallest,which can capture more manganese ions and iron ions in steel slag.When the molar ratio of ZnO to Al2O3 is 1.0∶1.1,the surface of ZnAl2O4 particles is rough.The high alumina castable with standard molar ratio ZnAl2O4 has denser structure,highest strength and best slag resistance.
For the removal of organic matter in high salinity wastewater,ZSM-5 zeolites with different silicon aluminum molar ratios(Si/Al)were synthesized by hydrothermal method,and were analyzed using XRD,SEM,XRF and BET.The removal effects of zeolites with different silicon aluminum ratios on organic matters in high salinity wastewater were investigated.The temperature of the regeneration of zeolites through calcination were studied also,and the reuse performance of zeolites in the adsorption process of organic matter in high salinity wastewater was evaluated.The results show that with the increase of silicon aluminum ratio of raw material,the particle size of ZSM-5 zeolite gradually decreases,the specific surface area gradually increases,and the adsorption efficiency of zeolite for organic matter in wastewater gradually increases.When silicon aluminum ratio of raw material Si/Al is 500,the synthesized ZSM-5 zeolite has a better adsorption effect on organic matter in wastewater.During 15 times of regeneration and reuse,the removal rate of total organic carbon(TOC)in wastewater is greater than 92.5% .The optimal calcination regeneration temperature of ZSM-5 zeolite is 650℃ .
To study axial compression performance and nonlinear mechanical performance of recycled concrete composite columns with square steel tubes,based on the axial compression performance test of recycled concrete composite columns with square steel tubes,a refined model of composite columns was established by using nonlinear finite element software ABAQUS,and its axial compression performance was analyzed by nonlinear numerical model.On this basis,the effect of recycled aggregate concrete strength grade,tie bar spacing,stirrup spacing,square steel tube wall thickness and slenderness ratio on axial compression performance of composite columns were further expanded and analyzed.The stress strain nephogram and load-displacement curves of composite columns were obtained.The results show that the experimental results are basically consistent with numerical simulation results,which also verifies the rationality of finite element model of composite columns.At the end of loading,the middle part of composite columns is damaged by bulging,which shows that the protective layer of recycled concrete is crushed and falls off,the steel bars and steel tubes are locally bulging,and the core recycled concrete is crushed.With the increase of strength grade of recycled concrete,the bearing capacity and energy dissipation of composite columns gradually increase.Setting tie bars can significantly improve the bearing capacity and energy dissipation of composite columns,but the ductility is only slightly improved.The bearing capacity,ductility and energy dissipation of composite columns decrease with the increase of stirrup spacing and slenderness ratio.With the increase of the wall thickness of square steel tubes,the bearing capacity,deformability and energy dissipation capacity of composite columns are significantly enhanced.
The synergistic preparation of multi-source solid waste binders(MSSWB)using multiple solid wastes is an effective way to utilize solid waste resources.However,the relatively complex raw material composition and low mechanical properties limit the application of MSSWB.100 sets of experimental mix ratios were designed as a data set with the help of D-optimal design method,then PSO-BP was created model for the prediction of the mechanical properties of MSSWB,and the optimal mix ratios of each raw material were determined by particle swarm optimization algorithm(PSO),and finally the hydration products of MSSWB products and the synergistic effect between multiple solid wastes were investigated by microscopic analyses such as XRD,TG-DTG and NMR.The results show that the PSO-BP model can effectively predict the compressive strength of binders,and the mix ratio strength after optimization by the particle swarm optimization algorithm is significantly higher than that of the unoptimized mix ratio strength,the 28 d compressive strength of the cementitious sand in the optimal mix ratio group is 20.8% higher than that of the unoptimized ratio group.The formation of the higher strength in the optimized mix ratio group is mainly related to the higher generation of hydration products of ettringite(AFt)and C-S-H gels.The formation of higher strength in the optimized mix ratio group is mainly related to the higher generation of the hydration products AFt and C-S-H gel and the higher cross-linking degree between the hydration products.This proves that the synergie is even more pronounced when the ratios of the raw materials are optimised.
