Table of Content

15 January 2024, Volume 43 Issue 1

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Cement and Concrete

Research Progress on Life Prediction of Cracked Concrete under Environment and Fatigue Load

SI Xiuyong, GAO Qingyu, PAN Huimin, ZHAO Qingxin

2024, 43(1):  1-15. 

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Concrete is a quasi brittle material, and a large number of concrete structures inevitably experience cracks and work with them during their designed service life. The existence of cracks directly affects the service life of concrete structures, especially under erosion environmental factors or fatigue loads. The crack propagation process of reinforced concrete is analyzed. The deterioration mechanism, life prediction methods and prediction models of cracked concrete structures under different erosion environments are systematically reviewed and compared. The application status and advantages of fatigue crack propagation theory in fatigue life prediction of cracked concrete structures are described, and some life prediction methods and prediction models based on this theory are summarized. In addition, the life prediction methods of cracked concrete structures under the coupling action of erosion environment and fatigue load are summarized and discussed. In the end, the existing problems in the field of life prediction of cracked concrete structures are pointed out and some suggestions for future research are put forward.

Mechanical Properties of Calcium Carbonate Whisker Hybrid Polyethylene Fiber Reinforced Cement-Based Composite

CHEN Yueshun, TANG Chengyu

2024, 43(1):  16-26. 

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In order to study the influence of calcium carbonate whisker with different content on the mechanical properties and microstructure of polyethylene fiber reinforced cement-based composite(PE-ECC), four groups of PE-ECC specimens with different content of calcium carbonate whisker were designed, and the compressive properties, tensile properties and three-point bending fracture properties were tested on them. The microstructure was studied by XRD, SEM and NMR. The results show that calcium carbonate whisker can strengthen and toughen PE-ECC. With the increase of calcium carbonate whisker content, the strengthening and toughening effects first increase and then decrease. When the content of calcium carbonate whisker is 1% (volume fraction), the compressive properties, tensile properties and fracture properties of PE-ECC are improved best. Appropriate amount of calcium carbonate whisker can fill the matrix, reduce the number of less and more damaged pores, and improve pore structure.

Rheological Characteristics of Thickened Slurry for Preventing and Controlling Spontaneous Combustion of Coal in Underhand Working Face

ZHU Licheng, SHI Zhengjing, FANG Xiuzheng, LU Yi, WU Xiaoying, GUO Xin, XING Shunbo

2024, 43(1):  27-34. 

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In response to the problems of difficulty in grouting, high air leakage intensity, and inability to pile up slurry at high altitudes during the prevention and control process of coal spontaneous combustion in steep dip underhand working face, a slurry with different water to soil ratios and thickening agent concentrations was prepared using polymer material, surfactant, and solid phase materials as raw materials, and suspension stability experiments were conducted to study the suspension characteristics of thickened slurry. By conducting rheological characteristic tests on thickened slurry of different concentrations and fitting the rheological constitutive equation, a thickened slurry material with excellent performance and suitable for steep dip underhand working face was developed. Finally, Fluent software was used to simulate the diffusion characteristics of thickened slurry in the goaf. The research results indicate that loess is the most suitable solid phase material for thickened slurry. When the water to soil mass ratio is 8∶1 and the mass fraction of thickening agent is 0.3%, the suspension performance of thickened slurry is good, and its yield stress is the smallest, indicating better flowability. The flow velocity of thickened slurry in the goaf is inversely proportional to the diffusion radius, and the diffusion radius reaches its maximum value after 6 h of slurry injection.

Pore Structure Evolution of Limestone Powder Hardened Cement Slurry Based on Electrochemical Impedance Spectroscopy

ZHU Pengfei, YU Yi, SHI Yanran, YANG Heng, HE Yang, XU Fei, JIANG Linhua, CHU Hongqiang, XU Tianlei, XU Ning

2024, 43(1):  35-43. 

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In order to study the pore structure evolution behavior of the hardened cement slurry with high-dosage (mass fraction above 20%) limestone powder, based on electrochemical impedance spectroscopy (EIS) and mercury porosimetry (MIP) test analysis, the influence of high-dosage limestone powder on the EIS topological structure and pore structure parameters of the hardened cement slurry were explored. The microstructural equivalent circuit of hardened cement slurry with high-dosage limestone powder was established, and the relationship between components in the equivalent circuit and pore structure parameters was studied. The results show that the effect of limestone powder content on the EIS topological parameters of Bode angle and θ_max is significant with the increase of hydration age, and the pore size distribution of the hardened cement slurry with high-dosage limestone powder content is roughly evolved from large pores and capillary pores to transition pores and gel pores. In addition, the resistance of EIS equivalent circuit decreases with the increase of capillary pore content in hardened cement slurry, and the capacitance decreases with the increase of gel pore content in hardened cement slurry.

Decontamination and Hydration Performance of Photocatalytic Mortar Loaded with S-g-C₃N₄/MgAl-CLDH

LIN Shujin, LUO Shengyang, XIONG Xiaoli

2024, 43(1):  44-51. 

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In this study, a new type of photocatalytic composite material “sulfur-doped carbon nitride/calcined magnesium aluminum hydrotalcite (S-g-C₃N₄/MgAl-CLDH)” was synthesized and loaded on cement mortar through internal doping. The nitrogen oxide (NO_x) degradation and hydration performance of photocatalytic mortar were tested. The results show that when the photocatalyst dosage is less than 5% (mass fraction), the S-g-C₃N₄/MgAl-CLDH content is directly proportional to the NO_x degradation rate of mortar. When the photocatalyst dosage exceeds 5%, the NO_x degradation performance of mortar begins to decrease due to agglomeration. In addition, due to the nucleation effect of nanomaterials, the incorporation of an appropriate amount of S-g-C₃N₄/MgAl-CLDH significantly improves the early (1 d) hydration degree of cement. However, due to its water absorption and agglomeration phenomenon, excess S-g-C₃N₄/MgAl-CLDH reduces the later hydration degree of cement. When the photocatalyst dosage is 7%, the 28 d strength of cement mortar significantly decreases compared with the control mortar. In addition, an appropriate amount of S-g-C₃N₄/MgAl-CLDH (3%) can improve 28 d strength of mortar due to its micro-filling effect.

Synthesis and Properties of Water-Reducing and Slump-Protecting Polycarboxylate Superplasticizer

DONG Jiantong, LIU Zhiyong, HU Zhongshuai, ZHU Dandan, DING Yi, ZHANG Weiqiang, LAI Fukun

2024, 43(1):  52-60. 

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The water-reducing and slump-protecting polycarboxylate superplasticizer (V-HEA) was prepared by free-radical polymerization with 4-hydroxybutyl vinyl polyoxyethylene ether (VPEG) macromonomer and acrylic acid (AA) as the main raw materials by adding the slump-preserving monomer hydroxyethyl acrylate (HEA), and mercapto-propionic acid (MPA) as chain transferr agent under the H₂O₂/L-vitamin C (V_C) oxidation-reductioninitiator system. The synthesized V-HEA was characterized by infrared spectroscopy, gel chromatography testing, and it was subjected to hydration heat analysis and concrete performance comparison analysis with commercially available slump-preserving polycarboxylate superplasticizer (HPWR-S). The results show that the optimal synthesis process parameters of V-HEA are acid-ether ratio of 4.4, ester-ether ratio of 2.5, and the dosage of initiator, ferrous sulfate and chain transfer agent accounted for 0.76%, 0.10% and 0.74% of the mass of the macromonomer, respectively. The incorporation of ferrous sulfate could improve the conversion rate of monomers, and the number average molecular weight of V-HEA is 17 650, the weight average molecular weight is 42 713, and the conversion rate of monomers is as high as 95.03%. The peak temperature of hydration reaches by the incorporation of V-HEA is delayed by 4 h 24 min compared with HPWR-S, and the occurrence time of the second hydration rate peak is delayed by about 4 h, which further delays the hydration of cement. In comparison test of concrete performance, the 2 h slump only decreases by 5.8% with the addition of V-HEA, and the strength of concrete is comparable to that of HPWR-S products, so V-HEA has good application prospects.

Adaptation and Strength Enhancement Mechanisms of Liquid Accelerators in Low Temperature

DU Shuang, WANG Wei, QIAO Min, ZENG Luping, ZHAO Shuang, CHEN Junsong, WU Qingyong, ZHU Bosong

2024, 43(1):  61-70. 

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Accelerators are generally applied in shotcrete to achieve rapid setting and hardening of the concrete. Alkaline and alkali-free liquid accelerators were investigated for their setting-promoting mechanism and strength enhancement at 20 and 5 ℃, and the effect of different types of accelerators on the hydration process and setting-promoting mechanism of cement were analyzed by using heat of hydration analysis, XRD, TG and SEM. The results show that when alkali-free liquid accelerators content of 8% (mass fraction, the same below), alkaline liquid accelerators content of 5% the requirements of the initial setting time not more than 5 min, the final setting time not more than 12 min were met. The environment 5 ℃ will delay final setting time of the slurry and reduce early strength of the mortar mixed with accelerator. Alkali-free accelerator still increases in strength at 28 d in 20 and 5 ℃ environments, while alkaline accelerator shows strength collapse. Highly-concentration aluminum sulfate, conventional aluminum sulfate and hydrofluoric acid are hydrated to generate ettringite (AFt) and calcium silicate hydrate (C-S-H) gel to provide early strength and shorten the setting time, while sodium aluminate accelerator is through the consumption of gypsum and the generation of C-S-H and calcium hydroxide (CH) to provide early strength and shorten the setting time. The low-temperature environment will reduce hydration products content such as AFt and C-S-H in cement acted by high-concentration aluminum sulfate, conventional aluminum sulfate, and hydrofluoric acid-based accelerator, resulting in a decrease in strength. The hydration product of cement mixed with sodium meta-aluminate type accelerator is reduced by the generation of CH under the influence of low-temperature environment, which is able to attenuate the adverse effect of CH on the late strength.

Rheological Analysis of Workability for Tuff Manufactured Sand Concrete

WEN Hongping, SONG Pengfei, WANG Yuan, GAN Long, WANG Xuhao

2024, 43(1):  71-83. 

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The production and application of manufactured sand (MS) provide an excellent opportunity for China’s concrete industry to move towards low-carbon development. However, the complex characteristics of MS lead to poor workability and difficulty in prediction of concrete. In order to study the influencing factors and variation laws of workability for MS concrete based on rheological properties, this paper explored from two aspects: the characteristics of MS and concrete mix proportion parameters. Two-dimensional and three-dimensional relationship models between rheological properties and workability were established, and the significance of factors affecting the workability of tuff MS concrete based on rheological analysis was analyzed by grey relational analysis method. The experimental results show that the dynamic yield stress and plastic viscosity are closely related to the workability of concrete. With the increase of powder content, MS replacement rate, and sand ratio, the dynamic yield stress decreases first and then increases. The correlation between MS characteristics and various rheological properties of concrete is in a strongly correlated range. By properly adjusting the levels of these factors, the optimal workability required for actual engineering can be achieved.

Preparation and Shrinkage Performance of Porous Basalt Coarse Aggregate HPC

SUN Jing, HONG Junzhe, WANG Shen, CHANG Pu, JIA Xiaojing, LIU Hongbo

2024, 43(1):  84-91. 

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In order to solve the problems of high viscosity, difficult mixing and poor durability of high performance concrete (HPC) caused by large water absorption rate and fast early water absorption of porous basalt coarse aggregate, additional water consumption was introduced to prepare pre-wetted aggregate before preparation. The effects of different additional water consumption on workability, mechanical performance, shrinkage performance, pore structure and microstructure of porous basalt concrete were studied. And the performance of porous basalt concrete was compared with that of ordinary crushed stone concrete. The results show that when the additional water consumption is 4% or 6%(calculated by mass fraction of porous basalt coarse aggregate), the HPC with C60 compressive strength grade, excellent workability and low shrinkage can be obtained. Compared with ordinary gravel concrete, pre-absorbed porous basalt can significantly reduce the autogenous shrinkage of HPC, and has little effect on compressive strength. The self-shrinkage rate decreases with the increase of additional water consumption, and its development is divided into four stages of rapid growth, short-term expansion, slow growth and stabilization. The water-bearing basalt has internal curing effect, which can refine the pore structure in the later stage of hydration, improve the compactness of the interfacial transition zone and reduce the cracking risk of HPC.

Effect of Cooling Method after High Temperature on Mechanical Properties of Basalt Fiber Reinforced Concrete

PANG Jianyong, ZHENG Ruiqi, HU Xiuyue, SUN Jian, XU Guoping, SU Yongqiang

2024, 43(1):  92-101. 

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The mechanical property of concrete after high temperature treatment is one of the important indexes to evaluate the safety performance of concrete structure in engineering construction. The mechanical properties of concrete with different basalt fiber (BF) content were tested. The optimal basalt fiber reinforced concrete (BFRC) and ordinary concrete (OC) were subjected to high temperature treatment (200, 400, 600, 800 ℃). The effects of different cooling methods (natural cooling and spray cooling) on the performance degradation of BFRC after high temperature were studied, and the mechanical properties of BFRC under different temperatures and cooling methods were analyzed. The results show that when the content of BF is 0.05% (volume fraction), the compressive strength and splitting tensile strength of BFRC reach the maximum values of 50.2 and 3.5 MPa, which are 14.87% and 34.62% higher than those of OC, respectively. The incorporation of BF can effectively increase the toughness of concrete and the ability to resist cracking. With the increase of temperature, the elastic modulus of BFRC specimen decreases, but the elastic modulus of BFRC specimen is always greater than that of OC specimen. The peak strain of OC is greater than that of BFRC under the same cooling method, and the ductility index under different cooling methods is higher than that under normal temperature.

Mechanical Properties of SiO₂/KH560 Modified Basalt Fiber Reinforced Concrete

YANG Xin, YU Kui, JI Fengchun, NIE Tangzhe, LI Ke, BAI Tian

2024, 43(1):  102-112. 

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To study the effect of silane coupling agent (KH560) and nano-SiO₂ synergistically KH560 modified basalt fiber (BF) on the mechanical properties of concrete, KH560 was used to surface modify for BF to produce KH560-BF, and nano-SiO₂ and KH560 were used to modify BF to produce SiO₂-KH560-BF. Orthogonal tests were used to screene high-strength modified fibers, and the effects of mass fractions of nano-SiO₂ dispersion, lubricant and KH560 on the filament bundle strength of SiO₂-KH560-BF were investigated. The mechanical properties of modified concrete at 7 and 28 d were evaluated and the microstructure of the concrete was characterized by SEM and EDS. The results show that the optimal upper agent composition for SiO₂-KH560-BF is nano-SiO₂ dispersion 1.6%, lubricant 0.4%, and KH560 0.5%, and the degree of influence of the three factors is nano-SiO₂ dispersion>KH560>lubricant. Compared with KH560-BF, the fiber tow strength of SiO₂-KH560-BF increases by 8.62%, tensile strength increases by 4.41%, Si content increases by 24.9%, and there were fewer agglomerated buildups in the SEM images of SiO₂-KH560-BF than those of KH560-BF. The 7 and 28 d compressive, split tensile, and axial compressive strength enhancement effects of the concrete with a moderate amount of SiO₂-KH560-BF are higher than those of the concrete with KH560-BF.

Protective Behavior of Zinc Sacrificial Anode on Steel Bars under Carbonization and Chloride Salt Erosion

CHEN Libao, LIU Guangyan, JIN Linsen, MU Song, WANG Tao, TANG Jinhui

2024, 43(1):  113-120. 

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In this paper, with the metal zinc coated with cement-based materials as a sacrificial anode, the protective effect of sacrificial anode on steel bars was studied in concrete simulated pore solution to simulate carbonization and chloride ion erosion environments. The electrochemical test results show that when Q235 steel and pure zinc sheet form a galvanic pair, Q235 steel is prone to corrosion in a 1.5% (mass fraction) sodium chloride solution. However, adding an appropriate amount of alkali (LiOH) and halogen alkali metal compounds (LiBr) to simulated pore solution can stimulate the continuous dissolution of metallic zinc, continue to provide sacrificial anode protection and effectively inhibite the corrosion of steel sheets. Combined with XRD test results, it can be judged that LiOH can maintain zinc dissolution and generate zinc hydroxide, and the presence of halogen can induce corrosion of metallic zinc. Compared to halogen alkali metal compounds, adding high concentration of LiOH has a better rust resistance effect on steel bars. This study contributes to improve the excitation technology of sacrificial anode materials and enhance the protective effect of sacrificial anode technology on steel bars.

Effect of LDHs with Different Mg/Al Ratios on Corrosion Resistance of Steel Bar

YI Yuqi, LI Jing, WEI Liumei, TIAN Hao, ZHUANG Ende, LI Xuejie

2024, 43(1):  121-127. 

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In order to investigate the influences of Mg/Al ratios on crystal structure, anion controlled release ability and rust inhibition effect of MgAl-layered bimetallic hydroxides (MgAl-LDHs), MgAl-LDHs with Mg/Al molar ratios of 2∶1, 3∶1 and 4∶1 were synthesized by co-precipitation method. The phase composition of the synthesized samples was analyzed by XRD and FTIR. The chloride ion adsorption performance of the synthesized samples and their corrosion inhibition effect on steel bar in simulated concrete pore solution were studied by chloride ion adsorption and electrochemical experiments. The results show that with the increase of Mg/Al molar ratios from 2∶1 to 4∶1, the interlayer spacing of LDHs decreases from 0.888 nm to 0.796 nm, resulting in a decrease in the number of LDHs loaded anions and a decrease in chloride ion adsorption capacity. The critical chloride ion concentrations of Mg₂Al-NO^-₃, Mg₃Al-NO^-₃ and Mg₄Al-NO^-₃ doped groups are 0.16, 0.14 and 0.14 mol/L, respectively, which are 60%, 40% and 40% higher than that of the blank group (0.10 mol/L).

Effect of Composite Absorbing Material on Microwave Heating Property of Concrete

WU Gang, CHEN Wei

2024, 43(1):  128-137. 

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In view of the limitation of a single absorbing material to improve the microwave heating property of concrete, graphite powder and Fe₃O₄ were incorporated into concrete as composite absorbing material. The appropriate content of the composite absorbing material was determined by mechanical properties test. The effect of composite absorbing material on microwave heating property of concrete was studied by microwave heating test. The influence mechanism of the composite absorbing material was analyzed by electromagnetic parameter test. Meanwhile, the results were compared with those of the separate addition of graphite powder and Fe₃O₄. The results show that the addition of graphite powder and Fe₃O₄ can reduce the mechanical properties of concrete, and the content of absorbing material should not exceed 6% (mass fraction). The microwave heating property of concrete increases with the increase ofseparate addition of graphite powder and Fe₃O₄. When graphite powder and Fe₃O₄ are incorporated, the microwave heating property of concrete is better, and the best mix ratio is m(graphite powder)∶m(Fe₃O₄)=2∶1. When graphite powder and Fe₃O₄ are incorporated, the complex permittivity, dielectric loss angle tangent, complex permeability and magnetic loss angle tangent of concrete significantly increase, and the dielectric loss capacity and magnetic loss capacity significantly increase at the same time.

Prediction of Abrasion Resistance of Pervious Concrete Based on Machine Learning

BAI Tao, LUO Xiaobao, XING Guohua

2024, 43(1):  138-146. 

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The aim of this study is to utilize machine learning models for the prediction of the abrasion resistance of pervious concrete. 150 sets of pervious concrete abrasion resistance test data were collected and a database was constructed. 6 input parameters were identified using feature correlation analysis, namely maximum aggregate size, water/binder ratio, sand ratio, aggregate/binder ratio, fly ash ratio and rotation circle. A variety of machine learning algorithms (XGBoost, Gradient Boosting, AdaBoost, Decision Tree and Random Forest) were used to establish prediction models for the abrasion ratio of pervious concrete, and the model performance was characterized by coefficient of determination (R²), root mean squared error (RMSE) and mean absolute error (MAE). The results show that the Gradient Boosting model exhibits high accuracy and small prediction error on both the training and test sets, and the comparative analysis with the existing theoretical models confirms the advantages of the Gradient Boosting model in predicting the abrasion ratio of pervious concrete. The research results can provide a reference for the design and application of pervious concrete, and are expected to reduce the maintenance cost of related projects.

Solid Waste and Eco-Materials

Research Progress of Interfacial Bond Properties Between FRP Bars and Seawater Sea-Sand Concrete

KONG Lingyan, LIU Shuchang, BAO Jiuwen, YIN Xiangzhen, CAO Yinlong, CUI Yifei

2024, 43(1):  147-157. 

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The use of seawater and sea-sand for replacing river water and river sand in the production of seawater sea-sand concrete (SWSSC) can effectively solve the problems of high transportation costs of construction material and long delivery time for islands and reefs, marine and harbor engineering structure construction. However, corrosion of steel bars is exacerbated by the use of ordinary steel bars and seawater sand concrete in marine structures. In recent years, the application of fiber-reinforced polymer (FRP) reinforcement instead of ordinary steel bars in SWSSC can effectively solve the problem of chloride-induced steel corrosion in SWSSC. In this paper, the degradation law of the interfacial bond performance between FRP reinforcement and SWSSC was summarized. The failure mechanisms of bond strength of FRP reinforcement-concrete under different environments were analyzed. The effects of fiber type, embedding length, reinforcement diameter, surface type of FRP reinforcement and compressive strength of concrete on interfacial bond performance were discussed. Furthermore, the existing bond-slip constitutive models were further summarized. This review can provide a scientific basis for practical application of FRP reinforcement in SWSSC.

Advances in Acid Site Modulation Strategy after Zeolite Synthesis and Its Application in Catalytic Oxidation of VOCs

WANG Jianxiang, YUAN Jianhua, LIU Xiao, YANG Yun, YU Fei, MA Jie

2024, 43(1):  158-171. 

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Volatile organic compounds (VOCs) are a common source of pollution from industrial emissions, which are extremely toxic to human health and ecosystems. Catalytic oxidation is an energy-saving and efficient method for VOCs removal, and its key lies in catalyst design and development. The acid sites in zeolites can reduce the activation energy of VOCs oxidation reaction and effectively catalyze the oxidative degradation of VOCs, but the catalytic performance of pristine zeolites cannot meet the demand for VOCs catalysis. Through the post-synthesis modulation strategy, the density of acid sites in zeolites can be made higher, and their distribution is more favorable for the contact between VOC molecules and catalytic sites, so that the zeolite catalysts have more excellent catalytic performance. This review firstly introduces the formation of acid sites in zeolites and the techniques of characterizing the density and type of acid sites, and then focuses on the modulation strategies of acid sites after zeolite synthesis, including framework modification and internal/external surface modification, etc. Finally, this review lists the catalytic performances of zeolite catalysts obtained by the modulation strategies for VOCs. On the basis of the above, the future research direction of the acid site modulation strategies after zeolite synthesis is envisioned, which is of great significance to promote the application of zeolite catalysts in the efficient catalytic oxidation of industrial VOCs

Adsorption Properties and Mechanism of Ca-Montmorillonite with Different Layer Charge Numbers on AFB

XIAO Sha, PENG Tongjiang, SUN Hongjuan, ZHANG Wei

2024, 43(1):  172-182. 

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The adsorption properties and mechanism of AFB₁ on Ca-montmorillonite with different layer charge numbers were studied by using Ca-bentonite from Inner Mongolia, Xinjiang and Liaoning as the research object. The mineralogical properties, physical and chemical properties of bentonite from different producing areas and the adsorption kinetics and isothermal adsorption of AFB₁ by Ca-montmorillonite were studied by using X-ray diffractometer, infrared spectroscopy, high performance liquid chromatography and other testing methods. The results show that the bentonite from Inner Mongolia(N-Mt) with high Ca-montmorillonite content, large specific surface area and high layer charge numbers has better adsorption properties. When the initial concentration is 1.5 mg/L and the amount of adsorbent is 5 mg, the saturated adsorption capacity of AFB₁ is 1.153 mg/g, and the adsorption process is less affected by pH value. The adsorption behavior of AFB₁ on Ca-montmorillonite conforms to both the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, which indicates that the adsorption process may involve both physical adsorption and chemical adsorption, and the adsorption between Ca-montmorillonite and AFB₁ occurs at both interlayer and interlayer levels. The adsorption between Ca-montmorillonite and AFB₁ is mainly due to electron donor-acceptor binding and ion-dipole interaction between Ca-montmorillonite and AFB₁ molecules. The isothermal adsorption of AFB₁ by Ca-montmorillonite is more in line with the Langmuir model, which is a monolayer adsorption.

Adsorption of Polycarboxylate Superplasticizer by Silica Fume

ZHANG Jiangang, YANG Yong, MAO Yonglin, ZHOU Dongliang, LI Shenzhen, WANG Tao

2024, 43(1):  183-190. 

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Rapid and efficient dispersion of cementitious material containing large amounts of silica fume, microspheres, and other ultrafine powders is key technology for preparing ultra-high performance concrete. The interaction relation of polycarboxylate superplasticizer (PCE) and silica fume were studied by Zeta potential and total organic carbon method. The results show that surface charge of silica fume in water is negative, and has strong adsorption to PCE and its side chain monomermethacryloxypropyl polyethylene glycol ether (HPEG), while silica fume has weak adsorption to negatively charged main chain sodium polyacrylate (PAANa). In cement paste pore solution, the Zeta potential of silica fume is still negative, but the absolute value declines significantly, meanwhile the total adsorption amount of PCE and its side chain declines, while the adsorption amount of main chain increases. According to the fitting of Langmuir isotherm equation and theoretical calculation, it suggests that the adsorption of side chain structure of polycarboxylate by silica fume mainly comes from hydrogen bonding, which is weakened in cement paste pore solution.

Mechanical and NO_x Degradation Performance of TiO₂ Modified Steel Slag-Based Permeable Concrete

LIN Yuanming, LIN Jiafu, XIONG Xiaoli, YANG Zhengxian

2024, 43(1):  191-199. 

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TiO₂ modified steel slag-based permeable concrete (TSSPC) was prepared with nano-TiO₂ incorporated as photocatalyst, steel slag and slag powder as binder, and large steel slag particle as aggregate. The effects of TiO₂ content on the compressive strength, water permeability and NO_x degradation performance of TSSPC were studied. In addition, combined with microscopic test and analysis methods such as XRD and SEM-EDX, the effect mechanism of TiO₂ on the mechanical properties, water permeability and photocatalytic performance of TSSPC was investigated, laying the foundation for the application of TiO₂ in permeable concrete. The results show that when the TiO₂ content is low, the “nucleation effect” of TiO₂ particles promotes the early hydration of binder materials. However, when TiO₂ content is high, TiO₂ particles tend to agglomerate, which is harmful to the mechanical properties of TSSPC. In addition, as the TiO₂ content increases, the connected porosity and water permeability coefficient of permeable concrete increase. Compared with the blank control group, the connected porosity and water permeability coefficient of TSSPC with a TiO₂ content of 5% (mass fraction, the same below) increase by 4.5 percentage points and 1.34 mm·s^-1, respectively. The NO_x degradation efficiency of TSSPC increases as the TiO₂ content (0%～5%) increases. However, due to the agglomeration phenomenon, when the TiO₂ content exceeds 3%, the effect of increasing the TiO₂ content on NO_x degradation efficiency decreases significantly.

Soft Water Leaching Resistance Mechanism of Slag Cement Based Composites under Stray Current

HAN Yu, ZHAO Fangli, ZHAO Yitong, WANG Baomin

2024, 43(1):  200-208. 

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During the usage of railway transport, the complex environment leads to the decrease of durability of concrete structure. The effects of slag content, water-binder ratio and stray current voltage intensity on the microstructure of slag cement based composites under the coupling effect of stray current and soft water leaching were studied. The phase composition, Ca(OH)₂ content, microstructure and pore structure of slag cement based composites after 90 d calcium leaching were analyzed by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and mercury intrusion method. The results show that the larger the slag content, the less Ca(OH)₂ content in slag cement based composites, the lower the porosity, and the more uniform and dense the structure. With the increase of stray current voltage intensity, Ca(OH)₂ and AFt content in slag cement based composites decreases, and the phase boundaries of AFt and Ca(OH)₂ become blurred. C-(A)-S-H content in the material increases slightly, and the porosity decreases slightly. With the increase of water-binder ratio, Ca(OH)₂ content in the material decreases, the residual phase content decreases, the microstructure becomes loose and porous, the pore size structure coarsens as a whole, and the porosity increases.

Phase Transformation and Iron Separation Characteristics of High Iron and Low Silicon Red Mud Using Sodium Reduction

ZHENG Fuqiang, DAI Yanni, HU Bing, LIU Chen, OUYANG Siwen, HU Peiwei

2024, 43(1):  209-218. 

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The high-temperature roasting of red mud can realize the form transformation of iron, aluminum and silicon, making it easy to separate and recover. However, there are few reports about the difference and mechanism of sodium reduction roasting reaction of high iron and low silicon red mud. The effects of reduction temperature, Na₂CO₃ addition and reduction time on the phase transformation and microstructure of high iron and low silicon red mud were investigated by X-ray diffraction analysis, and the difference of iron magnetic separation after reduction reaction was also analyzed. The results show that sodium combines with aluminum and silicon elements to form sodium aluminosilicate during reduction roasting, which effectively destroys the compact structure of Fe and Al elements. Hematite and goethite are converted into magnetite and wustite mostly, which promotes the reduction of iron oxides. The low melting point sodium-containing solid solution reduces the migration resistance and accelerates the growth of metal iron grains. Based on the disintegration of the Fe-Al structure and the formation of coarse-grained metal iron, the roasted product is subjected to grinding-magnetic separation, and iron recovery indicator with the TFe content 90.41% and Fe recovery rate 93.08% is obtained.

Drying Shrinkage Performance of Geopolymer Concrete and Shrinkage Compensation of Active MgO

ZHANG Haixia, DONG Hao

2024, 43(1):  219-226. 

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A fly ash-slag-based geopolymer concrete was prepared, and the influence mechanism of active magnesia content, sodium silicate modulus, alkali equivalent and slag content on the compressive strength and drying shrinkage was explored and analyzed through 28 d compressive strength and drying shrinkage tests. The results show that with an increase of the active magnesia content, the 28 d compressive strength of the geopolymer concrete decreases, while the drying shrinkage deformation significantly diminishes. Compared with concrete specimen with 0% (mass fraction, the same bellow) active magnesium oxide content, concrete specimens with 3%, 6% and 9% magnesium oxide show a decrease of 8.0%, 8.2% and 18.2% in 28 d compressive strength, and a decrease of 21.5%, 26.4% and 38.2% in drying shrinkage, respectively. In addition, when the content of active magnesium oxide is 3% and 6%, it not only effectively compensates for drying shrinkage, but also reduces the loss of compressive strength. As the sodium silicate modulus increases, the 28 d compressive strength and drying shrinkage deformation of the geopolymer concrete increase. With higher alkali equivalent, the 28 d compressive strength of the geopolymer concrete decreases while the drying shrinkage deformation increases. With an increase in slag content, the 28 d compressive strength of the geopolymer concrete increases, and the drying shrinkage deformation decreases. Taking into consideration the requirements for both compressive strength and shrinkage, it is recommended that in practical applications, highly active magnesia be chosen with a content range of 3% to 6%.

Time-Varying Characteristics and Models of Mechanical Properties of High-Temperature Steam Curing Multi-Mixed Concrete

LIU Hao, HU Juan, JIN Qingping, LI Fan, ZHANG Xinsheng, YANG Zhao, LIAO Yishun

2024, 43(1):  227-235. 

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To study the time-varying characteristics and models of mechanical properties of mechanism sand concrete mixed with the fly ash and the slag (referred to as multi-mixed concrete) under high-temperature steam curing, combined with a high-temperature steam curing multi-mixed concrete precast beams of a highway project, steam curing-standard curing, steam curing-natural curing and standard curing modes were designed to test compressive strength, splitting tensile strength and elastic modulus of multi-mixed concrete at different periods. The relationship between compressive strength and splitting tensile strength, elastic modulus were explored. The results show that a suitable steam curing method can accelerate the growth of compressive strength, splitting tensile strength and elastic modulus of multi-mixed concrete, with the most significant effect on the development of compressive strength, and the mechanical properties don’t retract in the later stage. During the constant temperature stage of steam curing, the mechanical properties of concrete have the highest growth rate, followed by the heating stage, and the mechanical properties have the lowest growth rate during the cooling stage. Under steam-standard curing mode, time-varying model of compressive strength of multi-mixed concrete can take logarithm or logarithm and power function composite function, and the time-varying model of splitting tensile strength and elastic modulus can take power function.

Properties of Tailings Powder-Fly Ash-Cement Composite Cementitious System

LI Yongqing, NI Yongjun, LI Fangfang, GUO Weilong, CAO Xuanhao, GUAN Bowen

2024, 43(1):  236-245. 

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In order to explore the feasibility of the application of tailings powder in cement-based materials and improve the utilization rate of lithium tailings resources, the performance of tailings powder-fly ash-cement composite cementitious system was studied by using tailings powder produced in the process of lithium extraction and fly ash to partially replace cement. The results show that the flow performance of composite cementitious system can be improved by adding an appropriate amount of lithium tailings powder and fly ash. The early compressive strength of composite system is slightly reduced by adding lithium tailings powder and an appropriate amount of fly ash to partially replace cement, but it later strength is significantly increased. Compared with the control group, the 90 d compressive strength of experimental group with 5% (mass fraction) lithium tailings powder and 10% (mass fraction) fly ash increases by 9.75%, reaching 55.15 MPa. In the later stage of hydration, the composite activity effect and filling effect can be effectively exerted by mixing lithium tailings powder and fly ash, which can promote the formation of hydration products and fill them into macropores, increase the proportion of capillary micropores (< 10 nm) in cement paste, so as to refine the pore structure of cement paste and improve the density of system. Macroscopically, the compressive strength increases.

Influence Mechanism of Hornblende Ballast Machanical Sand and Stone Powder Content on Properties of Concrete

WANG Lichuan, LI Jing, YU Changbin, CAO Wenquan, LING Jianjun, WANG Qianqian

2024, 43(1):  246-256. 

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In order to clarify the influence of stone powder on the performance of concrete in the process of sand making by hornblenede ballast waste slag, the hornblende ballast waste slags from six areas in Hebei province surrounding Beijing and Tianjin Region were taken as experimental materials. The influence mechanism of hornblende ballast mechanical sand and stone powder content on the workability, mechanical properties and microstructure of concrete were investigated by mechanical tests, slump test, zata potential test, SEM and FTIR. The results indicate that except for Xinxin in the six regions, hornblende ballast mechanical sand can enhance compressive strength in all other regions. Wherein, Chengde and Xiaoshixia regions have the superior strengthening effect on concrete. Compared with concrete prepared by natural sand, after curing of 7 d, the compressive strength of C30 concrete prepared by Chengde and Xiaoshixia aggregate increases by 20.51% and 11.11%, and after curing of 28 d, the compressive strength increases by 10.79% and 6.58%, respectively. For C50 concrete, the compressive strength increases by 15.14% and 12.57% after curing 7 d, and increases by 14.55% and 16.55% after curing of 28 d, respectively. The optimal stone powder content of Chengde, Xinxin, Jiheng and Xiaoshixia is 8%～15% of cementitious material, but only about 5% for stone powder of Pingshan. Among, the stone powder content replacing cementitious materials in Chengde and Xiaoshixia regions is the highest. The reason is that the particle size of stone powder in these two areas is small. SEM shows that the stone powder shows obvious erosion and damage morphology under alkaline conditions, and more cementitious products are formed at the aggregate interface, which improves the degree of cementation between aggregate particles. In addition, the appropriate of stone powder content has a certain filling effect on the coarser manufactured sand concrete in Fengning area, which can improve the mechanical properties of concrete. The results of FTIR and Zeta potential tests show that the hornblende ballast waste slag rock powder can adsorb the polycarboxylate superplasticizer and react to form ionic compounds. The polycarboxylate superplasticizer improves the stability of the stone powder, cement and polycarboxylate solution system. This study can provide a reference for the application of hornblende ballast mechanical sand in ordinary concrete and the proportion design of stone powder replacing different cementitious materials in concrete.

Preparation and Performance of All-Solid Waste Recycled Fluid Mixture

ZHOU Wenjuan, HU Niutao, NIU Haoxiang, XIE Qian

2024, 43(1):  257-267. 

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Alkali slag, slag, redundancy soil and brick concrete fine aggregate were used as raw materials to prepare all-solid waste recycled fluid mixture. Through the tests of fluidity, setting time and compressive strength, the influence of composition and total amount of the cementitious material on the working performance and mechanical properties of fluid mixture were discussed, and the reasons for its performance changes were analyzed by XRD and SEM. The test results show that: in the range of 15%~50% of alkali slag, 20%~85% of slag, and 0%~40% of fly ash, the strength of fluid mixture is up to 1 MPa. The slag content has the most significant impact on the early and later compressive strength growth of fluid mixture. The effect of alkaline waste slag and fly ash content on the later compressive strength growth of fluid mixture is significant. Through microscopic analysis, the strength of fluid mixture is mainly attributed to the depolymerization of slag in an alkaline environment, and the interweaving of C-S-H, C-A-S-H and AFT to form a skeleton.

Performance of Desulfurization Building Gypsum Modified by Inorganic Cementitious Materials

SHAN Junhong, ZHANG Ze, GAO Peng, WANG Kui

2024, 43(1):  268-275. 

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Circulating fluidized bed (CFB) ash has good volcanic ash properties, desulfurization building gypsum was used as the main cementitious material, carbide slag was used as an alkali activator, CFB ash and fly ash were used as mineral additives to study the effect of CFB ash on the fluidity, setting time, compressive strength and expansion rate of desulfurization building gypsum. The hydration products and microstructure were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and other methods. The results show that adding CFB ash can effectively improve the mechanical property and water resistance of desulfurization building gypsum, but it has a negative impact on its workability and expansiveness. After composite modification with 20% (mass fraction) CFB fly ash and 5% (mass fraction) carbide slag, the absolute dry compressive strength of desulfurization building gypsum at 1 and 28 d is 20.53 and 22.37 MPa, which increases by 28.6% and 35.9% compared to desulfurization building gypsum based samples, respectively. The calcium silicate hydrate (C-S-H) gel and ettringite (AFt) generated from the hydration of CFB ash are wrapped and filled in the crystal surface and voids of dihydrate gypsum, making the internal structure of the hardened body more compact, thus improving the mechanical property and water resistance of desulfurization building gypsum.

Modeling of Irregular Recycled Aggregates and Numerical Simulation of Recycled Aggregate Concrete

HU Yanbo, GAO Peng, LI Jingzhe, ZHANG Guohui, WANG Guotao, DONG Shuaizhi, CHU Yuting, ZHAN Binggen, YU Qijun

2024, 43(1):  276-286. 

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Traditional recycled aggregate concrete (RAC) models mostly use basic geometries to represent recycled aggregate (RA) structures, which is quite different from the actual situation. In this paper, a real two-dimensional aggregate database was constructed by combining digital image technology and Fourier descriptor method, and a new method for random generation of RA based on aggregate overlap method was proposed. A new rapid placement algorithm suitable for Fourier reconstituted aggregate was proposed based on the coarse determination of the outer rectangular box/inscribed circle and the fine determination based on the overlap box. And the construction of RAC meso-structure with different RA substitution rates and RA residual mortar content was realized. Based on the cohesive zone model, a numerical model was established based on the meso-structure of randomly generated RAC, and the effects of RA substitution rate and RA residual mortar content on the uniaxial tensile performance of RAC were studied. The results show that the tensile strength and elastic modulus of RAC decrease with the increase of RA substitution rate and RA residual mortar content, but the peak strain does not change much. The RA model is more realistic, and the content and distribution of adhesion mortar can be adjusted independently.

Preparation and Hydration Characteristics of Alkali Excited Municipal Solid Waste Incineration Bottom Ash Geopolymer

LIU Gang, LI Xincheng, LIU Jinjun, JIAN Shouwei, FAN Lulu, TU Liangliang

2024, 43(1):  287-294. 

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To prepare the bottom ash geopolymer, municipal solid waste incineration bottom ash (BA), metakaolin and granulated blast furnace slag were selected as raw materials, and NaOH and water glass were adopted as alkali activators. The effects of different alkali content and BA content on compressive strength of geopolymer and hydration characteristics were mainly investigated. The results show that, when the alkali content reaches 7% (mass fraction, the same below), the reaction between excess sodium and active silicon, calcium and aluminum causes a large amount of low-strength N-A-S-H, which decreases the strength of bottom ash geopolymer. When the alkali content remains constant and the BA content reaches 80%, the strength of bottom ash geopolymer decreases substantially. Regarding bottom ash, its geopolymer system has a significant curing effect on heavy metal ions. Therefore, bottom ash geopolymer preparing by BA is of great significance for green recycling of municipal solid waste and environmental protection.

Pozzolanic Activity Test and Evaluation Method of MSWIFA

CHEN Jiaqing, CHEN Ping, XIE Yumeng, WANG Yin, WANG Ziang, ZHAN Liangtong

2024, 43(1):  295-301. 

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Resource utilization of municipal solid waste incineration fly ash (MSWIFA) is attracting attention, and the pozzolanic activity of MSWIFA is an important property for its utilization. However, there has yet no reliable evaluating methods. Given that fly ash and MSWIFA are both incineration products, borrowing the existing pozzolanic activity methods of fly ash, two types of MSWIFA (from grate furnace and fluidized bed) were tested and analysized by pozzolanic activity test from three perspectives, such as material composition (composition structure analysis method), cementation properties (strength activity index method) and chemical reaction (combined water content method), and compared with the test results of three grades of fly ash. The results show that the composition structure analysis method and strength activity index method are suitable for evaluating pozzolanic activity of MSWIFA, and the combined water content method is not suitable. The amorphous phase silica-alumina content can characterize pozzolanic activity of MSWIFA and correlated with strength activity index. The results of strength activity index method are affected by relation content of amorphous phase silica-alumina content and calcium. The strength activity index of 14 d can characterize pozzolanic activity of MSWIFA, the strength activity index of 90 d or even more curing ages can better characterize pozzolanic activity of fly ash.

Ceramics

Evolution and Mechanism of Friction and Wear Properties of Silicon Nitride Ceramics at High Temperature

LIU Wenjin, ZHOU Guoxiang, YANG Zhihua, JIA Dechang

2024, 43(1):  302-311. 

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Si₃N₄ ceramics have attracted much attention in the field of high temperature wear resistance because of high temperature resistance, corrosion resistance, wear resistance and hardness. In this paper, the plane friction and wear properties and mechanism of Si₃N₄ ceramics when wearing with C/SiC ceramics or GH214 superalloy at high temperature were investigated. The results show that the friction coefficient of Si₃N₄ ceramics against C/SiC ceramics increases first and then decreases with the increase of temperature. The average friction coefficient of Si₃N₄ ceramics at 1 200 ℃ is lower than 0.4, and wear marks, wear particles and SiO₂ oxide film appear on wear surface. The wear forms are mainly abrasive grain wear and oxidation wear. When Si₃N₄ ceramics and GH214 superalloy are worn against each other, the friction coefficient increases with the increase of temperature. Meanwhile, obvious metal oxide layer is formed on the surface of ceramic samples, so the wear forms are mainly adhesive wear and oxidation wear. During the friction process of Si₃N₄ ceramics and two kinds of friction materials, the oxide film produced by oxidation wear has protective and lubricating effects on Si₃N₄ ceramics, which can effectively reduce the wear of Si₃N₄ ceramics matrix and improve the wear life of Si₃N₄ ceramics.

Effects of Carbon Sources on Properties of Reaction-Bonded Silicon Carbide

ZHANG Xifei, CHEN Ding, GU Huazhi, HUANG Ao, FU Lvping

2024, 43(1):  312-316. 

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The carbon black and graphite were used as carbon sources to fabricate reaction-bonded SiC, and the total content of carbon sources was 10% (mass fraction, the same below). The effects of different ratios of carbon black and graphite on properties of reaction-bonded SiC were investigated. The results show that the reaction-bonded SiC with 4% carbon black and 6% graphite has good mechanical properties, the flexural strength and fracture toughness reach to 251.7 MPa and 4.29 MPa·m^1/2. The mineral composition of reaction-bonded SiC was measured by XRD, the Rietveld simulation results of XRD patterns were adopted to measure phase content. The free Si content in reaction-bonded SiC with 4% carbon black and 6% graphite is 24.44% (mass fraction). The free Si content in reaction-bonded SiC with 10% graphite reaches to 28.57% (mass fraction), which is higher than that of the former. The decrease of free Si contributes to the improvement of mechanical properties of reaction-bonded SiC.

Effect of Polyethylene Glycol on Pot Life and Performances of Silicate Adhesives

SHEN Zhenqiang, WANG Yudan, CAO Xianqi, SONG Laiming, XUE Jinlong, WANG Chao

2024, 43(1):  317-328. 

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In order to solve the problem of short pot life to surface curing of silicate adhesives into film when exposed in air, the adhesives were modified by adding polyethylene glycol (PEG) to silicate adhesives, and the pot life, rheological performance, microscopic morphology, molecular structure, thermal stability and adhesive performance were systematically studied by using rheometer, scanning electron microscope, infrared spectrometer, thermogravimetric infrared mass spectrometer and universal tensile machine. The results show that when the PEG dosage in silicate adhesives is 6% (mass fraction), the pot life is extended to 50 min. The PEG is uniformly distributed inside adhesive, which significantly enhances the densification and thixotropy. The pre-curing activation energy calculated by Arrhenius equation increases from 8.47 kJ/mol to 12.61 kJ/mol. PEG does not affect the bonding performance of system and has a good extension effect on the pot life of same types of silicate adhesives.

Preparation of Foamed Ceramics from Granite Waste and Glass Waste Residue

ZHAO Chenglin, YUAN Wenhai, DONG Yiran, JIANG Congcong, HE Biao, HUANG Shifeng, CHENG Xin

2024, 43(1):  329-338. 

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In this paper, all-solid waste foamed ceramics with high porosity and low water absorption were prepared by powder sintering method, using granite waste and glass waste residue as raw materials and SiC as foaming agent. The effects of mix ratio of granite waste and glass waste residue, sintering temperature, and foaming agent content on pore structure and properties of foamed ceramics were explored. The results show that granite waste forms a framework structure of foamed ceramics, while glass waste residue has a melting aid effect. When glass waste residue content is 20% (mass fraction), the sintering temperature decreases by 40 ℃. The compressive strength of foamed ceramics prepared at 1 110~1 150 ℃ is 2.23~0.41 MPa, the bulk density is 468.41~326.31 kg/m³, the porosity is 79.15%~86.81%, the water absorption rate is 0.96%~1.00% and the average pore size is 0.49~1.43 mm, which effectively regulates the pore size of foamed ceramics and meets the needs of different application scenarios for different pore sizes of foamed ceramics. This study provides technical support for the large-scale utilization of granite waste and glass waste residue, as well as the preparation of foamed ceramics with different pore sizes.

Effects of MgO and La₂O₃ Composite Additives on Microstructure of Nano-Microcrystalline Alumina Ceramics

LI Hui, ZHANG Jinping, GAO Jingxia, WANG Erping, ZHANG Yangyang

2024, 43(1):  339-346. 

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The nanocrystalline alumina abrasive, with its excellent versatility and high-precision grinding capability, has become a cost-effective choice for various applications in fields such as mechanical manufacturing, bearings, molds and automobiles. In this study, nano microcrystalline alumina was synthesized by sol-gel process, with boehmite (γ-AlOOH) as raw material, MgO and La₂O₃ as additives. The effects of MgO and La₂O₃ additives on the phase transformation, phase composition, microstructure and mechanical properties of nanocrystalline alumina were investigated by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and ab initio molecular dynamics simulation. The results show that MgO and La₂O₃ composite additives can reduce the transformation temperature of alumina from the intermediate phase θ-Al₂O₃ to α-Al₂O₃ from 1 257 ℃ to 1 105 ℃, lower the densification temperature of the material from 1 600 ℃ to1 350 ℃, and reduce the grain size of nanocrystalline alumina from 1.04 mm to 120 nm, thus realizing the low-temperature dense sintering.

Glass

Research Progress on Preparation of Glass-Ceramics from Stainless Steel Slag

SHEN Yue, ZHOU Yahui, JIA Lu, JIA Luyao, LI Hao, YAO Bin, DENG Leibo

2024, 43(1):  347-353. 

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The rapid development of industry leads an increase in solid waste production year by year, and the environmental and resource issues it brings cannot be ignored. Using industrial solid waste in the form of glass-ceramics is one of the important ways of solid waste resource utilization. At the same time, this method can also reduce environmental damage by solidifying heavy metals. Based on the sources and characteristics of stainless steel slag, the common methods of harmless treatment of stainless steel slag are compared and analyzed. In view of the harmless treatment and resource utilization of stainless steel slag, this paper focuses on the influences of main components on the structure and properties of glass-ceramics in the process of preparing glass-ceramics materials from stainless steel slag. In addition, based on the research status of solidification of heavy metals by glass-ceramics, the harmless treatment of Cr, Ni and Mn in stainless steel slag cured by glass-ceramics is analyzed and discussed. Finally, the future research directions of harmless treatment and resource utilization of stainless steel slag are prospected.

Preparation of Low Expansion Borosilicate Glass Based on Regeneration of Waste Liquid Crystal Glass and Its Physicochemical Properties

TIAN Yingliang, YUAN Zhichun, ZHAO Zhiyong, MU Guanghan, HE Feng

2024, 43(1):  354-362. 

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Based on the high-value recycling of waste liquid crystal glass, low expansion borosilicate glass was prepared with waste liquid crystal glass as main raw material, and quartz sand, boric acid and soda ash as the auxiliary materials. By buoyancy method, indentation method, quartz expansion method and weight test method, the influences of waste liquid crystal glass content and auxiliary raw materials (Na₂O and B₂O₃) on the physicochemical properties of glass were explored. The results show that with the increase of waste liquid crystal glass content, glass density, linear thermal expansion coefficient and acid-resistant mass loss increase, while Vickers hardness and alkali-resistant mass loss decrease. With the increase of Na₂O content in auxiliary raw materials, the glass density, linear thermal expansion coefficient, acid-resistant mass loss and alkali-resistant mass loss increase, while Vickers hardness decreases. With the increase of B₂O₃ content in auxiliary raw materials, the glass density and Vickers hardness decrease, and linear thermal expansion coefficient and acid- and alkali-resistance mass loss increase. When the mass fraction of Na₂O and B₂O₃ in waste liquid crystal glass and auxiliary raw materials are 60.00%, 1.00% and 14.72%, respectively, the Vickers hardness of glass is the highest, and density and linear thermal expansion coefficient of glass are the lowest, which are 7.143 0 GPa, 2.309 7 g·cm^-3 and 3.531 7×10^-6℃^-1, respectively. When the mass fraction of waste liquid crystal glass and Na₂O and B₂O₃ in auxiliary raw materials are 60.00%, 3.00%, 9.72%, the mass loss of acid resistance is the smallest, which is 0.614 0 mg·cm^-2. When the mass fraction of waste liquid crystal glass and Na₂O and B₂O₃ in auxiliary rawmaterials are and 70.00%, 2.00%, 11.67%, the mass loss of alkali resistance is the smallest, which is 1.214 0 mg·cm^-2。

New Functional Materials

In-Situ Synthesis of Hydroxyapatite by Biomimetic Mineralization Assisted by Graphene Oxide

ZHANG Biao, SHI Qiming, BAI Ziheng, LIU Hongyu, MA Tao, WANG Fen, ZHU Jianfeng, SHI Pei

2024, 43(1):  363-369. 

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Hydroxyapatite (HAp) is an inorganic material similar to human bone, with good biocompatibility. In this paper, HAp nanoparticles were in-situ synthesized using simulated body fluid (SBF) biomimetic mineralization method with graphene oxide (GO) as a template. The effects of mineralization time and volume ratio of SBF to GO on the phase composition, morphology, and structure of mineralization products were studied through testing and analysis of SEM, XRD, EDS and Raman spectroscopy. The results show that a large amount of uniformly distributed bone-like HAp is formed on the surface of GO after mineralization treatment. With the extension of mineralization time and the increase of volume proportion of SBF, the size and quantity of mineralization products increase, and the interlayer spacing of GO gradually expands. This study verifies the feasibility of synthesis of HAp nanoparticles assisted by graphene oxide, and expands the application field of biomimetic mineralization method.

Preparation of EDTA-LDH/Zeolite and Its Adsorption of Heavy Metal Ions

XIE Xiuxin, LIAO Libing, LEI Xinyu, WANG Lijuan, TANG Xiaowei

2024, 43(1):  370-382. 

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EDTA-LDH/zeolite composite material was synthesized in two steps by hydrothermal and reconstruction method and used for the removal of Cd²⁺, Pb²⁺, and Cu²⁺ from aqueous solution. The adsorption effect and mechanism of EDTA-LDH/zeolite on Cd²⁺, Pb²⁺ and Cu²⁺ in single and mixed heavy metal ion solutions under different conditions were systematically investigated. The results show that the best adsorption performance of EDTA-LDH/zeolite is achieved when the dosage of EDTA-LDH/zeolite is 0.05 g, the concentration of heavy metal ions is 1 500 mg/L, the pH value is 6.5, and the adsorption time is 24 h. Competing adsorption between heavy metal ions, the maximum adsorption capacities of EDTA-LDH/zeolite for Cd²⁺, Pb²⁺, and Cu²⁺ are 65.33, 98.35, and 108.51 mg/g, respectively. During the removal process, various mechanisms such as precipitation, surface complexation, and chelation work synergistically. The removal behavior of EDTA-LDH/zeolite are all consistent with Langmuir isotherm model and pseudo second-order kinetic model.