Table of Content

Volume 44 Issue 2
15 February 2025

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Cement and Concrete

Influence Mechanism of Compounding Calcium Aluminate Cement and Wollastonite on Corrosion Resistance of Magnesium Potassium Phosphate Cement

BAI Liang, LI Yuanhang, WANG Xin, ZHENG Hui, LIANG Xingwen

2025, 44(2):  393-402.  doi:10.16552/j.cnki.issn1001-1625.20241118.005

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In order to explorecalcium aluminate cement (CAC) and wollastonite (WS) synergistic modification effect, 13 groups of modified magnesium potassium phosphate cement (MKPC) specimens with different mix ratios were designed by compounding CAC and WS in this paper. The corrosion resistance and microscopic characteristics of modified MKPC under the action of NaCl, MgSO₄, NaOH and H₂SO₄ solutions were studied. The results show that the reaction product of CAC is coated on the MKPC hydration product magnesium potassium phosphate hexahydrate (MgKPO₄·6H₂O) in the form of amorphous aluminum gel and fill in the pores between MgKPO₄·6H₂O crystals, which improves the microstructure of MKPC and inhibits the corrosion of corrosive media. As an inert component, WS does not participate in hydration reaction of MKPC, but makes the pore structure of MKPC denser by filling. The synergistic effect of CAC and WS can effectively improve the corrosion resistance of MKPC in NaCl and MgSO₄ solutions. When the content of CAC and WS is 15% and 5% of the mass of cementitious material, the improvement effect is the best. In NaOH and H₂SO₄ solutions, the CAC reaction products filled between MgKPO₄·6H₂O crystals are corroded, resulting in the formation of interconnected channels between crystals, which affects the improvement of corrosion resistance.

Effect of Ferrous Gluconate on Properties of Magnesium Oxychloride Cement

WANG Bo, HUANG Tao, CHEN Ruijie, QI Zefeng, SONG Zijian, JIANG Linhua, CHU Hongqiang

2025, 44(2):  403-416.  doi:10.16552/j.cnki.issn1001-1625.2024.0988

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This study explored the enhancement of magnesium oxychloride cement (MOC) properties by ferrous gluconate, including compressive strength, water resistance and degradability. In experiments, ferrous gluconate was added to MOC at varying proportion from 0.2% to 0.8% (mass fraction). The results show that 0.2% ferrous gluconate increases the 14 d compressive strength of MOC to (78.14±1.32) MPa, which is 19.3% higher than that of the control group. Additionally, the modified MOC demonstrates a higher 7 d softening coefficient (0.59) in water resistance tests, superior to that of the unmodified sample (0.29). At the dosage of 0.8% ferrous gluconate, the yield stress and plastic viscosity of MOC paste are reduced by 9.118 Pa and 0.112 Pa·s, respectively. The modified MOC has better fluidity and is convenient for practical application operation and control. These results confirm the significant potential of ferrous gluconate in enhancing the compressive strength, water resistance, and regulating the degradability of MOC.

Effect of Flowing Water Scouring on Mechanical Properties of Cement Grouting Materials

WANG Hongliang, LUO Ran, LIU Xiqi, LEI Lele, WENG Lei, WU Longji

2025, 44(2):  417-423.  doi:10.16552/j.cnki.issn1001-1625.2024.1106

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In order to study the effect of flowing water scouring on the mechanical properties of cement grouting materials, uniaxial compression tests were carried out on residual grout stone body after flowing water scouring. The microstructure of stone body was characterized by nuclear magnetic resonance and scanning electron microscopy. The effect mechanism of flowing water scouring on the mechanical properties of cement grouting materials was discussed in combination with microstructure. The results show that the uniaxial compressive strength and elastic modulus of grouting material decrease significantly due to flowing water scouring, and the attenuation degree becomes more significant with the increase of water flow velocity. At the same time, the peak strain and ultimate strain of residual grout stone body are reduced. When the water flow velocity reaches 1.0 m/s, the residual grout stone body shows obvious brittle failure characteristics. In addition, the number of micropores in residual grout stone body increases significantly, which is the main reason for the attenuation of its mechanical properties. This study is helpful to understand the real mechanical properties of grouting materials in flowing water scouring environment.

Influences of Metamaterials on Bending Toughness of Cement-Based Materials Based on Acoustic Emission Parameters

ZHU Guiwang, QIN Lei, DING Weijian, LI Pingfeng, SUN Ming

2025, 44(2):  424-433.  doi:10.16552/j.cnki.issn1001-1625.20241113.001

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To investigate the feasibility of using novel reinforcing materials to replace fibers to improve the bending toughness of concrete, this study used 3D printing of polylactic acid (PLA) to prepare metamaterials and embedded them into cement-based materials. The crack evolution and mechanical properties of metamaterials and polypropylene (PP) fibers under bending load were studied by using three-point bending and acoustic emission measurement technology. The fracture behavior of metamaterials and PP fibers and the effects of metamaterials on the bending toughness of cement-based materials were analyzed from a microscopic perspective. The results show that the flexural strength of specimen embedded with metamaterials is 40.4% higher than that of specimen with PP fibers, and 116.8% higher than that of control group. Metamaterials greatly enhance the flexural strength of cement-based materials, changing the failure mode from a single crack mode to multiple crack modes, and brittle failure to plastic failure. PP fibers only increase the flexural strength of cement-based materials. The proportion of tensile cracks in the stable growth stage and instable cracking stage of metamaterials is significantly higher than that of PP fibers, and the toughness index is 16.75 times and 4.37 times that of PP fibers.

Mechanical Properties and Damage Constitutive Models of Sawdust-Magnesium Oxychloride Cement Composite

FENG Peiyang, FANG Qiang, ZHANG Huagang, YU Tao, YANG Jiaojiao, NING Pan

2025, 44(2):  434-446.  doi:10.16552/j.cnki.issn1001-1625.2024.1017

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Sawdust-magnesium oxychloride cement composite (SMOCC) is a kind of new building material incorporating magnesium oxychloride cement as cementitious material, sawdust as filling material, mixed with appropriate proportion of modifiers, and pressed and molded under 5 MPa pressure. In order to investigate the basic mechanical properties and damage evolution of SMOCC, cubic compression, cubic split tensile and prism compression tests at different loading rates were carried out. At the same time, based on the experimental results, the statistical damage constitutive models of SMOCC under different loading rates were established by using Lognormal and GaussAmp statistical distribution functions, respectively, combined with the equivalent strain principle. The results show that the cubic compressive strength, splitting tensile strength, and elastic modulus increase with the increase of apparent density. The peak strain and peak stress of SMOCC decrease with the increase of loading rate. At lower loading rates, the internal defects and micro-cracks of SMOCC develop more fully, the concave of the initial compaction section of the stress-strain curve is more obvious, and the brittle failure of the material is improved. Compared with the Lognormal statistical distribution function, the constitutive model established by the GaussAmp statistical distribution function is able to better describe the uniaxial compressive mechanical behavior and damage evolution process of SMOCC. The research results can provide a theoretical basis for the design and application of SMOCC.

Mechanical Strength and Damage Mechanism of Rubber Concrete with Supplementary Cementitious Materials after High-Temperature

ZHOU Bowen, ZHENG Zezhong, MA Qiankun, HUANG Wenjie, ZHANG Zhiyun, ZHANG Jicheng

2025, 44(2):  447-454.  doi:10.16552/j.cnki.issn1001-1625.20241202.001

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In order to explore the mechanical strength degradation characteristics of rubber concrete (RC) after high-temperature, the mass loss, compressive strength, splitting tensile strength and flexural strength of RC with different supplementary cementitious materials (SCMs) under high-temperature were tested, and the effects of temperature and SCMs on RC strength were analyzed. The results indicate that as the temperature increases, the color of RC specimens gradually lightens from dark to light, accompanied by varying degrees of cracking, spalling, and mass loss, with severe deterioration occurring at 800 ℃. The mass loss rate of RC peak at 700 ℃. Rubber particles and SCMs improve the failure mode of RC and enhance residual strength before 200 ℃, but mechanical strength of RC sharply declines after 400 ℃. Scanning electron microscopy analysis reveals that high-temperature leads to the increase of internal pores and cracks in RC, and the deterioration of the microstructure is the main cause for the degradation of macroscopic mechanical strength of RC. Based on the experimental data, functional formulas have been established between temperature and the loss rates of cubic compressive strength, splitting tensile strength, and flexural strength, providing theoretical support for the study of high-temperature performance of RC.

Effect of Ramie Fiber on Mechanical Strength of Recycled Aggregate Concrete

YAN Jie, XING Guobin, FENG Longhui, LIANG Chongyang, XIE Jun, WENG Weisu, BAI Qijing

2025, 44(2):  455-462.  doi:10.16552/j.cnki.issn1001-1625.2024.1060

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In order to improve the mechanical properties of recycled aggregate concrete (RAC), ramie fiber (RF) was added into the concrete. The effects of recycled coarse aggregate (RCA) and RF on compressive strength, flexural strength and splitting strength of concrete were studied. The effects of RF on concrete properties and the improvement mechanism were further explored through nitrogen adsorption method and scanning electron microscope analysis. The mechanical properties of recycled aggregate concrete firstly increase and then decrease with the increase of RF content. When the replacement rate of RCA is 30% (mass fraction), the bending strength and splitting strength of the concrete with 0.5% (volume fraction) RF is 11.5% higher than that without RF. It can be seen from the microscopic analysis that the high water absorption rate of RF can make the cement paste on the fiber surface produce hydration reaction, and the generated hydrated calcium silicate gel fills the pores and thus increases the compressive strength of concrete. However, RF is prone to agglomerate when mixing concrete, forming weak areas, increasing internal defects, and inhibiting the improvement of compressive strength. The addition of RF has a relatively small effect on the improvement of compressive strength of concrete. RF surface is rough and has vertical stripes, which increases the bond strength of both sides of concrete cracks, acts as a bridge on both sides of concrete cracks, limits the development of concrete cracks under tensile load, and can greatly improve the flexural and splitting strength of concrete.

Experimental Study on Interfacial Bonding Performance Between Engineered Geopolymer Composites with Hybrid PE/PVA Fiber and Concrete

CHU Lijing, ZHUO Kexian, YANG Zeming, LI Chaosen, LIU Run’an, LIN Jiaxiang

2025, 44(2):  463-473.  doi:10.16552/j.cnki.issn1001-1625.2024.1020

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Engineered geopolymer composites (EGC) exhibit excellent tensile ductility and crack control capabilities, making it promising materials for concrete structure repair. However, EGC high cost and the lack of understanding regarding the bonding mechanisms between EGC and concrete have limited EGC widespread application. By using polyethylene (PE) fiber and domestically produced polyvinyl alcohol (PVA) fiber, hybrid PE/PVA fiber EGC (PE/PVA-EGC) were prepared and the bonding performance at EGC-concrete interface was investigated. Slant shear tests were conducted to explore the effect mechanisms of varying PE fiber content, hybrid PE/PVA fiber ratio, and precursor ratio on the interfacial bonding performance. Results indicate that increasing PE fiber content, PVA fiber replacement ratio, ground granulated blast furnace slag content and concrete strength can improve the interfacial shear bonding strength. Increasing the PE fiber content from 1.0% (volume fraction) to 2.0% improves the interfacial shear bonding strength of specimens by 13.24%. The interfacial shear bonding strength increases with higher replacement ratio of PVA fiber and the strength of matrix. The best bonding performance is observed when the existing concrete strength grade is C50. In conclusion, with an appropriate matrix strength, hybrid PE/PVA fiber can effectively enhance the interfacial bonding performance between EGC and existing concrete while controlling repair or reinforcement costs.

Study on Improvement of Concrete Resistance to Ammonium Sulfate Corrosion in Coastal Environment

TAN Jie, HU Wei, LIU Yang

2025, 44(2):  474-489.  doi:10.16552/j.cnki.issn1001-1625.2024.0991

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To address the problem of insufficient durability of concrete in ammonium sulfate environments in coastal areas, this study systematically evaluated the durability of concrete under ammonium sulfate infiltration using different water-cement ratios (w/b) and surface coating treatments. The concrete specimens were coated with colloidal silicate, silane/nanocomposite, and vinyl ester/nanocomposite coatings, and the mass change, and microstructural evolution were tested under baseline infiltration and composite infiltration (freeze-thaw cycle and dry-wet cycle) condition. The results show that composite infiltration caused more serious damage to concrete than baseline infiltration. After reducing the water-cement ratio from 0.6 to 0.4, the cumulative mass loss of the concrete specimens coated with pure vinyl ester is reduced by about 55% compared with the uncoated specimens. Reducing the water-cement ratio densifies the microstructure of concrete and reduces permeability. Although the colloidal silicate surface treatment improved the initial fluid resistance, it failes to effectively protect the concrete due to its hydrophilicity and the shrinkage microcracks of the coating. When the water-cement ratio is 0.6, the cumulative mass loss of the concrete specimen with the silane/nanocomposite coating can be reduced by up to 56% compared with the specimen coated with pure silane due to its hydrophobicity and the enhancement effect of the nanomaterial.When the water-cement ratio is 0.4, the cumulative mass loss of the concrete specimens coated with vinyl ester/nanocomposite can be reduced by up to 65% relative to the specimens coated with pure vinyl ester due to the strong bond and chemical stability of the polymer film. Both silane and vinyl ester nanocomposites show good results in the protection of concrete from ammonium sulfate corrosion in coastal areas, providing effective protective measures for the design and maintenance of concrete structures in coastal areas, which can significantly extend the service life of concrete structures in ammonium sulfate environments and reduce maintenance and replacement costs.

Solid Waste and Eco-Materials

Research Status and Progress on Solidifying Soft Clay by Geopolymer

JIA Rui, CHU Zhenxing

2025, 44(2):  490-500.  doi:10.16552/j.cnki.issn1001-1625.2024.1105

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The geopolymer is considered to be a green cementitious material that likely to substantially replace cement in the 21st century. This paper summarized the research status and progress of geopolymer in the aspect of soft soil solidification. The current geopolymer precursor and activator for soft soil solidification were introduced. The principle and mechanism of solidifying soft clay by geopolymer were summarized. The deformation and strength characteristics of geopolymer solidified soils were analyzed according to the laboratory element test results. The permeability and durability performance of the geopolymer solidified soils were discussed. The environmental impact and engineering applications of solidifying soft clay by geopolymer were summarized. Compared with the cement solidified soil, the geopolymer solidified soil had better mechanical properties with the same admixture, and it had lower CO₂ emissions. Therefore, the polymer can be used to replace cement for solidifying soft soil. In the future, geopolymer precursors with better performance and green activators should be further developed, and the macro- and micro-mechanical properties of different types of geopolymer solidified soils should be further investigated.

Review on Factors Affecting Setting and Hardening Characteristics of Geopolymers

LI Chao, LI Zhikang, LI Xinyu, HUANG Yongliang, WANG Wu, LUO Zhengdong, LI Wenjia, XU Fu

2025, 44(2):  501-514.  doi:10.16552/j.cnki.issn1001-1625.20241118.003

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Geopolymers are a family of inorganic cementitious materials formed by chemical excitation reaction of active aluminosilicate precursors, which have the advantages of excellent mechanical properties, good durability and so on. The development and application of this kind of new cementitious materials is conducive to the low-carbonation development of traditional cement industry. However, in the process of preparation of geopolymers, it is difficult to control the setting time of freshly mixed concrete, which greatly limits the adoption and application. This paper summarizes various factors that affect the setting and hardening behavior of geopolymers, such as the physical and chemical properties of aluminosilicate raw materials, the types, concentration and modulus of activators, water content and other internal factors, as well as the external factors such as curing temperature and chemical additives. The influence law and mechanism of each factor on the setting and hardening characteristics of geopolymers are discussed in detail, and the future research perspectives towards setting and hardening of geopolymers are also given on the basis of this comprehensive review.

Research Progress on Factors Influencing Heavy Metal Solidification Effect and Product Performance of Solid Waste-Based Ceramsite

CHEN Qinyuan, YAN Yifan, ZHAO Zhenhua, ZHANG Aiguo, GUAN Qiang, HE Yue

2025, 44(2):  515-530.  doi:10.16552/j.cnki.issn1001-1625.2024.1102

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As an important approach of resource utilization of industrial solid waste, sintered ceramsite not only has significant advantages in the heavy metal solidification, but also reduces the consumption of non-renewable resources such as clay and shale, making it a highly promising method for the resource utilization and harmless utilization of solid waste. In this paper, the solidification mechanism of heavy metals, the solidification effect (the solidification efficiency usually exceeds 80%), the application of ceramsite and the factors affecting the solidification effect of heavy metals and the product performance of ceramsite (bulk density, mechanical strength and water absorption) are systematically reviewed. Moreover, the current problems in the research of solid waste-based ceramsites and the possible research trends in the future are proposed, aiming to provide a scientific foundation for further improving the solidification efficiency of heavy metals and the ceramsite product performance of ceramsite sintered at high temperature.

Effect of Fly Ash Content on Workability of Fully Recycled Coarse Aggregate Self-Compacting Concrete

CHEN Xianghua, LAO Guowei, ZHENG Shufang, NING Fan, XU Ruitian, CHEN Zongping

2025, 44(2):  531-539.  doi:10.16552/j.cnki.issn1001-1625.20241118.001

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In order to prepare fully recycled coarse aggregate self-compacting concrete that meets the requirements of workability, 11 groups of fully recycled coarse aggregate self-compacting concrete mixtures were prepared with fly ash content (20%, 30%, 40%, 50%, 70%, mass fraction) and water-binder ratio (0.36, 0.40, 0.45) as design variables. The workability tests such as slump expansion, flow time T₅₀₀ and J-ring expansion were carried out, and the effects of fly ash content and water-binder ratio on the workability of fully recycled coarse aggregate self-compacting concrete were analyzed. The results show that the fluidity of fully recycled coarse aggregate self-compacting concrete can be improved by adding appropriate amount of fly ash. When the content of fly ash reaches 30% (mass fraction), the slump expansion of concrete reaches 755.0 mm. When the content of fly ash increases from 20% to 40%, the filling performance of concrete decreases, and the segregation rate decreases first and then increases. It is suggested that the reasonable content of fly ash in fully recycled coarse aggregate self-compacting concrete is 20%~30%. Based on the experimental results, a nonlinear regression model for the slump expansion of fully recycled coarse aggregate self-compacting concrete is established, and the calculated values are in good agreement with the experimental values.

Feasibility Study and Environmental Cost-Benefit Analysis of Molybdenum Tailings Sand Self-Compacting Concrete

YANG Puxin, FAN Minghui, LI Wei, REN Wenyuan, ZHANG Aijun

2025, 44(2):  540-549.  doi:10.16552/j.cnki.issn1001-1625.20241118.007

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In order to enhance the resource utilization of molybdenum tailings sand (MTs) and reduce the production cost of self-compacting concrete (SCC), the effect of MTs replacement rate on the working performance and mechanical performance of SCC under different sand rate was studied, and the resulting environmental and economic benefits were analyzed. The results show that the working performance of SCC decreases with the increase of MTs replacement rate, but SCC with good filling, gap passage and anti-segregation properties could be prepared by modulating the slump extension degree by changing sand rate and water reducer dosage. At 46% and 50% (mass fraction) sand rate, when the MTs replacement rate are 30% and 20% (mass fraction), the negative pore (less harmful holes, harmful holes and more harmful holes) percentage of SCC reduces and the compressive and splitting tensile strength significantly enhance. In addition, the incorporation of MTs effectively enhances the environmental and cost benefits. Considering the effects of MTs on the working performance, compressive strength, environment benefits and economic benefits of SCC, the study concludes that it is optimal to use 46% sand rate and 30% MTs replacement rate to prepare SCC in the neighboring areas where molybdenum tailings are abundant.

Mechanical Properties and Impact Resistance of Rubber Glass Powder Recycled Concrete

ZHAO Yi, LI Yu, HOU Dongchang, JIANG Mingxu, FENG Aozhong, SUN Yuzhou, MIN Zhiyu

2025, 44(2):  550-560.  doi:10.16552/j.cnki.issn1001-1625.20241118.006

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In order to improve the comprehensive utilization rate of solid waste in concrete, a new type of concrete with high efficiency of solid waste absorption was prepared. Through the optimization of raw materials and L₁₆ (4³) orthogonal test design, the effects of rubber particles (RP) replacing sand, glass powder (GP) replacing cement and recycled coarse aggregate (RCA) replacing natural coarse aggregate (NCA) on the mechanical properties and impact resistance of concrete were studied by range analysis and variance analysis. The Weibull distribution model was used to fit the impact test results and predict the failure probability. The results show that the primary and secondary order of the effects of various factors on the mechanical properties of concrete is RP, RCA and GP, and the primary and secondary order of the effects of various factors on the impact resistance of concrete is RP, GP and RCA. When RP content is 20% (volume fraction), compared with the RP content of 0%, the impact resistance increases by 81.8%, and the compressive strength and splitting tensile strength reduce by 21.63% and 12.65%, respectively. When GP content is 10% (mass fraction), compared with the GP content of 0%, the compressive strength, splitting tensile strength and impact resistance increase by 2.87%, 2.35% and 15.0%, respectively. When RCA content is 70% (volume fraction), compared with the RCA content of 0%, the compressive strength, splitting tensile strength and impact resistance reduce by 11.01%, 10.77% and 10.5%, respectively. Weibull distribution model can accurately describe the probability distribution of impact resistance times of rubber glass powder recycled concrete samples.

Effect of High Temperature on Properties of Fly Ash-Slag Based Porous Geopolymer

YANG Xuqing, WANG Hui, GAO Shang, GUO Meili, MENG Zehao, WU Yueyu

2025, 44(2):  561-568.  doi:10.16552/j.cnki.issn1001-1625.2024.0927

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Understanding the performance changes of porous geopolymers under high temperature conditions is helpful to optimize application porous geopolymer in high temperature environments. In this study, fly ash-slag based porous geopolymer materials were subjected to high temperature treatment at 200~800 ℃, and the effects of high temperature on the composition, microstructure and macroscopic properties of porous geopolymers were studied. The results show that the most significant mass loss of fly ash-slag based porous geopolymer occurs below 600 ℃, which is mainly attributed to the evaporation and dehydroxylation of free water and bound water. Above 600 ℃, the mass loss is weakened, mainly corresponding to the decomposition of some carbonate substances. The microstructure of porous geopolymer remains basically stable below 200 ℃, and hot cracking and melting begin to occur above 400 ℃. With the increase of heating temperature, the porosity, pore connectivity and average pore size of porous geopolymer increase continuously, the compressive strength decreases continuously, and the thermal conductivity decreases first and then increases.

Ratio Optimization and Characterization of Multi-Solid Waste-Based Geopolymer by Response Surface Method

HUANG Ziyu, DING Zhiyao, CAO Dan, SHEN Ding, YAO Shunyu, CHEN Yiren, REN Yanzeng, BAO Shenxu

2025, 44(2):  569-578.  doi:10.16552/j.cnki.issn1001-1625.2024.0937

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In this paper, coal slag, granite powder and high calcium fly ash were used as the main raw materials, and NaOH was used as the activator to prepare geopolymer. On the basis of single factor experiment, the Box-Behnken Design model in response surface method was used to analyze the effects of different solid waste mass blending ratios on the compressive strength of geopolymer. The phase composition and microstructure of the geopolymer were analyzed by XRD, FTIR and SEM. The results show that the order of the influence of the mass ratio of each solid waste on the response value is high calcium fly ash, coal-fired slag, granite powder. The interaction between granite powder and high calcium fly ash is significant. The optimal raw material ratio parameters obtained by response surface optimization are as follows: the mass ratio of coal slag is 1.8, the mass ratio of granite powder is 0.8, and the mass ratio of high calcium fly ash is 7.0. Under this ratio, the average compressive strength of geopolymer at early stage (7 d) can reach 22.73 MPa. Coal slag, granite powder and high calcium fly ash cooperate with each other to form amorphous gel phase and zeolite minerals through geopolymerization reaction, which provides strength for geopolymer. The grading effect of granite powder and high calcium fly ash makes the structure of geopolymer denser. This study can provide a reference for the synergistic disposal of bulk and multi-solid waste.

Preparation and Properties of Multi-Source Solid Waste-Based High Belite Ferroaluminate Cement

LI Xiangguo, GONG Zhixiong, MA Weinan, LI Shuguo, ZHANG Chengshan, DAN Jianming, LYU Yang

2025, 44(2):  579-589.  doi:10.16552/j.cnki.issn1001-1625.2024.0963

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This study utilized carbide slag, steel slag, desulfurization gypsum, and fly ash as primary raw materials, with bauxite as the corrective material, to synthesize high belite ferroaluminate cement (HBFAC). A comprehensive analysis including thermogravimetric analysis (TGA), burnability analysis, X-ray diffraction (XRD) analysis, heat of hydration analysis, scanning electron microscopy (SEM), and mechanical property tests was conducted to systematically investigate the sintering performance and hydration behavior of solid waste-based HBFAC clinker with varying belite content. The results show that the mineral formation temperature range of solid waste-based HBFAC clinker is between 1 220 ℃ and 1 340 ℃, with an optimal calcination temperature of 1 300 ℃, which is 25 ℃ to 100 ℃ lower than that of conventional sulfoaluminate cement (SAC) clinker. The optimal holding time is 30 min. Under optimal calcination conditions, solid waste-based HBFAC clinker exhibits well-developed and uniformly distributed crystals, with a setting time delayed by approximately 20~30 min compared to SAC. The solid waste-based HBFAC exhibits characteristics of rapid setting and hardening, early high strength, sustained strength growth at later stages, and low heat of hydration. Its compressive strength is superior to that of SAC and ordinary Portland cement (OPC). The main hydration products include ettringite (AFt), monosulfate (AFm), aluminum hydroxide gel (AH₃), and hydrated calcium aluminosilicate (C-A-S-H). Compared to tetracalcium aluminate sulfate (C₄A₃$\overline{\mathrm{S}}$), dicalcium silicate (C₂S) hydrates more slowly, contributing to the continued strength development of HBFAC in the later stage.

Solidification of Sand Washing Residue Mud byUsing Multivariant Solid Waste Cementitious Materials at 20 and 40 ℃

GAO Yunnan, ZHANG Lingshuai, HOU Li, ZHOU Yongxiang

2025, 44(2):  590-601.  doi:10.16552/j.cnki.issn1001-1625.2024.1094

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This study used granulated blast furnace slag, steel slag, red mud, calcined gypsum and a small amount of self-synthesized activator CH (made by mixing multiple valence states of alkali) and NS (made by mixing various soluble sulfates and halogen salts) to prepare multivariate solid waste cementitious materials (MSWCM) to solidify sand washing residue mud. The effects of chemical activator type, cementitious material content and curing temperature (20 and 40 ℃) on the compressive strength and microstructure of the solidified body of sand washing residue mud were studied by XRD, MIP and SEM. The water stability and heavy metal leaching characteristics were evaluated. The results show that the MSWCM with addition of CH has the best curing effect on the sand washing residue mud. When the curing temperature and the content of MSWCM are 40 ℃ and 40%, the 7 d compressive strength can reach 5.57 MPa, and the softening coefficient is 0.88. The solidification effect of sand washing residue mud is the worst for MSWCM with addition of NS, because of the lack of a high alkaline environment, which weakens the leaching of calcium and aluminum, reducing the generation of C-S-H and ettringite, and has a high porosity. The use of MSWCM with addition of CH-NS reduces the compressive strength of sample due to the formation of excessive expansion product AFt. By increasing the content of MSWCM and curing temperature, the compressive strength of solidified body of sand washing residue mud increases. The 7 d compressive strength of solidified body of sand washing residue mud at 40 ℃ can be increased by 169.08% compared with the 7 d compressive strength at 20 ℃ by MSWCM with addition of CH. In addition, the leaching content of heavy metals (iron, manganese, titanium) in the solidified body of sand washing residue mud meets the environmental protection requirements.

Engineering Property and Mechanism of Ground Granulated Blast Slag-Carbide Slag Composite Improved Expansive Soil

HU Qizhi, LI Junjie, TAO Gaoliang, LI Zitian

2025, 44(2):  602-612.  doi:10.16552/j.cnki.issn1001-1625.2024.0980

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Expansive soil is not suitable to be directly used for roadbed filling due to its characteristics of expansive softening by water absorption and shrinkage and cracking by water loss. The ground granulated blast slag (GGBS) and carbide slag (CS) were used to improve expansive soil. Through the compaction test, free expansion rate test, unconfined compressive strength test, and water stability test, the impacts of different ratios on the strength, water stability, and other engineering characteristics of improved expansive soil were studied. X-ray diffraction and scanning electron microscopy and other microscopic tests were carried out to study the composite improvement mechanism of GGBS and CS on expansive soil. The results show that the incorporation of GGBS and CS can inhibit the expansion characteristics of expansive soil and improve its strength and water stability. The composite improvement effect of 6%(mass fraction) GGBS and 6%(mass fraction) CS is the best, at this moment the free expansion rate is reduced to 11% after curing, the unconfined compressive strength is 2.84 MPa, and the water stability coefficient is 82.5%. Hydration reaction occurs between GGBS, CS, and expansive soil to form hydrated calcium silicate, hydrated calcium aluminate, and ettringite. Hydration products are cemented with each other, filling soil pores and bonding soil particles, making the soil denser, thereby improving the strength of improved expansive soil. The research results provide a reference for the application of GGBS and CS composite to improve expansive soil in roadbed engineering.

Interface Characteristics and Regulation of Core-Shell Structure Phosphogypsum-Based Aggregate/Portland Cement

HE Jing, LYU Wei, WU Chiqiu, YU Zhengkang, LI Yisheng, SHUI Zhonghe

2025, 44(2):  613-622.  doi:10.16552/j.cnki.issn1001-1625.2024.0977

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In order to solve the compatibility problem between phosphogypsum-based aggregate and ordinary Portland cement, a core-shell structure phosphogypsum-based aggregate was prepared in this paper. Based on the systematic study of the influence of the composition of aggregate shell on the macroscopic properties such as aggregate water absorption, cylinder compressive strength and compressive strength, the influence of the composition of aggregate shell on the microstructure characteristics of the interfacial transition zone of concrete was studied by means of modern analysis and testing methods. The results show that the performance of the core-shell structure phosphogypsum-based aggregate is improved compared with the uncoated aggregate, and the compressive strength of the concrete test block made of this aggregate and ordinary Portland cement is improved. The interface formed by phosphogypsum-based aggregate and cement with core-shell structure is compared with that without shell. In the early stage of hydration, the content of Ca(OH)₂ at the interface is reduced, the pore structure at the interface is optimized, the microhardness at the interface is improved, the width of the interfacial transition zone is reduced, and the shell layer can reduce the probability of S element in the aggregate core diffusing to the interface. In the later stage of hydration, the hydration reaction at the interface is basically stable, and the shell layer can still slow down the trend of S element diffusion from the core to the interface, reduce the risk of expansion and cracking at the interface, and increase the feasibility of the application of phosphogypsum-based aggregate in ordinary Portland cement system.

Early Mechanical Properties of Concrete Mixed with Recycled Coarse Aggregate and Recycled Powder

BI Yu, QIN Yongjun, LUO Ling, YAO Ziqi, LIU Fengchao, YANG Yiheng

2025, 44(2):  623-633.  doi:10.16552/j.cnki.issn1001-1625.2024.1066

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To address the issue of the low utilization rate of construction waste, this paper investigated the compressive strength of concrete prepared using recycled coarse aggregate and recycled powder from different acquisition methods and substitution methods. It also established a predictive model for the time-varying early compressive strength of concrete when mixing recycled powder and recycled coarse aggregate concrete, and analyzed the carbon footprint of the prepared concrete. The study included comparisons between over-substitution and standard substitution, as well as between recycled powder obtained by grinding and obtained by screening. Combined with scanning electron microscopy and mercury intrusion method, the micro-test of concrete samples was carried out, and the reasons for the micro-level change of concrete strength were analyzed. The results indicate that the impact of recycled powder on the mechanical properties of concrete is more significant than that of recycled coarse aggregate. As the content of recycled powder increases from 0% to 30% (mass fraction), the development of early compressive strength of the concrete gradually slows down. The porosity of concrete increases rapidly and the percentage of more hazardous hole also increases. In addition, the predictive model for the time-varying early compressive strength of recycled concrete established with the replacement rate of recycled powder and recycled coarse aggregate is well fitted, which can be used as a reference in engineering practice.

Effect of Synergistic Internal Curing by Rice Husk Ash and SAP on Properties of Alkali-Activated Slag Cementitious Materials

LYU Yang, WU Yuanshuai, Ge Yunlu, CHEN Yang, XU Jinsheng, JIAN Shouwei, DAN Jianming, WEN Xiaodong, LI Xiangguo

2025, 44(2):  634-641.  doi:10.16552/j.cnki.issn1001-1625.20241118.004

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Large early autogenous shrinkage and high cracking risk are important problems that limit the popularization and application of alkali-activated slag (AAS) cementitious materials. The use of superabsorbent polymer (SAP) for internal curing is one of the effective methods to solve these problems, but this method will reduce the mechanical properties of AAS. In this study, porous active rice husk ash (RHA) and SAP were combined to form a composite internal curing component (SAP-RHA, SR). The effects of SR and SAP internal curing on the working performance, shrinkage characteristics, hydration products and mechanical properties of AAS were compared and analyzed. The results show that compared with SAP internal curing alone, SR internal curing not only further reduces the autogenous shrinkage of AAS, but also effectively improves its compressive strength, which solves the problem of mechanical properties reduction caused by SAP internal curing to a certain extent.

Accounting Methodology for Carbon Reduction Using Recycled Aggregate from Construction Waste Instead of Natural Aggregate

ZHU Lei, SUN Jinting, JIA Hongtao, HOU Lei, LI Shuo, GUO Xinchen

2025, 44(2):  642-650.  doi:10.16552/j.cnki.issn1001-1625.2024.1052

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The resource utilization of construction waste has significant carbon reduction and low-carbon demonstration effects. However, the development of related emission reduction projects lacks applicable methodologies. This study aims to develop a carbon reduction accounting methodology for the replacement of natural aggregate with recycled construction waste aggregate. After defining the scope of application as the project activities of construction waste resource utilization factories, the methodology development adopts obstacle analysis method to identify and demonstrate the baseline scenario, and uses the difference comparison method of baseline and project emissions and the carbon emission factor method to calculate the emission reduction. The monitoring method specifies the parameters and data required for the design and implementation phases, with a focus on monitoring the various energy consumption, waste treatment volume, and recycled aggregate output of the production line during the implementation phase. The study verified the effectiveness and feasibility of methodology using a real project in Jiangsu Province. The results of this study not only fills the gap in the methodology of voluntary greenhouse gas reduction in the field of construction waste resource utilization, but also enriches the market-oriented action plans for the resource recycling utilization of construction waste from the carbon reduction accounting perspective.

Ceramics

Research Progress on Sintering Densification Technology of h-BN Ceramics

CHEN Yujie, LI Junsheng, LI Chenxiao, CHEN Yurong, WAN Fan

2025, 44(2):  651-665.  doi:10.16552/j.cnki.issn1001-1625.2024.1042

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Hexagonal boron nitride (h-BN) ceramics, as a type of high-performance structural-functional integrated composite ceramics material, have broad application prospects in aerospace, aviation, microelectronics, metallurgy, and other fields. However, due to the special layered structure and interlayer covalent bonds of h-BN, there are challenges in achieving density during the sintering process. In order to promote the densification of h-BN ceramics sintering and enhance their various properties, researchers have proposed new strategies based on traditional sintering techniques such as pressureless sintering (PLS), hot pressing sintering (HPS), spark plasma sintering (SPS), and reactive sintering (RS). Additionally, they have developed various new sintering technologies, including cold sintering (CSP), oscillating pressure sintering (OPS), and cross-linking pressureless bonding. This review comprehensively summarizes the recent advances in h-BN ceramics densification technology from the perspectives of both traditional and new sintering techniques. By comparing various traditional and new sintering technologies and combining them with typical applications of h-BN ceramics, it elucidates the development directions and application prospects of existing sintering technologies, aiming to provide references for the development and application of sintering densification technology for h-BN ceramics.

Microstructure and Mechanical Properties of 3D Printed C_sf/SiC Green Body Based on Vat Photopolymerization

HU Chuanqi, WANG Gong, LI Shan, JIN Baojie, LIU Bingshan, HONG Yiqiang, DAI Zhen, WANG Tiyuan, WANG Shuang

2025, 44(2):  666-678.  doi:10.16552/j.cnki.issn1001-1625.2024.0919

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Short cut carbon fiber reinforced silicon carbide composite (C_sf/SiC) is a kind of high-performance ceramic matrix composite. Vat photopolymerization 3D printing can make up for the shortcomings of traditional process in the precision manufacturing of complex fine structure C_sf/SiC components. In this paper, the photosensitive resin based C_sf/SiC slurry was prepared with short cut carbon fiber (C_sf), silicon carbide (SiC) micropowder and photosensitive resin. The test strips (A and B) with the movement direction of the scraper parallel to and perpendicular to the length direction of the test strip were obtained by the Vat photopolymerization 3D printing process. The changes of bending strength, Weibull modulus, size and weight of the two kinds of test strips before and after debonding were compared. The results show that the A test strip has higher strength and structural uniformity, and its density, bending strength and Weibull modulus are 1.81 g/cm³, 10.68 MPa and 13.22, respectively. After debonding, the density, bending strength and Weibull modulus of the green body decrease to 1.40 g/cm³, 7.32 MPa and 9.45, respectively. The debonding shrinkage in X, Y, Z direction are 1.22%, 3.35% and 4.24%, respectively. The brittleness of the green body increases and the toughness decreases. The chemical vapor infiltration (CVI) process can achieve the densification, toughening and homogenization of C_sf/SiC samples. The weight of debinded C_sf/SiC samples after CVI carburization increases about 50%, and the density, compactness, bending strength and Weibull modulus are 2.02 g/cm³, 93.88%, 121.22 MPa and 21.04, respectively.

Stereolithography Additive Manufacturing Process and Electrical Properties of Lead Zirconate Titanate Piezoelectric Ceramics

ZHU Kaifeng, HE Junchao, GONG Xiaolong, LIU Kai, SUN Huajun, SHI Yusheng

2025, 44(2):  679-689.  doi:10.16552/j.cnki.issn1001-1625.20240909.001

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Piezoelectric ceramics are important materials in electronic components, and their individualized and complex fabrication is important to improve the performance of piezoelectric functional devices. However, due to the high brittleness and hardness of ceramics, traditional molding processes face greater challenges in preparing complex structures. Additive manufacturing, based on the principle of layer-by-layer superposition, can theoretically prepare arbitrary complex structures, providing a new solution for the preparation of complex components of piezoelectric ceramics. In this paper, a lead zirconate titanate (PZT) piezoelectric ceramic skeleton with complex structure was successfully prepared using stereolithography (SLA) additive manufacturing process, and the effect of slurry solid content on the rheological properties of PZT ceramic slurry, the microscopic morphology, the relative density, and the electrical properties of PZT ceramic sintered body was investigated. The results show that the increase of ceramic solid content contributes to the grain growth at high temperature and the densification of billet, but at the same time increases the apparent viscosity of slurry and reduces the curing performance of slurry, which is not conducive to the preparation of PZT with complex structure. In this study, PZT-based ceramic sintered bodies with a relative density of 98.26% and a piezoelectric constant d₃₃ of 341 pC/N are prepared, which provides a reference for the additive manufacturing of high-performance piezoelectric ceramics and their composites.

Analysis on Applicability and Action Mechanism of Active Metal Method for Sealing Nonoxide Ceramics

YAO Zhongying, CUI Ge, REN Ruikang, REN Jiale, CHANG Yiwen, ZHANG Hongbo, KUANG Fenghua

2025, 44(2):  690-699.  doi:10.16552/j.cnki.issn1001-1625.2024.1089

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This article used the active metal method to seal nonoxide ceramics-nonoxide ceramics of the same composition (Si₃N₄-Si₃N₄, AlN-AlN, SiC-SiC) and nonoxide ceramics-metal material of different composition (Si₃N₄-4J29, Si₃N₄-304 stainless steel, Si₃N₄-oxygen free copper, SiC-4J29, SiC-304 stainless steel, SiC-oxygen free copper, AlN-4J29, AlN-304 stainless steel, AlN-oxygen free copper) in a vacuum welding furnace. The sealing strength of the samples was tested, and the morphology and elemental composition of the sealing interface were tested using SEM and EDS. The results show that the active metal method can be applied to the sealing of Si₃N₄- Si₃N₄, AlN-AlN, SiC-SiC, Si₃N₄-4J29, Si₃N₄-304 stainless steel, Si₃N₄-oxygen free copper, AlN-304 stainless steel, SiC-304 stainless steel, and SiC-oxygen free copper. Among them, the SiC-SiC sealing strength is the highest in the nonoxide ceramics-nonoxide ceramics sealing sample, reaching 129.4 MPa. The sealing strength of Si₃N₄-304 stainless steel (101.9 MPa), SiC-304 stainless steel (135.7 MPa), and AlN-304 stainless steel (79.1 MPa) in the nonoxide ceramics-metal material sealing samples are the higher. The core mechanism of the active metal method is that Ti in the solder migrates at the sealing temperature, with a portion diffusing from the center of the solder to the ceramics interface and forming TiN, TiC and other compounds with elements such as N and C, thus forming a relatively dense interface layer. There is also a small amount diffusing from the center of the solder to the metal, undergoing a solid fusion reaction with the metal, forming intermetallic compounds, and achieving high-strength sealing between heterogeneous materials.

Enhancing Properties of Ceramic Proppant for Coalbed Gas Exploitation by Stale Treatment

XING Li, GUO Linxiu, ZHANG Yunling, BAI Pinbo, GUO Lu, TIAN Yuming

2025, 44(2):  700-706.  doi:10.16552/j.cnki.issn1001-1625.2024.1030

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During the course of deep coalbed gas exploitation, the ceramic proppant with a good mechanical structure and flow conductivity are benefited to improve the mining efficiency of coalbed gas. Reprocessing of proppant raw materials is conducive to obtaining superior properties to meet the application in complex stratigraphy environment. In this paper, ceramic proppant for coalbed gas exploitation was prepared by using stale treatment on the low-grade bauxite and solid waste of coal gangue. The effect between the water wettability and sintering property was analyzed with the different stale interval. The variation rules of stale hydration were investigated on proppant about the microstructure density, pore distribution and phase size. Finally, the high-quality ceramic proppant was synthesized for satisfying the demand of coalbed gas mining, which provides the research basis for the efficient utilization of mineral resources and the stable exploitation of coalbed gas in the future.

Glass

Application and Performance Requirements of Glass Substrates in Chip Packaging

ZHANG Xingzhi, TIAN Yingliang, ZHAO Zhiyong, ZHANG Xun, WANG Ruzhi

2025, 44(2):  707-716.  doi:10.16552/j.cnki.issn1001-1625.2024.0916

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Glass substrates are set to become a critical material in advanced packaging technologies due to their superior high-frequency electrical properties, thermal stability, and chemical durability.This paper examines the roles and advantages of glass substrates in the packaging process, highlighting their applications in intermediary layers, fan-out packaging, micro-electro-mechanical system packaging, and integrated antenna packaging. This paper also summarizes the common composition and key physicochemical properties of glass substrates used in chip packaging, and provides insights into their future development.

Effect of Arsenic-Containing Soda-Lime Glass on Structure and Clarification Properties of High-Alumina Silicate Glass

HAN Huimin, SHI Wangming, DING Mengzhao, SHI Shiyan, SU Qi, LUO Lida

2025, 44(2):  717-725.  doi:10.16552/j.cnki.issn1001-1625.2024.0998

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High-alumina silicate glasses are of interest because of excellent mechanical, optical, and chemical tempering properties, but high melting temperatures can lead to difficulties in removing bubbles and streaks within the glass, which limits the preparation of high-quality glasses. As₂O₃ is a low-cost and efficient glass clarifier, but As₂O₃ has been banned due to safety factors. In this paper, sodium calcium glass prepared in a previous study that had solidified 12% (mass fraction) As₂O₃ was selected as a clarifier, and the effect of the introduction of arsenic-containing soda-lime glass on the network structure of high-alumina silicate glass was analyzed by FTIR spectra and Raman spectra. In addition, the effects of different As₂O₃ introduction amounts (0% to 0.5%, mass fraction) on the clarification effect of high-alumina silicate glass were investigated by using super depth-of-field microscopy. The results show that the polymerization of the network structure of high-alumina silicate glass decreases with the increase of the addition of arsenic-containing soda-lime glass. In addition, with the increase of As₂O₃ introduction amount, the bubble defects in high-alumina silicate glass are significantly reduced. When As₂O₃ introduction amount is 0.5%, the clarification effect is the best, and the bubble fusion ratio is as low as 0.14%.

Effect of ZrW₂O₈ on Structure and Properties of Phosphate Inorganic Adhesives

ZHANG Renxin, ZHANG Kuibao, JING Wei, QIN Xilong, LI Jie, WANG Yaozhi

2025, 44(2):  726-731.  doi:10.16552/j.cnki.issn1001-1625.2024.0863

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In recent years, high-precision and high-strength connections of complex parts have received widespread attention. This study employed amorphous phosphate adhesive as the base, incorporating fillers and curing agents including Si, B₄C, and ZrW₂O₈, to prepare a series of phosphate inorganic adhesives with varied coefficients of thermal expansion by adjusting the proportion. These adhesives were utilized for bonding β-lithium nesosilicate microcrystalline glass, effectively controlling its coefficient of thermal expansion. The bonded joints were thoroughly tested and characterized using techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, simultaneous thermal analyzer, scanning electron microscopy, bonding strength testing, and coefficient of thermal expansion testing. The findings indicat that the phosphate adhesive modified with ZrW₂O₈ demonstrates outstanding performance in bonding β-lithium nesosilicate microcrystalline glass, with heat-treated bonded joints exhibiting a coefficient of thermal expansion of 0.12×10^-6 K^-1 over the temperature range of 20~100 ℃, and a maximum bonding strength of 6.5 MPa.

Functional Materials

Research Progress on Al₂O₃-SiO₂ Aerogels and Their Fiber-Reinforced Composites

SUN Chuanqing, WANG Yang, LI Zhanfeng, MA Kui, WANG Mengmeng, LIU Ruixiang, LIU Futian

2025, 44(2):  732-745.  doi:10.16552/j.cnki.issn1001-1625.2024.0930

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The Al₂O₃-SiO₂ aerogel (ASA), due to its high porosity, low density and high specific surface area, exhibits outstanding high-temperature resistance and thermal insulation properties, holding broad development prospects in the field of aerospace thermal insulation. However, the relatively poor mechanical properties of ASA, weak infrared radiation absorption and heat dissipation capabilities at high temperatures limit its application in the field of high-temperature insulation. Element doping and fiber reinforcement are commonly used to improve the thermal insulation and mechanical properties of ASA. This paper provides an overview of ASA preparation techniques, factors affecting ASA properties, research on element or substance doped ASA, and fiber-reinforced ASA composites, while also offering insights into the future development directions of ASA.

Effect of Cr Content on Phase Evolution, High-Temperature Oxidation Resistance and Corrosion Resistance of FeNiCuCoCr_x (x=0, 0.5, 1.0, 1.5, 2.0) High-Entropy Alloys

CHEN Hao, WU Guangxin, QIAO Yunze, HUA Yu, LIU Changchun, YUAN Zixuan, HUANG Yingde, YANG Wenjie

2025, 44(2):  746-755.  doi:10.16552/j.cnki.issn1001-1625.2024.0985

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In this paper, the effect of Cr element on the phase composition, microstructure, phase evolution of FeNiCuCoCr_x(x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloy powders and on the high-temperature oxidation resistance and corrosion resistance of bulk high-entropy alloys were systematically investigated. The results show that the high-entropy alloy powders after mechanical alloying are composed of face-centered cubic (FCC) phase and body-centered cubic (BCC) phase. With the increase of Cr content, the strength of the characteristic peak of BCC phase increases. The BCC phase of FeNiCuCoCr_x(x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloys is dissolved in the matrix during high-temperature sintering, and the FCC phase is decomposed into Cu-rich phase (FCC1 phase) and Cu-deficient phase (FCC2 phase), and the microstructure and composition uniformity of the alloy is high. During the isothermal oxidation process at 900 ℃, the FeNiCuCoCr_0.5 high-entropy alloy forms a continuous and dense oxide film that adheres tightly to the substrate. When the thickness of the film is 25 μm, its high-temperature oxidation resistance is the best. The electrochemical tests results in 3.5% (mass fraction) NaCl solution reveal that the FeNiCuCoCr_0.5 high-entropy alloy exhibits the best corrosion resistance, with a corrosion current density of 5.56×10^-8 A/cm² and a charge transfer resistance of 6 821 Ω·cm². Compared to other FeNiCuCoCr_x(x=0, 1.0, 1.5, 2.0) high-entropy alloys, the corrosion current density is one order of magnitude lower. Compared to other FeNiCuCoCr_x(x=0, 1.0, 1.5, 2.0) high entropy alloys, the transfer resistance of FeNiCuCoCr_0.5 high entropy alloy increases by 51.9%, 18.8%, 233.4% and 265.3%. The research results provide new ideas for the composition design of corrosion-resistant FeNiCuCoCr high-entropy alloys.

Road Materials

Application of Orthoconcrete in Pavement Engineering

HUANG Zhijun, YU Zhen, SUN Zhijun, TAN Zonglin, LONG Chenjie, XU Wei, SHEN Weiguo, WANG Guiming

2025, 44(2):  756-764.  doi:10.16552/j.cnki.issn1001-1625.2024.0981

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In order to change the problems of a large amount of surplus concrete slurry and uneven distribution of aggregate settlement in pavement engineering, the C25 fluid concrete was transformed into orthoconcrete by using the distributing-filling aggregate process. The influence of coarse aggregate distributing-filling ratio on the mechanical properties, drying shrinkage and impermeability of orthoconcrete was studied, and the optimum distributing-filling ratio of coarse aggregate was changed by adjusting the dosage of water reducing agent. The interfacial transition zone and pore structure of orthoconcrete were analyzed. The results show that the aggregate distribution in orthoconcrete can be optimized by the distributing-filling aggregate process. Increasing the distributing-filling ratio can make the distribution of coarse aggregate in orthoconcrete uniform, improve the microstructure of interfacial transition zone, reduce the average pore size and porosity. The optimum distributing-filling ratio of coarse aggregate can be increased by 5 percent point when the original dosage of water reducing agent is increased by 10 percent point. In the range of 0%~25% coarse aggregate distributing-filling ratio, the strength of orthoconcrete increases first and then decreases with the increase of distributing-filling ratio.

Mechanical Properties and Durability of Red Sandstone Soil Solidified by Cement and Biological Enzyme

GUAN Hongxin, ZHANG Haixiang, YANG Hairong, YANG Fei, ZHENG Tianyi

2025, 44(2):  765-773.  doi:10.16552/j.cnki.issn1001-1625.2024.0566

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In order to study the performance of red sandstone soil solidified by biological enzyme soil curing agent and cement, and to explore the feasibility of composite solidified red sandstone soil used in expressway subbase, the effects of biological enzyme soil curing agent dosages on mechanical properties and durability of solidified soil were carried out, and microscopic tests were carried out in combination with scanning electron microscopy to analyze the stability mechanism. The results show that the addition of biological enzyme soil curing agent improves the unconfined compressive strength, splitting tensile strength, penetration resistance strength and elastic modulus of solidified soil, and the optimal dosage is 2‱. Under the same stress ratio, the fatigue life of composite solidified soil has no obvious advantage compared with that of single solidified soil by cement, but under the same stress, the fatigue life of composite solidified soil increases significantly compared with that of single solidified soil by cement. This study provides a reference for the practical engineering application of composite solidified red sandstone soil in expressway subbase.

Effect of Environmental Temperature on Mechanical Properties of Silicate Modified Polyurethane Grouting Materials

GUO Xiaoxiong, HUANG Qinhao, PENG Yang, YUAN Chao, LI Shuchen

2025, 44(2):  774-784.  doi:10.16552/j.cnki.issn1001-1625.2024.0936

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To analyze the applicability of organic-inorganic composite grouting materials in high temperature environments, this paper prepared a two-component silicate modified polyurethane grouting material with water glass, glycerol, and catalyst as component A, and isocyanate, plasticizer, and flame retardant as component B. The effect of environmental temperature on the mechanical properties of the new grouting material was discussed, and the environmental temperature response law of the strength of silicate modified polyurethane slurry was studied. The quartz-sandstone was used as the grouting matrix material to perform cracks, new materials were reinforced by grouting, and the bonding characteristics of the slurry rock interface were analyzed through microscopic experiments. The results show that under the effect of high temperature environment, the strength and elastic modulus of silicate modified polyurethane slurry consolidated body show a decreasing trend. At 25 ℃, the compressive strength, tensile strength, compressive elastic modulus, and tensile elastic modulus of the slurry consolidated body reach 48.16, 15.47, 507.47, and 520.10 MPa, respectively. When the environmental temperature increases to 90 ℃, they decrease to 38.13, 9.63, 387.57, and 410.84 MPa, respectively. The material has low sensitivity to environmental temperature. The increase in environmental temperature disrupts the equilibrium of chemical reactions between the two components, reduces the degree of organic crosslinking solidification and the compactness of the consolidated body, resulting in a decrease in strength of the materials.