Table of Content

Volume 44 Issue 7
15 July 2025

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Cement and Concrete

Research Progress on Corrosion Behavior of Hydraulic Lime

CAO Ruidong, WANG Yibo, ZHAO Jie, CHEN Haojie, DUAN Rui, REN Linjie

2025, 44(7):  2355-2367.  doi:10.16552/j.cnki.issn1001-1625.2024.1380

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Hydraulic lime is widely used in the restoration of historical buildings and geotechnical heritages due to its excellent performance and strong affinity with cultural relics. This paper introduces the preparation and properties of hydraulic lime, and summarizes the macroscopic performance changes of hydraulic lime in three types of corrosive environments: acid, alkali and salt, the performance improvement after modification and the microscopic deterioration mechanism, aiming to reveal the mechanism of the corrosion behavior of hydraulic lime. The research shows that salt environments cause the most damage to hydraulic lime; acid environments are second; and alkaline environments are the least. The durability of hydraulic lime can be improved by lowering the water cement ratio, adding volcanic ash materials and incorporating modifiers to improve the hydraulic lime generators, porosity and micro-morphology. Finally, the deficiencies of the research on hydraulic lime at this stage are pointed out, which provides reference and enlightenment for the research and development of hydraulic lime to deal with the actual environmental problems and new building repair materials.

Effects of Curing Methods on Hydration and Mechanical Properties of Magnesium Silicate Cement

LI Xiangguo, BAO Luchao, HE Chenhao, ZHANG Chengshan, LYU Yang

2025, 44(7):  2368-2377.  doi:10.16552/j.cnki.issn1001-1625.2024.1633

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As a new type of green and low-carbon building material, magnesium silicate cement (MSHC) has the advantages of light, porosity, low alkalinity and low hydration heat, but it also has some problems such as slow development of mechanical properties in the early stage and easy cracking in the later stage. In this paper, the effects of curing methods such as high temperature (50 ℃) curing, high water absorbent resin (SAP) curing, SAP+high temperature (50 ℃) curing on the mechanical properties of MSHC were discussed, and the mechanism was analyzed by XRD, SEM, comprehensive thermal analysis and solid state nuclear magnetic resonance silicon spectroscopy. The results show that compared with high temperature (50 ℃) curing or SAP curing alone, SAP+ high temperature (50 ℃) curing can significantly improve the early compressive strength of MSHC, promote hydration reaction, and its 3 and 28 d compressive strength can reach 34.8 and 61.0 MPa, respectively. High temperature curing accelerates the formation of MgO-SiO₂-H₂O (M-S-H) gel. SAP+high temperature (50 ℃) curing method can more effectively promote the hydration of MgO and generate more M-S-H gel.

Flexural Properties and Cyclic LoadingPerformance of SMAF-FRCC

XU Longfei, LIU Shixi, LI Yanjie, YANG Lingqiang

2025, 44(7):  2378-2387.  doi:10.16552/j.cnki.issn1001-1625.2024.1296

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Superelastic shape memory alloy fibers (SMAF) were randomly interspersed within a modified polypropylene (PP) fiber-reinforced cementitious composite (FRCC) mixture to fabricate self-centering shape memory alloy fiber reinforced cementitious composite (SMAF-FRCC) composite beam specimens. This study investigated the effects of the diameter, content, and length of SMAF on the flexural strength, self-centering performance, and energy dissipation capacity of SMAF-FRCC composite beam specimens. The results demonstrate that the addition of SMAF significantly improves the flexural strength, self-centering performance, and energy dissipation capacity of the composite beam specimens, enhancing the material's ductility and toughness. Among them, When the length of SMAF is 25 mm and the content is 0.50% (volume fraction), flexural strength of the specimens is the highest, which is increased by 21.84% compared with the control group. When the length of SMAF is 20 mm and the content is 0.75% (volume fraction), the self-centering performance of the specimen is the best as a whole. In the last cycle of the cyclic loading flexural test, the self-centering ratio is increased by 19.57% compared with the control group. The study provides experimental evidence for the future development of SMAF-FRCC smart material systems with crack self-healing and deflection self-centering capabilities.

Preparation of Aluminum Silicon Composite Microcapsules and Application in Cement-Based Materials

WU Qingyong, ZHAO Shuang, HAN Bin, WANG Wei, QIAO Min, DU Shuang, CHEN Junsong

2025, 44(7):  2388-2395.  doi:10.16552/j.cnki.issn1001-1625.2024.1561

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In order to realize the slow-controlled release of inorganic salt-accelerating materials in cement-based materials and achieve the effect of time-varying regulation of cement setting and hardening, in this paper, aluminum sulfate (AlS) was used as the core material and tetraethyl orthosilicate (TEOS) was used as the precursor to prepare aluminum silicon composite microcapsules (SiO₂-AlS) with nano-SiO₂ as the shell and AlS as the core. The structure of SiO₂-AlS was characterized by nitrogen adsorption specific surface area method, laser particle size analysis, X-ray diffraction and scanning electron microscopy. The feasibility of the preparation method was verified, and the slow-release effect and application performance of SiO₂-AlS were investigated. The results show that the prepared SiO₂-AlS shows slow-release effect in solution, which can promote the hydration process of cement, shorten the setting time, and improve the early compressive strength of cement-based materials. However, SiO₂-AlS has little effect on the initial fluidity of cement-based materials, which can meet the construction requirements.

Effects of Fiber Types on Mechanical Properties and Microstructure of Engineered Cementitious Composites

HAO Rusheng, HU Wei, HE Jingjing, WU Wenbo, LU Haodan, ZHANG Wei

2025, 44(7):  2396-2405.  doi:10.16552/j.cnki.issn1001-1625.2024.1388

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To investigate the reinforcement mechanism of different fibers on engineered cementitious composites (ECC), the in-situ manufactured sand from a certain project site and three types of fibers (polyvinyl alcohol (PVA), polypropylene (PP) and polyethylene (PE)) were used to prepare ECC. The mechanical properties and microstructure of ECC prepared by PVA fibers, PP fibers and PE fibers were compared with the matrix. The distribution pattern of ECC bending cracks was characterized by digital image processing technology. The results show that the incorporation of fibers results in a reduction in the compressive strength of the matrix. Among them, the reduction in compressive strength is smallest for polyethylene PE fibers. The 28 d compressive strength of ECC prepared by PE fibers (E-PE) is 52.5 MPa. In terms of flexural performance, the flexural toughness and ultimate deflection of ECC are enhanced compared to the matrix. E-PE exhibits the best flexural performance, its peak load and ultimate deflection are 5.51 kN and 3.40 mm. With the increase of flexural deflection, the bending crack length and crack area of ECC increase. The crack area of E-PE is only 40.455 9 mm² when the deflection is 3.0 mm. Distinct failure mechanisms are observed for different fibers. PVA and PP fibers exhibit pullout failure, while the specimens exhibit single crack toughness failure. PE fibers show a combination of pullout and breakage, its specimen shows multi point cracking failure mode.

Grouting Reinforcement of Water-Rich Sand Layers Based on Paste Rheological Theory

WANG Zhe, YOU Wei, LI Pengfei, LIANG Qimin

2025, 44(7):  2406-2418.  doi:10.16552/j.cnki.issn1001-1625.2024.1550

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Grouting reinforcement is a common method to solve the liquefaction problem of water-rich sand soil in tunnels. Currently, traditional grouting materials have poor mechanical properties, low compressive strength, and high brittleness. There is relatively little research on the impact of the flow performance of grouting materials on the grouting reinforcement effect. This study designed a grouting reinforcement test for sand soil based on the rheological properties of grouting materials. Portland cement, fly ash, and polycarboxylate superplasticizer were used as raw materials, and high mechanical properties self-compacting paste was used as the grouting material for grouting simulation and on-site engineering tests. The study revealed the impact of the flow performance of grouting materials on grouting pressure, grouting diffusion range, and the mechanical properties of sand soil. The results show that self-compacting paste is an excellent grouting material with high compressive strength and high dynamic elastic modulus, and it has the characteristic of controllable flow performance. The slump flow of the paste is directly proportional to grouting pressure, grouting volume, and the lateral diffusion range of grouting. The viscosity of the slurry is inversely proportional to grouting pressure and vertical diffusion depth. Finally, improvement suggestions are proposed for the grouting method of water-rich sand layers from the aspects of single-hole grouting volume and grouting process. Self-compacting paste shows significant reinforcement effects in on-site grouting tests and is conducive to its wide application in the field of foundation reinforcement.

Mechanical Properties and Permeability Resistance of Silane-Modified Graphene Oxide Enhanced Cement Mortar

HUANG Weilin, YU Jinru, SHANG Jun, WANG Zhongtang

2025, 44(7):  2419-2428.  doi:10.16552/j.cnki.issn1001-1625.2024.1617

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In order to improve the performance of concrete in harsh environments, γ-(2,3-epoxypropoxy) propyltrimethoxysilane (GOPS) modified graphene oxide (GO) was prepared by sol-gel method to obtain silylated graphene oxide (fGO). Then the cement mortar was filled with fGO and its mechanical properties were measured. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that compared with GO, the fGO structure is loosely layered, and the siloxane molecules are grafted with GO through the Si—O—C bond. Compared with the control group, fGO has little effect on the slump and slump flow of cement. When the content of fGO is 0.06% (mass fraction), the 28 d flexural strength and compressive strength of cement mortar increase by 26.36% and 36.29%, respectively, and the capillary water absorption and chloride ion diffusion coefficient decrease by 56.64% and 33.16%, respectively. Thermogravimetric and microscopic analysis show that fGO improved the morphology of hydration products, enhance the adhesion between hydration products and sand particles, and improve the integrity and stability of silicate network as a whole.

Mechanical and Microscopic Properties of Ferroaluminate Cement Concrete under Action of Seawater Dry-Wet Cycle

ZHANG Pu, QI Dongyou, WANG Xiaoke, CHEN Heyuan, HE Changyu, ZHANG Wei, XIE Yabin, ZHANG Dong

2025, 44(7):  2429-2436.  doi:10.16552/j.cnki.issn1001-1625.2024.1414

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With the development of marine infrastructure construction in recent years, the durability requirements of cement-based materials in marine environments have been increasingly raised. Ferroaluminate cement is the "third-generation cement" in China, which has excellent performance of resistance to seawater erosion. The purpose of this study was to explore the mechanical properties and microstructural changes of ferroaluminate cement concrete (FACC) and ordinary Portland cement concrete (OPCC) under the seawater dry-wet cycle, with particular attention to the influence of water-to-cement ratio on the properties. The physical and mechanical properties such as mass loss rate, relative dynamic elastic modulus and cube compressive strength of FACC and OPCC were compared and analyzed by experiments, and the microstructure was analyzed by scanning electron microscope and mercury intrusion method. The results show that during the seawater dry-wet cycle, FACC has a lower mass loss rate, and the relative dynamic elastic modulus of FACC increases at the beginning of the seawater dry-wet cycle and then tends to be stable, while relative dynamic elastic modulus of OPCC shows a significant decrease in the later stage of the seawater dry-wet cycle. In terms of compressive strength, FACC increases after seawater dry-wet cycle, while OPCC decreases. Overall, FACC demonstrates superior durability and stronger resistance to seawater erosion compared to OPCC. Microscopic analysis reveals that FACC has lower porosity and finer pore structure, which contributes to improve its durability.

Mesoscopic Simulation Study on Uniaxial Compression of Distributing-Filling Coarse Aggregate Concrete

HUANG Sheng, SUN Jiangtao, LI Zhitang, ZHU Zilong, SHEN Weiguo, SUN Zhijun, TAN Zonglin, WANG Guiming

2025, 44(7):  2437-2446.  doi:10.16552/j.cnki.issn1001-1625.2024.1591

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In this paper, a two-dimensional concrete mesoscopic model containing macropores was established based on the random aggregate model. Based on verifying the reliability of the model, the damage and failure process of distributing-filling coarse aggregate (DFCA) concrete was studied, and the influences of different macro-porosities and DFCA ratios on the mechanical behavior of concrete were analyzed. The results indicate that, the damage in DFCA concrete first occurs near macropores and the interfacial transition zone of the reference aggregate, then develops in the interfacial transition zone of the DFCA, and finally develops to the mortar matrix. With the increase of macro-porosity, the compressive strength and elastic modulus of concrete decrease, and the increase of DFCA ratio weakens the influence of macropores on the properties of concrete. Under different DFCA ratios, the compressive strength and elastic modulus of concrete show a trend of first increase and then decrease. When the DFCA ratio is 20%, the compressive strength and elastic modulus of concrete reach their maximum values.

Improving Shrinkage and Cracking Resistance of Manufactured Sand Concrete Through Internal Curing with Super-Absorbent Polymer

ZHANG Wenlong, FENG Taotao, WANG Fengjuan, ZHANG Yu, WANG Xi, JIANG Jinyang

2025, 44(7):  2447-2457.  doi:10.16552/j.cnki.issn1001-1625.2024.1471

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To enhance the crack resistance of manufactured sand concrete in the arid and cold northwest environment(temperature 5 ℃,humidity 30%), super-absorbent polymer (SAP) was used as an internal curing material. Drying shrinkage, autogenous shrinkage, flat crackingand and compressive strength tests were conducted to analyze the effect of SAP on the early-age shrinkage cracking and mechanical properties of manufactured sand concrete. Isothermal calorimetry and thermogravimetric analysis were utilized to study the impact of SAP internal curing on cement hydration. The results indicate that SAP can effectively increase the early hydration degree of cementitious materials, reduce the risk of shrinkage and cracking of manufactured sand concrete in the arid and cold northwest environment, extend the cracking time of manufactured sand concrete, and reduce the cracking area. The effect of SAP after water absorption treatment is more significant, and the optimal SAP pre-absorption capacity is 6%. Further analysis through thermogravimetric and hydration heat tests reveal that SAP improves internal humidity through a water absorption and slow-release mechanism, prolonging the hydration reaction time and thereby enhancing crack resistance. However, the introduction of SAP increases porosity, leading to decrease concrete strength.

Effect of Pre-Wetted Biochar on Autogenous Shrinkage and Compressive Strength of Ultra-High Performance Concrete

HUANG Congbin, TAI Hongsheng, LUO Jugang

2025, 44(7):  2458-2464.  doi:10.16552/j.cnki.issn1001-1625.2025.0201

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To address the issue of compressive strength reduction in internally cured ultra-high performance concrete (UHPC), this study investigates the effects of pre-wetted biochar with different particle sizes, as a replacement for fly ash, on the fresh properties, autogenous shrinkage, compressive strength, pore structure, and microstructure of UHPC. The results demonstrate that the incorporation of pre-wetted biochar significantly enhances the internal humidity of UHPC and effectively reduces its autogenous shrinkage by 28%~55%, with smaller particle-sized biochar exhibiting superior internal curing performance. Furthermore, the internal curing water released by pre-wetted biochar improves cement hydration degree, promoting the formation of additional hydration products. This process not only enhances the densification of UHPC but also leads to marginal increases in 7 and 28 d compressive strength, thereby notably addressing the significant issue of compressive strength reduction in conventional internally cured UHPC.

Effect of Basalt Fiber on Interlayer Bonding Properties of 3D Printed Concrete

PEI Qiang, YANG Yuhang, ZHONG Yingzhu, QI Pengfei, ZHANG Luxi

2025, 44(7):  2465-2473.  doi:10.16552/j.cnki.issn1001-1625.2024.1280

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In this paper, the interlayer bonding properties of 3D printed concrete with basalt fiber were studied. The 3D printed concrete specimens with basalt fiber content of 0%, 0.3%, 0.6%, 0.9%, 1.2% and 1.5% (mass fraction) were designed and printed, respectively. The effects of basalt fiber on the macroscopic interlayer bonding properties of 3D printed concrete were analyzed by rheological properties, interlayer tensile and interlayer shear tests. The microstructure of 3D printed concrete with basalt fiber was analyzed by SEM and BET, and the influence of microstructure on the macroscopic interlayer bonding properties was discussed. The results show that compared with 3D printed concrete without basalt fiber, the rheological properties, interlayer tensile strength and interlayer shear strength of 3D printed concrete with basalt fiber are improved. The basalt fiber can bridge cracks in cement paste and inhibit the expansion of microcracks in the interface area. However, the high content of basalt fiber will lead to the increase of porosity of 3D printed concrete, thus reducing the interlayer bonding property. When the content of basalt fiber is 0.6%, the interlayer bonding property of 3D printed concrete is significantly improved, and its interlayer tensile strength and interlayer shear strength reach 3.51 MPa and 6.26 MPa, respectively.

Influence of Resonant Aggregates on Bandgap Region in Metaconcrete Cell

CHEN Junhao, CHEN Guodong, ZENG Xiaohui, LONG Guangcheng, XIE Youjun

2025, 44(7):  2474-2486.  doi:10.16552/j.cnki.issn1001-1625.2024.1398

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In this paper, a finite element model of the metaconcrete cell was established to analyze the effects of design parameters, including the shape, material parameters, geometric parameters, and material composition of the resonant aggregates, on the bandgap characteristics and regulation laws of the metaconcrete cell. The key design parameters were evaluated and discussed, and design principles of resonant aggregates were proposed. The results show that the bandgap region of the metaconcrete cell is influenced by the shape and orientation of the resonant aggregate. It is suggested that the spherical shape should be used as the resonant aggregate shape of the metamaterial cell. For the metaconcrete cell, achieving a low-frequency bandgap and wide bandgap cannot be accomplished solely by adjusting the elastic modulus and Poisson's ratio of the soft coating. The design principles should focus on reducing the elastic modulus and Poisson's ratio of the soft coating to obtain a low-frequency bandgap, and then adjusting the resonator density and resonant aggregate geometry parameters to achieve a wider bandgap range. For low-frequency vibration below 100 Hz, it is recommended to use polyurethane foam as the soft coating material and lead as resonator material. Furthermore, increasing the thickness of the soft coating is necessary to create a low-frequency bandgap, and increasing the filling rate of resonant aggregates is crucial for generating a wide bandgap.

Corrosion Inhibition of Rebar in Seawater-Sea Sand Concrete by MWCNTs/LDHs-NO₂

LING Weicheng, KE Guojun, JIN Dan, CHEN Shanqiu, DUAN Xiongkaibin

2025, 44(7):  2487-2494.  doi:10.16552/j.cnki.issn1001-1625.2024.1487

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A novel composite material—multi-walled carbon nanotube/nitrite intercalated layered double hydroxide composites (MWCNTs/LDHs-NO₂) was prepared using an electrostatic self-assembly method. The inhibitory effect of MWCNTs/LDHs-NO₂ on rebar corrosion in seawater-sea sand concrete under constant current accelerated corrosion was investigated through chloride ion adsorption experiments, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), rebar weight loss measurements. The results show that the composite of nitrite-intercalated layered double hydroxide and multi-walled carbon nanotubes effectively enhances the chloride ion adsorption capacity of the material, and its adsorption follows the Langmuir adsorption model, with a maximum adsorption capacity of 218.5 mg/g. Electrochemical testing reveals that the application of MWCNTs/LDHs-NO₂ in concrete can protect the passivation film of rebar, slowing down the corrosion process. After 12 d of accelerated corrosion by electric current, the weight loss rate of rebar in samples containing MWCNTs/LDHs-NO₂ is 62% lower compared to the samples without MWCNTs/LDHs-NO₂ added. Therefore, MWCNTs/LDHs-NO₂ can effectively enhance the corrosion resistance of rebar in concrete.

Impedance Performance of Concrete under Coupling Effect of Chloride Salts and Stray Currents

PENG Yuyi, ZHU Tiemei, HAN Guoqi, LYU Mengfan, ZHANG Xinyu, WANG Yan

2025, 44(7):  2495-2502.  doi:10.16552/j.cnki.issn1001-1625.2024.1437

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In order to investigate the variation law of impedance performance of concrete under the coupling effect of chloride salts and stray currents, the performance change of concrete for underground under the double erosion of chloride salts and stray currents was investigated by laboratory simulation method. The results show that the resistivity of concrete gradually decreases with the increase of erosion age. Chloride salts and stray currents coupled erosion significantly reduce the high frequency arc diameter of concrete. And the resistance of the unconnected conducting path of concrete under erosion tended to increase and then decrease, while the capacitance tended to decrease and then increase. The coupling effect of chloride salts and stray currents reduces the obstruction to harmful ion transport in concrete, accelerates steel corrosion, and thereby decreases concrete durability. This study can provide a scientific basis for the durability assessment and protection of metro concrete structures.

Fracture Property of PET Modified High DuctilityAlkali-Activated Concrete

LIANG Zhensheng, ZHANG Botao, LIANG Ruiqing, ZENG Junfeng, GUO Yongchang

2025, 44(7):  2503-2513.  doi:10.16552/j.cnki.issn1001-1625.2024.1472

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The use of polyethylene terephthalate (PET) powder as an aggregate in PET modified high ductility alkali-activated concrete (PHDAC) offers significant potential for advancing sustainable high-performance concrete materials. However, the fracture behavior of PHDAC remains unclear. This study investigated the effects of different PET powder volume replacement ratio (0%, 15%, 30% and 45%) quartz sand on the fracture property of PHDAC. Three-point bending tests were conducted to analyze failure modes, and the dual-K fracture model was used to evaluate crack initiation toughness Kⁱⁿⁱ_IC, instability toughness K^un_IC, and Mode Ⅰ fracture energy G_F. Scanning electron microscopy was employed to examine the material's microstructure, exploring the mechanisms by which PET powder influences fracture behavior. The results indicate that all PET-modified specimens exhibite ductile fracture characteristics, using 15% PET powder replacement quartz sand can significantly enhance Mode Ⅰ fracture energy of the material. Due to its hydrophobic property, PET powder forms a distinct interface transition zone (ITZ) with the slurry and other aggregates, this ITZ reduces interfacial density of the matrix interface, promotes matrix cracking, and makes the material more prone to multi crack cracking as a whole.

Solid Waste and Eco-Materials

Comparison and Optimization of Metakaolin Activity Determination Methods

YANG Kailu, YANG Dingyi, LU Shimin, CHEN Longxiang, MAO Xiang, ZHAO Jian

2025, 44(7):  2514-2527.  doi:10.16552/j.cnki.issn1001-1625.2024.1557

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Activity is a key index to evaluate the performance of metakaolin. The current activity determination methods are diverse, but there are problems such as time-consuming, inaccurate or unstable results. It is urgent to optimize them to achieve efficient and accurate determination method and promote the on-demand utilization of different active metakaolin. In this study, the activity index method, cement supernatant immersion method, pH value reduction rate method of saturated Ca(OH)₂ solution, pH value reduction rate method of heated saturated Ca(OH)₂ solution and diphenylguanidine adsorption rate method were used to determine the activity of different metakaolin. The methods were compared in terms of time-consuming, difficulty in operation, test repeatability and results accuracy. The results show that the pH value reduction rate method of heated saturated Ca(OH)₂ solution has a test repeatability of 0.988 87 and an accuracy of 0.926 26, making it a fast, simple and accurate method for determining activity of metakaolin.

Carbonation Corrosion Resistance of Circulating Fluidized Bed Ash-Slag

XIE Laikun, QIN Xiaohan, GUO Wenbin, ZHOU Mingkai

2025, 44(7):  2528-2537.  doi:10.16552/j.cnki.issn1001-1625.2025.0220

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Circulating fluidized bed (CFB) boiler fly ash and bottom slag contains a large number of sulfur-containing minerals, which hydrates to form ettringite when used in cement concrete, resulting in poor stability, thus restricting its large-scale application in cement concrete. In this paper, three kinds of CFB fly ash and CFB bottom slag were taken as research objects, CFB ash-slag test blocks were prepared by atmospheric pressure and medium temperature moisture retention methods, and the influence of carbonation corrosion on the compressive strength of CFB ash-slag test blocks was studied. The mechanism of carbonation corrosion resistance of CFB ash-slag test blocks was analyzed by XRD, TG-DTG and SEM tests. The results indicate that the compressive strength of CFB ash-slag test blocks decreases significantly after carbonation corrosion. XRD and TG-DTG test indicate that carbonation corrosion leads to the decomposition of hydration products ettringite in CFB ash-slag test blocks, producing calcium carbonate and calcium sulfate. SEM microstructure analysis shows that carbonation corrosion decomposes needle-rod ettringite in the cracks of test blocks, generating calcium carbonate. The ettringite originally filled in the crack gaps of CFB ash-slag test blocks is carbonized and decomposed, and the gaps are not filled with ettringite, resulting in a significant reduction in the compressive strength of test blocks. The related research reveals the carbonation corrosion resistance and mechanism of CFB ash-slag, and provides a theoretical basis for its resource utilization.

Effect of Activator on Rheological and Mechanical Properties of One-Part Lithium Slag-Based Geopolymer

ZHANG Zongyang, SHAMA Shibu, LUO Qi, LU Liulei, YE Weikai, SHENG Guodong, ZHANG Feng, DONG Faxin, LIU Mingwang, WANG Junfeng

2025, 44(7):  2538-2548.  doi:10.16552/j.cnki.issn1001-1625.2024.1602

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The preparation of lithium slag-based geopolymer is an efficient and low-carbon method for the utilization of lithium slag. Considering the significant influence of activator dosage on the performance of geopolymer, this study investigated the effect of activator dosage on the fluidity, setting time, rheological properties, and compressive strength of lithium slag-based geopolymer. The hydration process and microstructure of the lithium slag-based geopolymer were characterized through heat of reaction tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that increasing the activator dosage significantly reduces the workability of the geopolymer. Both the yield stress and plastic viscosity of the lithium slag-based geopolymer increase with increasing activator dosage. When the activator dosage is 3% (mass fraction), the 28 d compressive strength of the lithium slag-based geopolymer reaches a maximum of 35.9 MPa. An appropriate amount of activator promotes the polymerization reaction, generating more hydrated calcium (sodium) aluminosilicate (C(N)-A-S-H) composite gel, which effectively fills the pores and results in a denser geopolymer structure.

Effects of Fineness and Water-Binder Ratio on Carbon Mineralization Performance of Ladle Furnace Slag Carbon-Negative Binder

XIANG Weiheng, LIU Jun, HU Cheng, CHEN Ping, MA Xiaopeng, PENG Yingjie

2025, 44(7):  2549-2556.  doi:10.16552/j.cnki.issn1001-1625.2024.1628

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The low hydraulic activity of ladle furnace slag (LFS) is the limitation of utilization as the cementitious material. This study researched the effects of different fineness and water-binder ratios on carbonation activity of LFS and the compressive strength, mineral phase composition, and microstructure of carbonated samples. The results show that the CO₂ uptake and degree of carbonation is 17.16% and 39.6% respectively, and the compressive strength of carbonated samples is 213.03 MPa at a fineness of 777.8 m²/kg and a water-binder ratio of 0.100. The carbonation activity of LFS is significantly enhanced with the increase of fineness, but there is not an obvious increase when the fineness exceeds 642.6 m²/kg. And the increase of fineness results in a reduce of crystallinity of calcite generated by carbonation reaction, but promotes a considerable generation of carbonation products, which contributes to the improvement of compressive strength. With the increase of water-binder ratio, the carbonation activity of LFS and the compressive strength of carbonated samples are both foremost increased and then decreased. And at a water-binder ratio of 0.100, the amount of calcite generated in carbonation reaction is more, the crystal size of calcite is larger and the crystallinity of calcite is better.

Enhancement of Drying Shrinkage Resistance of Cement-Slag Based Foam Concrete by Calcium Sulfate

LIU Weicheng, WANG Qiong, CHEN Wei, ZENG Weilai, HUANG Mingyang, YUAN Bo

2025, 44(7):  2557-2565.  doi:10.16552/j.cnki.issn1001-1625.2024.1544

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Foam concrete has good heat insulation and sound insulation properties, but the drying shrinkage is large, and it is easy to crack in practical engineering applications. In this study, slag was used to replace part of cement. By adding anhydrous calcium sulfate to regulate the concentration of sulfate in slurry, the crystallization of ettringite was promoted to form transition structure, and the synergistic regulation of matrix compressive strength optimization and drying shrinkage reduction was realized. The results show that when the content of calcium sulfate is 1%~15% (mass fraction), the fluidity of foam concrete slurry increases first and then decreases with the increase of calcium sulfate content, and the settlement distance and drying shrinkage of foam concrete slurry increase first and then decrease with the increase of calcium sulfate content. When the content of calcium sulfate is 5%, compared with the control group, the fluidity of foam concrete slurry increases by 4.1%, the settlement distance of slurry at 90 min is the smallest (0.13 mm), the compressive strength at 28 d increases by 17.4%, and the drying shrinkage rate reduces by 28.0%. Appropriate amount of ettringite crystals can reduce the drying shrinkage by forming a transition structure, thereby reducing the cracking risk of foam concrete. This study provides a theoretical basis and technical path for the preparation of calcium sulfate used for anti-dry shrinkage foam concrete.

Performance of Engineered Cementitious Composites Prepared with Gold Tailing Sand as Fine Aggregate

YU Xin, WANG Long, HE Pingping, LIU Yusong

2025, 44(7):  2566-2577.  doi:10.16552/j.cnki.issn1001-1625.2025.0021

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Engineered cementitious composites (ECC) have attracted a lot of attention because of their high ductility. The preparation of ECC usually uses quartz sand with high cost and high carbon emission as fine aggregate, which makes ECC face the problems of environmental damage and high cost in practical engineering. In order to prepare ECC with lower cost and carbon emission, this study prepared ECC by replacing quartz sand with gold tailing sand, which is an industrial solid waste product. The flowability and mechanical properties of gold tailing sand based ECC and quartz sand based ECC under different water-cementitious material ratios and fly ash ratios were investigated. And the mechanical properties were explained by tests such as fracture toughness and fiber dispersion, so as to explore the feasibility of replacing quartz sand with gold tailings sand as fine aggregate to prepare low cost and low emission ECC. It is found that the flowability of ECC is negatively affected by the gold tailing sand with angular nature shape. However, in terms of mechanical properties, using gold tailing sand to prepare ECC can effectively improve its compressive and tensile strength, and achieve tensile strain performance comparable to quartz sand based ECC. Besides, the use of gold tailing sand to replace quartz sand in the preparation of low carbon ECC is feasible and helps to reduce the carbon emissions generated during the preparation of building materials.

Effects of ZnO Content and Firing Temperature on Properties of Lightweight Ceramsite and Mechanism Analysis

LI Boya, FAN Haihong, HE Yujie, WEI Kaibo, MA Chunling

2025, 44(7):  2578-2588.  doi:10.16552/j.cnki.issn1001-1625.2024.1518

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In this paper, coal gangue was used as the main raw material, steel slag as admixture, SiC as pore-forming agent, and ZnO as sintering aid to prepare ceramsite. The effects of ZnO content and firing temperature on the internal structure and properties of the prepared ceramsite were studied, and the mechanism of ZnO on the mineral phase change of the ceramsite was analyzed. The results show that with the increase of ZnO content and firing temperature, the skeleton structure of ceramsite becomes dense, the internal large pores gradually decrease, the small pores increase, and the water absorption decreases. The incorporation of 3% (mass fraction, the same below) and 4% ZnO can promote the formation of spinel phase in ceramsite and improve the strength of ceramsite. When the content of ZnO is 4% and the firing temperature is 1 170 ℃, the prepared ceramsite has the best performance, the water absorption is 6.74%, the bulk density is 420 kg/m³, and the cylinder compressive strength is 3.93 MPa.

Effect of Retarder on Performance of Slag-Red Mud Geopolymer

YUAN Hong, YANG Min, CAI Tingya, PAN Rongxiang

2025, 44(7):  2589-2596.  doi:10.16552/j.cnki.issn1001-1625.2024.1455

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Geopolymer as a new type of green low-carbon material, has attracted widespread attention due to its advantages such as high strength, short setting time, corrosion resistance, low carbon emissions, and environmental friendliness. However, the setting time of geopolymers is short, which is not conductive to construction in practical applications. To enhance the practical operability of geopolymer, this study selected sodium tripolyphosphate (STPP) and seignette salt (SS) as retarders. It investigated their effects on the setting time, fluidity, compressive strength, and flexural strength of slag-red mud geopolymer. Through methods such as X-ray diffraction (XRD), infrared spectrum (FT-IR), scanning electron microscope (SEM), and heat of hydration analysis, the study explored the impacts of retarders on the setting and hardening process of slag-red mud geopolymer. The results indicate that STPP and SS can both delay the hydration hardening of slag-red mud geopolymer. When the mass fraction of STPP and SS are both 7%, the compressive strength of the RG-STPP-7% sample at 28 d decreases by 1.8%, while the flexural strength decreases by 1.3%. In contrast, the 28 d compressive strength of the RG-STPP-7% sample decreases by 19.2%, and the flexural strength increases by 7.7%. Increasing the content of the retarder reduces the strength of geopolymer, with an optimal range of about 3%. STPP and SS primarily delay the setting and hardening rate of slag-red mud geopolymer gel materials through adsorption and complexation.

Effect of Alkali Residue Content on Properties of Solid Waste-Based Cementitious Materials

LI Zhiquan, ZHANG Guangtian, ZHANG Yanjia, JIA Biao, LIU Dongji, ZHANG Biao

2025, 44(7):  2597-2607.  doi:10.16552/j.cnki.issn1001-1625.2025.0015

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In this paper, alkali residue, slag, steel slag and desulfurization gypsum were used to prepare solid waste-based cementitious materials. The effect of alkali slag content on the standard consistency, setting time, fluidity and compressive strength of solid waste-based cementitious materials was investigated. The XRD, TG-DSC and SEM-EDS test methods were used to compare and analyze the hydration products and microstructure of cement and solid waste-based cementitious materials. The effect of alkali residue on the hydration products and microstructure of solid waste-based cementitious materials was investigated. The results show that the alkali residue can increase the standard consistency of cementitious materials and reduce the fluidity. The optimum content of alkali residue is 15% (mass fraction). At this time, the standard consistency of cementitious materials is 28.4%, the initial setting time is 292 min, the final setting time is 359 min, the 1 d compressive strength is 7.1 MPa, the 3 d compressive strength is 27.4 MPa, the 7 d compressive strength is 36.4 MPa and the 28 d compressive strength is 49.6 MPa. The chloride and sulfate in alkali residue can accelerate the early hydration reaction process of cementitious materials, and generate more Friedel's salt, ettringite (AFt) and calcium aluminosilicate hydrate (C-(A)-S-H) gel, so that the early strength is improved. The later hydration products are continuously generated, interspersed and overlapped to form a dense structure, which ensures the later strength growth of cementitious materials.

Ceramics

Research and Application of Lignin Depolymerisation Products Modified Melamine-Based Ceramic Additives

CHEN Tao, LI Siyu, ZENG Qibin, LIU Yifan, LIU Minghua

2025, 44(7):  2608-2616.  doi:10.16552/j.cnki.issn1001-1625.2024.1615

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To address the high production cost and poor storage stability of traditional melamine (SMF) ceramic additives, lignin depolymerisation products were used as raw materials to prepare lignin depolymerisation products modified melamine (SLMF) ceramic additives through a four-step method. Single-factor experiments were conducted to optimize the preparation conditions. Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, gel permeation chromatography were used to characterize the structure and properties of materials. The results show that SLMF successful introduces lignin structure and its thermal stability is significantly better than that of SMF. Application performance tests demonstrate that SLMF achieves excellent results at 0.5% (mass fraction) addition and a ball milling time of 6 min, and ceramic slurry exhibits excellent performance: outflow time is 17.45 s, viscosity is 2.57×10^-2 Pa·s, thickening rate is 1.25, average particle size is 1 011.35 nm, and green body flexural strength reaches 2.95 MPa. Compared to SMF, SLMF shows significant improvements in grinding aid, dispersing, and strengthening properties. Microstructure and XRD analyses reveal that SLMF effectively reduces particle size, decreases voids, improves green body density, and enhances crystallinity, resulting in higher green body strength. Compared with commercial additives, SLMF demonstrates superior overall performance and promising application potential.

Properties of Thermal Insulation Foam Ceramics Prepared by Asbestos Tailings and Coal Fly Ash

YANG Jin, SUN Hongjuan, PENG Tongjiang, LUO Liming, CHEN Shize

2025, 44(7):  2617-2629.  doi:10.16552/j.cnki.issn1001-1625.2024.1534

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In order to realize the high value-added utilization of solid waste, enstatite-cordierite based thermal insulation foam ceramics (foam ceramics) were successfully prepared by spontaneous foaming process with asbestos tailings and coal fly ash as main raw materials and quartz sand as auxiliary materials. The influences of sintering temperatures and quartz sand content on the pore structure, physical properties, and thermal conductivity of foam ceramics were investigated. The results show that the thermal conductivity of foam ceramics is mainly affected by pore structure and distribution. With the increase of quartz sand content and sintering temperature, the porosity of foam ceramics increases gradually, and the pores change from uneven distribution to uniform distribution of closed pore structure. The existence of low thermal conductivity gas in the pores effectively inhibits the heat conduction. At the same time, the increase of quartz sand content promotes the increase of the relative content of low thermal conductivity crystal phase (such as cordierite), while the relative content of high thermal conductivity crystal phase (such as spinel) decreases, thus further reducing the thermal conductivity. The thermal conductivity of the prepared foam ceramics at room temperature can reach a minimum of 0.17 W/(m·K), the porosity reaches 69.43%, and the compressive strength is 18.77 MPa, which is better than the requirements of the "General code for energy efficiency and renewable energy application in buildings" (GB 55015—2021) for building exterior wall insulation materials. This paper presents experimental basis for the resource utilization of asbestos tailings and coal fly ash, and provides theoretical support and practical references for improving the performance of energy-efficient building materials, with significant environmental advantages and application potential.

Effect of Low-Crystallinity BN Coating on Properties of Continuous Si₃N₄ Fiber

CUI Bingxia, JIANG Yuanqiang, WANG Han, CAI Wuji, HUANG Xiangxian, ZHANG Andong, WANG Xinbin

2025, 44(7):  2630-2637.  doi:10.16552/j.cnki.issn1001-1625.2024.1605

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BN coating was deposited on the surface of continuous Si₃N₄ fiber by chemical vapor deposition (CVD). The phase composition and microstructure of the fibers and BN coating were analyzed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The effect of BN coating on the monofilament tensile strength of Si₃N₄ fibers was evaluated by the Weibull distribution method. The results show that the BN coating on Si₃N₄ fiber has a low-crystallinity structure with a B/N atomic ratio close to 1∶1. After deposition, the monofilament tensile strength distribution deviates from a normal distribution, and the strength dispersion increases. With increasing heat treatment temperature, the BN coating transforms into borosilicate glass, inhibiting the expansion of pore size and volume within the fiber. The strength of BN-coated fibers declines slowly with temperature and remains higher than that of uncoated fibers at 1 400~1 500 ℃.

Glass

Effect of CeO₂ Doping on Structure, Optical and Mechanical Properties of Bi₂O₃-B₂O₃-ZnO Glass Coatings

SHAO Minglu, SHI Wangming, ZHANG Liang, LUO Lida, WANG Qingwei

2025, 44(7):  2638-2646.  doi:10.16552/j.cnki.issn1001-1625.2025.0019

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In order to improve the shielding range of Bi₂O₃-B₂O₃-ZnO glass coating in long-wave ultraviolet, and increase its surface hardness and modulus to achieve better protective effect, CeO₂ doped Bi₂O₃-B₂O₃-ZnO glass coating was prepared. The surface morphology of the coating was evaluated by DSC, SEM, Raman, FTIR, XPS and other test methods. The effects of different CeO₂ doping concentrations on the structure, optical and mechanical properties of Bi₂O₃-B₂O₃-ZnO glass coating were studied. The results show that when the doping concentration of CeO₂ is 0%~1.0% (molar fraction), the microhardness of coating reaches 6.9 GPa and the modulus reaches 84.0 GPa. When the CeO₂ doping concentration is 1.0%~2.5%, the polarization of Ce⁴⁺ and Ce³⁺ contained in CeO₂ reduces the microhardness and modulus of coating. At the same time, due to the change of glass structure, the conversion between Ce⁴⁺ and Ce³⁺ is promoted, and the ultraviolet shielding band of coatings with different CeO₂ doping concentrations is significantly different.

Effects of B₂O₃ and Al₂O₃ on Glass Network Structure, Thermal Properties,and Thermal Safe Performance of Borosilicate Glass

SHAN Chuanli, KE Zhenkun, HAO Mengyao, SHI Lifen, WANG Pingping, NI Jia

2025, 44(7):  2647-2655.  doi:10.16552/j.cnki.issn1001-1625.2024.0974

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The adjustment of B₂O₃ and Al₂O₃ content in borosilicate glass has a significant effect on the thermal properties and thermal safe performance of glass. In this paper, the effects of B₂O₃ and Al₂O₃ on the network structure, thermal properties and thermal safe performance of borosilicate glass (SiO₂-Na₂O-B₂O₃-CaO-Al₂O₃) were systematically studied, which provided a reference for the further optimization of the fire resistance of borosilicate glass. The results show that the interconnection between borate and silicate network decreases with the increase of B/Si molar ratio, which is caused by the decrease of the number of Si—O—B mixed bonds. With the increase of Al/Si molar ratio, the interconnection between borate and silicate network decreases, the thermal shock resistance value ΔT of borosilicate glass decreases gradually, the coefficient of thermal expansion α increases gradually, and the fire resistance of borosilicate glass decreases gradually. The borosilicate glass (82.7% SiO₂, 12.2% B₂O₃, 4.0% Na₂O, 1.1% CaO, all in molar fraction) has the best thermal properties and thermal safe performance, its α=3.33×10^-6℃^-1, ΔT=205 ℃, and it still has integrity after 20 min fire resistance test.

Effects of Feed Rate and Stability on Bubbling of Plasma Melting Quartz Glass

SUN Pengbo, SONG Xuefu, SUN Yuancheng, WANG Lei, DU Xiurong, ZHANG Xiaoqiang, LIU Xing, ZHOU Lisheng, YU Xinmin

2025, 44(7):  2656-2662.  doi:10.16552/j.cnki.issn1001-1625.2025.0070

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Bubble defects arising from improper feed rate control during the melting process is one of the important factors leading to the significant reduction of optical properties and mechanical strength of quartz glass. The effects of different combinations of layer thickness and feed rate on the stability of feed rate by using the sum of squares of residuals as an evaluation index were investigated, and the effect of feed rate on the formation of bubble defects during the preparation of quartz glass by plasma melting was deeply analyzed. The results show that the stability of material velocity is optimal when the layer thickness is 6.0 mm. The number of bubbles in quartz glass increases with the increase of feeding rate from 2.0 to 6.0 kg/h. Under low feed rate (2.0 kg/h), the total amount of quartz sand is small, the energy supply is sufficient to promote the full melting of raw materials and the melt has fewer bubbles and high temperature. High temperature reduces the viscosity of the melt, accelerates the movement of bubbles and promotes their merger and growth. High feed rate (6.0 kg/h) shortens the growth time of bubbles, inhibits the merger of bubbles, and promotes the homogeneous dispersion of gases in melt, resulting in an increase in the number of gas bubbles but decrease in size.

Preparation and Luminescent Properties of Tb Doped Zeolite Derived Transparent Glass

SI Hai, SA Churonggui, DAI Wurihan, SUN Yong, BAO Wujisiguleng

2025, 44(7):  2663-2669.  doi:10.16552/j.cnki.issn1001-1625.2024.1589

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Rare earth ions doped zeolite derived glass materials have the advantages of adjustable composition, straightforward preparation, low cost and effective luminescence properties. In this study, high concentration terbium (Tb) doped zeolite A (LTA) derived transparent glass was prepared by the melt-quenching method under a sintering temperature of 1 300 ℃. The structure and luminescence properties of the samples were characterized by XRD and fluorescence spectroscopy. The results show that the concentration quenching value for Tb ions in the sample is increased to 24.9% (mole fraction) of Si⁴⁺ (doping concentration of 14%, mass fraction) and the transmittance of the glass reaches 91%. The glasses show strong green luminescence under excitation of 486 nm. The luminescence intensity and transmittance of the glass can be adjusted by varying the Tb concentration. The luminescent properties of Tb doped zeolite derived glass materials are influenced not only by the concentration of Tb but also by the glass structure. The glass has potential applications in the fields of high-transparency solid-state illumination, green light sources.

Refractory Materials

Corrosion Behavior of Al₂O₃-MgAl₂O₄ Refractory for Copper Smelting Furnace

LIU Wei, WEI Yinghui, LI Yuwen, ZHANG Jianyu, CHAI Shengli

2025, 44(7):  2670-2679.  doi:10.16552/j.cnki.issn1001-1625.2025.0074

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The lifetime of refractory materials is critical for copper melting furnaces. In response to the leakage alarms at the slag-melt interface, the chemical reactions occurring among slag, melt and refractory were first simulated. Subsequently, the elemental distribution and phase composition of refractory eroded areas were analyzed, progressing from the hot face to the cold face. The results show that complex chemical reactions occur between refractory used in copper melting furnace (with Al₂O₃ and MgAl₂O₄ as main phases) and slag (containing C, Cu₂O, Cu, SiO₂, FePO₄, Ca₃(PO₄)₂, etc). Four distinct corrosion zones are formed from the hot face to the cold face: the slag adherence zone (where Cu/FePO₄ liquid phase bind with solid components), the reaction zone (where refractory coexists with reaction products such as Cu/FePO₄ liquid phases, MgSiO₄ and AlPO₄), the copper infiltration zone (where Cu liquid penetrates refractory) and the unreacted zone (original refractory). Based on the corrosion mechanism, improvement strategies are proposed, including controlling the content of externally introduced impurity elements (such as Fe, Ca, Si), optimizing the furnace dismantling and startup processes to reduce lining defects, increasing the TiO₂ content, and avoiding mechanical damage to the lining. This study provides industrial recommendations for extending the lifetime of copper smelting furnace.

Functional Materials

Research Progress of Metal-Organic Framework Derivatives in the Field of Energy Storage

YU Jiahui, HE Ke, LI Mengyu, YANG Zhiguang, CHEN Qianqian, FAN Bingbing

2025, 44(7):  2680-2692.  doi:10.16552/j.cnki.issn1001-1625.2025.0017

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The growth of energy storage demand and the importance of environmental protection promote the development of efficient and sustainable energy storage technology. Metal-organic framework (MOF) derivatives are widely used as energy storage materials such as electrode materials, electrocatalysts and battery separators because of their high porosity, low density, large specific surface area, regular and adjustable pore size, topological diversity and cuttability. By using different synthesis methods, different types of MOF materials are synthesized and their structures are changed to improve energy efficiency. In this paper, the types of common MOF derivatives and their applications in energy storage fields such as metal batteries, lithium-sulfur batteries, supercapacitors and solar cells are reviewed, the problems and challenges faced by MOF derivatives are put forward, and the sustainable development of MOF derivatives in the future energy storage field is prospected.

Design and Performance Optimization of High-Entropy Perovskite La_0.7Sr_0.3Co_0.4Fe_0.1Ni_0.4Cu_0.1O₃ Supercapacitor Electrode Materials

ZHANG Yaxin, LUO Dongqing, WANG Feifei, LYU Jingbo, QIN Zengming

2025, 44(7):  2693-2700.  doi:10.16552/j.cnki.issn1001-1625.2024.1532

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High-entropy perovskite oxides are promising electrode materials for supercapacitors due to their excellent structural stability and chemical diversity. In this study, the high-entropy perovskite materials La_0.7Sr_0.3Co_0.4Fe_0.1Ni_xCu_0.5-xO₃(x=0.1, 0.4) were synthesized using the sol-gel method to investigate the effects of varying Ni and Cu molar ratios on the material structure and electrochemical performance. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The results indicate that La_0.7Sr_0.3Co_0.4Fe_0.1Ni_0.4Cu_0.1O₃ exhibits a cubic perovskite structure with small, uniformly distributed grains and a high oxygen vacancy content. Electrochemical testing in the 3 mol/L KOH electrolyte demonstrats that La_0.7Sr_0.3Co_0.4Fe_0.1Ni_0.4Cu_0.1O₃ achieves the specific capacity of 243 F·g^-1 at the current density of 1 A·g^-1, which is 42% higher than conventional LaFeO₃ materials. After 20 000 charge-discharge cycles (current density is 5 A·g^-1), the materials retain 98.3% of their initial specific capacity, demonstrating excellent cycling stability and long cycle life. High-entropy perovskite materials have outstanding electrochemical performance and have application potential as high-performance energy storage materials.

Modulation of Built-In Electric Field in Bi₄NbO₈Cl Through Thickness Thinning to Enhance Photocatalytic Performance

LIU Tong, HUANG Shimou, HAO Enqiang, CAO Yuxi, ZHU Congcong

2025, 44(7):  2701-2709.  doi:10.16552/j.cnki.issn1001-1625.2025.0153

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The low separation rate and high recombination rate of photogenerated carriers are important reasons limiting the photocatalytic efficiency. Utilizing the built-in electric field of ferroelectrics as an additional driving force is a feasible solution to improve the separation efficiency of photogenerated carriers. In this paper, the typical bismuth-based ferroelectric semiconductor Bi₄NbO₈Cl was selected as a model system. Leveraging the thickness-dependent increase of the built-in electric field and circumventing the diminished photocatalytic activity caused by nanosheet stacking, a three-dimensional (3D) nano-interconnected architecture composed of Bi₄NbO₈Cl ultrathin nanosheets was constructed. By reducing the lamellar thickness, the internal electric field of Bi₄NbO₈Cl is enhanced, thus driving more efficient separation of photogenerated carriers. The effects of the enhancement of the built-in electric field on the separation, transfer and recombination processes of photogenerated carriers are analyzed through photoelectrochemical tests. Furthermore, the underlying mechanism by which the built-in electric field intensifies as the layer thickness thins is systematically investigated. Finally, the photocatalytic degradation experiment of bisphenol A shows that the photocatalytic efficiency of the three-dimensional nano-crosslinked structure is enhanced by 2.41 times. This work provides a new perspective for in-depth understanding of the action mechanism of the built-in electric field on the separation of photogenerated carriers.

Road Materials

Effects of Water-Reducing Agents on Rheological Property and Strength of Magnesium Slag-Fly Ash-Based Flowable Solidified Soil

HAO Mingsheng, QIN Qingjin, GAO Hui, QU Chunyu, QIN Yong,FANG Kuizhen, HAO Jianshuai

2025, 44(7):  2710-2719.  doi:10.16552/j.cnki.issn1001-1625.2024.1582

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In this study, the effects of polycarboxylic acid (PCE) content, melamine (SM) content and naphthalene (NF) water-reducing agent content on the rheological properties and compressive strength of magnesium slag-fly ash based flowable solidified soil were discussed. Through fluidity test, rheological properties analysis and compressive strength evaluation, the mechanism of action of the type and content of water-reducing agent on the fluidity, yield stress, plastic viscosity, apparent viscosity, thixotropy and compressive strength of flowable solidified soil was discussed. The results show that the three types of water-reducing agents can improve the fluidity and rheological properties of flowable solidified soil. The effects of SM and NF water-reducing agents are significant, and the effect of PCE water-reducing agent is relatively weak. When the water-reducing agent content is 1%(mass fraction), the fluidity of flowable solidified soil with SM and NF water-reducing agent increases by 25% and 37%, respectively. The addition of water-reducing agent significantly reduces the yield stress, plastic viscosity and thixotropy of paste, especially NF and SM water-reducing agent, which has a strong particle dispersion effect and can effectively reduce the aggregation and flocculation between particles. The fluidity of flowable solidified soil is negatively correlated with yield stress, and reducing yield stress is the key to improve fluidity. Appropriate addition of SM water-reducing agent can improve the full-age compressive strength of flowable solidified soil, enhance the uniformity and compactness of material, while NF water-reducing agent will have an adverse effect on the compressive strength.

Frost Resistance of Recycled Tire Polymer Fiber Cement Modified Carbonated Saline Soil

WANG Jiahui, WANG Fengchi, SUN Chang

2025, 44(7):  2720-2729.  doi:10.16552/j.cnki.issn1001-1625.2024.1598

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Adding recycled tire polymer fiber (RTPF) to carbonated saline soil can enhance its shear performance. Additionally, the utilization of RTPF enables resource recycling and reuse while significantly reduces the environmental burden. For the saline soil in seasonally frozen regions, this study investigated the shear strength damage law of RTPF cement modified carbonated saline soil under freeze-thaw cycles through laboratory experiments. Triaxial shear tests were conducted on modified carbonated saline soil by different RTPF content after freeze-thaw cycles. The results indicate that the stress-strain curves of RTPF modified carbonated saline soil exhibit strain softening characteristics, and RTPF can improve the elastic modulus of cement modified carbonate saline soil. RTPF can enhance the breaking strength of cement modified carbonated saline soil, with the 1.0% (mass fraction) RTPF bunch is the most significant improvement. RTPF improves the frost resistance, and the effect of RTPF bunch on enhancing the frost resistance is more significant. The modified carbonated saline soil demonstrates higher cohesion after adding RTPF, and the cohesion gradually decreases with the increase number of freeze-thaw cycles. The number of freeze-thaw cycles has no obvious effect on internal friction angle, showing no clear trend. RTPF plays a bridging effect, limits the micro fracture development and enhances the stability of modified carbonated saline soil.

Synergistic Solidification of Red Sandstone Soil by Industrial Solid Waste

YAO Juntian, YANG Jianyu, YANG Weijun, JIN Zhenzhou, HE Zhihui, HE Jiangang

2025, 44(7):  2730-2740.  doi:10.16552/j.cnki.issn1001-1625.2024.1600

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In order to improve the characteristics of red sandstone soil, which is easy to soften and disintegrate after water or disturbance, and its physical properties decrease sharply, the red sandstone soil was solidified by alkali-activated mineral powder and hemihydrate gypsum. The orthogonal test was used to analyze the influence of each component on the 7 d unconfined compressive strength and water stability of the solidified red sandstone soil, and the drying-wetting cycle resistance and micro-characteristics of the solidified red sandstone soil were studied. The results show that the effect of hemihydrate gypsum on the 7 d unconfined compressive strength of solidified soil is the most significant, and the effect of mineral powder on water stability is the most significant. When the dosage of the solidified agent is 20% (mass fraction), the 7 d unconfined compressive strength of the solidified soil reaches 2.45 MPa, the water stability coefficient reaches 0.92, and the performance after 28 d is superior to that of traditional cement curing agents.The microscopic tests show that the bonding and filling of the intergranular pores of red sandstone soil by calcium silicate aluminosilicate hydrate (C-A-S-H) and ettringite (AFt) generated by alkali-excited mineral powder is the main reason for the improvement of the 7 d unconfined compressive strength and water stability coefficient of the red sandstone soil after solidification. This research provides a solution to the solidification problem of red sandstone soil.