Table of Content

Volume 44 Issue 9
15 September 2025

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Cement and Concrete

Influence of Iron Phase Modulation on Properties of High-Belite Ferroaluminate Cement

LI Xiangguo, SHI Xiangqin, AN Wandong, GONG Zhixiong, ZHANG Chengshan, LYU Yang

2025, 44(9):  3127-3136.  doi:10.16552/j.cnki.issn1001-1625.2025.0314

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With the increasing annual production of industrial solid waste in China and the implementation of the "dual-carbon" strategy, the development of high-performance cement that combines solid waste recycling with low-carbon characteristics has become a focus for industry transformation. This study utilized multi-source industrial solid wastes, including steel slag, carbide slag, fly ash, and desulfurization gypsum, to prepare high-belite ferroaluminate cement (HBFAC) through synergistic batching technology. The effects of iron phase content, calcination temperature, and holding time on the mineral composition, mechanical properties, and durability of HBFAC were systematically investigated. The results indicate that the optimal calcination parameters for HBFAC clinker are a temperature range of 1 275~1 325 ℃ and a holding time of 30 min. Under these conditions, the iron phase (15%~25%, mass fraction) stabilizes the crystal structure of ye'elimite (C₄A₃S) and promotes its growth. Compared to ordinary Portland cement and sulfoaluminate cement, HBFAC exhibits superior performance in both early-age strength development and long-term strength gain. HBFAC in 5% (mass fraction) Na₂SO₄ solution shows excellent sulfate resistance, the corrosion resistance coefficient all exceeding 1. When calcined at 1 275 ℃ with 25% iron phase content, HBFAC achieves a remarkable 90 d corrosion resistance coefficient of 1.522. The sulfate resistance mechanism is attributed to the synergistic effect of ettringite (AFt) and ferro-aluminum gel induced by the iron phase, which fills pores and forms a dense structure, effectively blocking SO₄^2- attack. This study provides a theoretical foundation for the application of industrial solid waste-based HBFAC in harsh environments (e.g., marine engineering, saline soils), achieving the dual objectives of solid waste utilization and high-performance material development.

Durability Study of Cement-Sodium Silicate Double Slurry Grout Consolidation Body under Accelerated Erosion by High Chloride Salts

WANG Qianqian, DAI Hang, WANG Lichuan, ZHANG Chunyu, LI Liping, WANG Haiyan, ZHANG Jingjing

2025, 44(9):  3137-3146.  doi:10.16552/j.cnki.issn1001-1625.2025.0184

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As a grouting material for water plugging and reinforcement, the service performance and degradation mechanism of cement-sodium silicate (C-S) double slurry grout under high chloride salt erosion have not been studied systematically. In this paper, the effects of water-cement ratio (w/c) and water glass concentration on the workability of C-S double slurry grout, the mechanical properties, phase evolution and pore structure of C-S double slurry grout consolidation body (referred to as C-S consolidation body) under high chloride salt curing environment were studied by macroscopic and microscopic tests such as compressive strength, X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results show that the chemical gelling time of C-S double slurry grout is shortened with the decrease of w/c and water glass concentration in a certain range, and the chemical gelling time is less than 35 s, which meets the demand of rapid water plugging. In the curing environment with chloride concentration greater than 15% (mass fraction), the compressive strength of C-S consolidation body with two optimal mix ratios (w/c of 0.6, water glass concentration of 34°Bé and w/c of 0.7, water glass concentration of 30°Bé) is higher than that of water curing environment before 56 d of curing. In addition, the C-S consolidation bodies of the two optimal mix ratios still show good resistance to chloride salt corrosion after 90 d of curing. Microscopic analysis shows that under high chloride salt concentration, the C-S consolidation body generates Friedel's salt (Fs) in the short-term, and the mechanical properties are improved. However, long-term erosion will lead to decalcification of hydrated calcium silicate (C-S-H) gel and decrease of mechanical properties.

Effect of Ambient Temperature on Hydration Temperature Rise of Magnesium Phosphate Cement

JIANG Haoyang, HU Zhide, ZHAO Sixie, ZHANG Hansong, XU Chunxia

2025, 44(9):  3147-3155.  doi:10.16552/j.cnki.issn1001-1625.2025.0057

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Ambient temperature is one of the important factors affecting the construction and application of magnesium phosphate cement (MPC). In this paper, the hydration temperature rise characteristics, compressive strength, hydration product composition, and pore changes of magnesium ammonium phosphate cement (MAPC) and magnesium potassium phosphate cement (MKPC) were systematically analyzed at different ambient temperatures. The results show that the increase in ambient temperature caused an increase in the hydration temperature peak of MAPC and MKPC. With the increase of the ambient temperature, the hydration temperature peak of MAPC appears earlier. In contrast the hydration temperature peak of MKPC first shifts forward and then backward in timing, with relatively lower peak values. As the hydration temperature peak increases, the compressive strength of MAPC and MKPC both show the same trend of first increasing and then decreasing, but there are significant differences in the hydration products and pore changes. MAPC produces different hydration products at different hydration temperature peaks. When the hydration temperature peak is below 70.0 ℃, the main product is MgNH₄PO₄·6H₂O, and its production increases with the increase of hydration temperature peak. When the hydration temperature peak is above 70.0 ℃, a poorly adhesive hydration product MgNH₄PO₄·H₂O is generated, which causes an increase in harmful pores. The hydration products of MKPC are all MgKPO₄·6H₂O, and the generated amount increases with the increase of the hydration temperature peak. However, at high hydration temperature peaks (above 60.0 ℃), rapid water evaporation causes an increase in the proportion of harmful pores.

Influence of Epoxy Rein Components on Performance of Epoxy Resin Mortar

ZHANG Shufeng, WANG Lei, XU Shilong, CAI Jiacheng, CHEN Jinfan, HUANG Jizhi

2025, 44(9):  3156-3167.  doi:10.16552/j.cnki.issn1001-1625.2025.0251

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In this work, orthogonal experimental approach was employed to investigate the effects of two bisphenol-A type epoxy resins (single and compound blending), two reactive diluents (single and compound blending), and five curing agents on the mechanical and bond properties of epoxy resin mortar. Results show that the effects of three factors on the flexural strength and compressive strength of epoxy resin mortar from large to small is curing agent, epoxy resin and diluent, and the influence of curing agent type is much greater than other two factors. All three factors exhibit comparable influence on the dry and wet bond strength of epoxy resin mortar. SEM and XRD analyses reveal the absence of Ca(OH)₂ crystals in the epoxy resin mortar, indicating that the epoxy resin mortar system effectively inhibit cement hydration and growing stresses from Ca(OH)₂ crystallization, thus enhancing both compressive strength and flexural strength of epoxy resin mortar.

Effect of Grain Shape of Glutenite Manufactured Sand on Concrete Properties

ZHU Zilong, CHEN Peichong, LIAO Jie, YANG Xuan, ZHAO Deqiang, QU Liangchen, WANG Guiming, SHEN Weiguo

2025, 44(9):  3168-3177.  doi:10.16552/j.cnki.issn1001-1625.2025.0244

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Promoting the utilization of glutenite manufactured sand in concrete is of significant importance. In this study, river sand and granite manufactured sand were used as references. Digital image processing (DIP), laser scanning microscopy (LSM), and the aggregate image testing system (AIMS) were employed to systematically characterize the grain shape of the glutenite manufactured sand. The influence of grain shape parameters on the workability and mechanical properties of C30 concrete was investigated. Furthermore, scanning electron microscopy and mercury intrusion method were used to elucidate the mechanisms of grain shape of manufactured sand on hydration products and pore structure of concrete. The results show that the river sand concrete with the smallest roundness exhibit the best workability, while the granite manufactured sand concrete with the largest roughness and angularity exhibits the optimal mechanical properties. The roundness, angularity and roughness of the glutenite manufactured sand are between river sand and granite manufactured sand. Glutenite manufactured sand concrete exhibits lower porosity and achieves 28 d compressive strength of 43.5 MPa, flexural strength of 5.7 MPa, and splitting tensile strength of 3.66 MPa. The glutenite manufactured sand can not only meet the performance requirements of C30 concrete, but also provide a feasible new scheme for the resource utilization of waste rock produced in the process of highway excavation.

Workability Prediction of Self-Compacting Concrete Based on CatBoost Optimization Algorithm

LIANG Qimin, WANG Zhe, MEI Yingjie, SUN Ao, LI Pengfei

2025, 44(9):  3178-3187.  doi:10.16552/j.cnki.issn1001-1625.2025.0079

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Aiming at the problem that improper control of self-compacting concrete workability can easily lead to defects in concrete structure, this paper presents a method of predicting self-compacting concrete workability based on CatBoost optimization algorithm. First of all, a dataset consisting of 313 sets of data was established through experiment. Subsequently, a predictive model for self-compacting concrete workability was established based on the CatBoost algorithm, and the optimal model hyperparameters were determined using the Optuna automatic hyperparameter optimization framework. Finally, the input parameters of the model were analyzed. The results show that, compared with the dataset without the inclusion of paste test data, the dataset established in this study can effectively improve the prediction accuracy of self-compacting concrete workability. The paste test data exhibits strong correlation and importance in the prediction process. The developed model can accurately predict slump flow and V-shaped funnel time, indicating that the model has good generalization ability and can provide a reference for the design and application of self-compacting concrete.

Evaluation of Rheological Properties of High-Strength Self-Compacting Concrete Cement Paste Based on Water Film Thickness

HU Yanyan, XIE Bingqian, ZHAO Bing

2025, 44(9):  3188-3195.  doi:10.16552/j.cnki.issn1001-1625.2025.0218

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To investigate the effect of ultrafine fly ash (UFA) on the rheological properties of cement paste in high-strength self-compacting concrete (HSSCC), this study tested the influences of different UFA dosages on the fluidity, rheological properties, packing density, and water film thickness (WFT) of C60 and C80 HSSCC cement pastes. The results show that when the UFA dosage is 15% (mass fraction), the fluidity of both cement pastes reaches their maximum, while the yield stress, apparent viscosity, and thixotropy reach their minimum. At this dosage, the packing density of both cement pastes is also at their highest. The packing density of C80 HSSCC cement paste is higher than that of C60 HSSCC cement paste, whereas the WFT of C80 HSSCC cement paste is lower than that of C60 HSSCC cement paste. Specifically, the WFT of C60 HSSCC cement paste is 0.195 7 μm, while that of C80 HSSCC cement paste is 0.037 1 μm. Polynomial regression fitting reveals a strong correlation between WFT and the yield stress of cement paste.

Fracture Mechanical Properties of Concrete Exposed on High Temperatures Based on DIC

WANG Lei, RAO Bin, ZHAO Yanru, XU Youjun, CHEN Ming

2025, 44(9):  3196-3206.  doi:10.16552/j.cnki.issn1001-1625.2025.0257

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Three-point bending fracture tests were conducted on notched concrete beams at different temperatures (20, 200, 400, 600 and 800 ℃), and the surface deformation field was observed using the digital image correlation(DIC) method. By defining a strain boundary threshold, the fracture process zone of concrete was identified. Based on fracture mechanics theory, the initial fracture toughness, unstable fracture toughness and fracture energy of concrete were calculated. The variation law of fracture properties with temperature was analyzed. The results indicate that as temperature increases, the fracture process zone appears earlier, and the stable crack propagation phase is extended. The growth rate of the fracture damage factor accelerates with rising temperature during the early loading stages and gradually slows down near the peak load, suggesting that elevated temperatures cause the fracture process of concrete to transition from brittle to ductile. Both the initial and unstable fracture toughness decrease gradually with increasing temperature. The fracture energy gradually increases from 200 ℃ to 600 ℃ due to enhanced ductility and post-peak deformation capacity of concrete at high temperatures, but it significantly decreases at 800 ℃ as a result of material decomposition.

Early Shrinkage Cracking Performance of Aeolian Sand PVA-FRCC Plate in Windy and Hot-Dry Environment

WANG Yuqing, XUE Yanzhao, YUN Zeya, SUN Huajun, LIU Shuguang

2025, 44(9):  3207-3217.  doi:10.16552/j.cnki.issn1001-1625.2025.0173

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To explore the early-age (7 d) restrained shrinkage and cracking performance of polyvinyl alcohol fiber reinforced cementitious composite (PVA-FRCC) plate containing aeolian sand under windy and dry-hot environment in western China, and to promote the engineering application of aeolian sand, thereby reducing the exploitation of natural aggregates, this study was carried out. In this study, the early shrinkage performance of PVA-FRCC plate was studied by taking the aeolian sand replacement rate, fiber volume fraction, water-binder ratio and restrained degree as variables, and the shrinkage estimation model was established. The results show that the restrained shrinkage increases with the increase of aeolian sand replacement rate and water-binder ratio. The incorporation of PVA fiber can not only reduce the restrained shrinkage, but also significantly improve the crack resistance of aeolian sand PVA-FRCC plate. When the aeolian sand replacement rate is higher and the water-binder ratio is slightly larger, the crack resistance grade of aeolian sand PVA-FRCC plate is the highest. From the comprehensive performance of shrinkage performance, mechanical performance, aeolian sand utilization rate and economy, it is better to mix a certain amount of PVA fiber, moderate aeolian sand replacement rate and small water-binder ratio. The internal humidity change of aeolian sand PVA-FRCC plate is divided into three stages, which is highly correlated with the shrinkage change law, reflecting the shrinkage change mechanism. Through theoretical analysis, the early restrained shrinkage estimation model of aeolian sand PVA-FRCC plate is established. The calculated value of the model is in good agreement with the experimental value, which can provide reference for the early shrinkage estimation and crack control of aeolian sand PVA-FRCC plate.

Effect of Abrasion on Physical Properties and Apparent Morphology of Recycled Concrete Aggregates

LYU Jieqin, YUAN Hao, GAO Ling, WANG Yan, GU Yang, SUN Renjuan

2025, 44(9):  3218-3226.  doi:10.16552/j.cnki.issn1001-1625.2025.0222

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To investigate the effects of physical abrasion on the physical properties and morphological characteristics of recycled aggregates derived from parent concrete of varying strengths, recycled coarse aggregates were produced from C35, C40, and C50 grade concretes and subjected to physical enhancement using a Los Angeles abrasion machine. The influences of steel ball quantity and number of revolutions on the apparent density, water absorption, and crushing value of recycled aggregates from different parent concrete strengths were examined. The aggregate image measurement system (AIMS) was employed to collect morphological characteristics of the aggregates before and after abrasion treatment, focusing on angularity, texture, and sphericity. The results show that the physical properties and morphological characteristics of recycled aggregates are significantly influenced by the number of steel balls, rotation counts, and parent concrete strength. Under the condition of 8 steel balls and 400 revolutions, the apparent density of C35 recycled aggregates increases by 1.52%, the water absorption decreases by 36.05%, and the crushing value reduces by 27.41%. Additionally, the angularity index decreases by 34.28%, the sphericity increases by 19.61%, and the texture index increases by 9.30%. Further increasing the number of steel balls or revolutions leads to secondary crushing of the aggregates, resulting in diminished performance improvement. Apparent density is negatively correlated with parent concrete strength, while the crushing value shows a positive correlation. Water absorption does not exhibit a clear correlation, showing a fluctuating trend. Angularity index and sphericity show a decreasing-then-increasing trend with increasing strength, whereas texture index displays an opposite trend. The abrasion condition of 8 steel balls and 400 revolutions can simultaneously improve the physical properties and optimize the morphological characteristics of recycled aggregates, providing a theoretical basis for their refined processing.

Sodium Bicarbonate Solution Carbonation: a Novel Method to Enhance Recycled Aggregate Concrete Performance

YI Qigui, ZHAN Lyujin, LIU Xiang, XU Ruitian, LIANG Ying, CHEN Zongping

2025, 44(9):  3227-3237.  doi:10.16552/j.cnki.issn1001-1625.2025.0367

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Sodium bicarbonate (NaHCO₃) solution can improve carbon fixation efficiency and early mechanical properties of recycled aggregate concrete (RAC), but the effect of NaHCO₃ solution concentration on the mechanical properties of RAC is not yet clear. This article focused on different concentrations of NaHCO₃ solution (0~10.0 g/L) and carbonation environments (natural environment, carbonation box, standard curing box, water environment, NaHCO₃ solution) as the main variables. Cube and prism compression tests and four point bending tests were conducted on 72 specimens, and the carbon sequestration was evaluated through thermogravimetric analysis. The results show that the presence of NaHCO₃ enhances the mechanical properties of RAC in water environment, especially at a solution concentration of 10.0 g/L. As the concentration of NaHCO₃ solution increases, the carbon sequestration of RAC gradually increases and is greater than that of RAC in the carbonation box environment. In addition, the strength indexes show a trend of first decreasing and then increasing, with the maximum increase in axial compressive strength and flexural strength of RAC reaching 12.1% and 31.9%, respectively. Finally, a new method for calculating the strength of NaHCO₃ solution carbonation RAC was proposed.

Effect of Seawater Fluidity on Chloride Ions Diffusion Performance in Concrete

YU Aiping, CHENG Zichen, LI Zhengkang, LI Xiuxin, LIU Yongqi, CHEN Xuandong

2025, 44(9):  3238-3245.  doi:10.16552/j.cnki.issn1001-1625.2025.0503

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To investigate the influence of seawater flow on chloride transport behavior in concrete, this study simulated real marine environments using artificial seawater with 5 times normal concentration. Three flow conditions were set: 0 (static), 0.21 and 0.42 m/s. A systematic study was conducted combining chloride ion concentration measurements with microstructural characterization techniques including XRD, SEM, and mercury intrusion porosimetry (MIP). The results demonstrated that, seawater flow significantly accelerated chloride ion adsorption in the concrete surface layer during the initial erosion stage (60 d), with chloride ion concentrations under 0.21 and 0.42 m/s conditions being notably higher than in static seawater. After long-term erosion (180 d), the difference in chloride ion concentration between flowing and static conditions gradually diminished, indicating that seawater flow has limited influence on chloride diffusion behavior within concrete. Microstructural analysis shows the formation of ettringite and Friedel salt during erosion, but no microcracks induced by ettringite crystallization are observed, suggesting sulfate ions play a minor role in concrete deterioration. Furthermore, MIP tests show similar pore size distributions across all three conditions, confirming that seawater flow has minimal impact on the internal reaction mechanisms of concrete. This study elucidates the transport characteristics and time-dependent patterns of chloride ions under flowing seawater conditions, providing a theoretical basis for durability design and service life prediction of marine concrete structures.

Conventional Triaxial Compressive Mechanical Properties of Foamed Lightweight Concrete

YANG Qingyuan, WANG Yao, SHAN Hongri, LI Hui, CHEN Cong, JIANG Nengdong

2025, 44(9):  3246-3254.  doi:10.16552/j.cnki.issn1001-1625.2025.0258

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This study investigated the stress-strain curves, failure modes, and shear strength characteristics of foamed lightweight concrete under different confining pressure levels through conventional triaxial compression tests. The results show that the triaxial compressive strength significantly increases with the increase of confining pressure level, but the growth rate slows down with the increase of confining pressure level. Within the confining pressure level range of 0.1 to 0.5, the conventional triaxial compressive strength increases by 1.5 times to 2.5 times relative to the uniaxial compressive strength. Lateral pressure has a significant impact on the failure mode of the specimens. Without confining pressure, a triangular constrained area is formed at the end of the specimen and diagonal cracks occur. With confining pressure, shear failure is the main manifestation. Under high confining pressure, the fracture area of the specimen is difficult to expand laterally, the main crack width is reduced, and the extrusion plastic flow occurs, resulting in large plastic deformation. Analysis using the Mohr-Coulomb criterion reveals that the cohesion and internal friction angle of foamed lightweight concrete are positively correlated with wet density, and the cohesion is approximately linearly related to porosity. These research findings provide a theoretical basis and technical support for the application of foamed lightweight concrete under complex stress states.

Solid Waste and Eco-Materials

Research Progress on Preparation, Characterization and Application of Modified Bentonite Materials

YI Shirong, ZHANG Miaomiao, CHEN Sisi, WANG Linlin, NI Yuhang, HAN Zhiwei, ZHAO Dan

2025, 44(9):  3255-3271.  doi:10.16552/j.cnki.issn1001-1625.2025.0122

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Bentonite is a natural non-metallic mineral resource. Transforming it into valuable products through advanced technological means and applying them in various fields of social production such as industry, agriculture and environmental governance is an important way to achieve resource recycling and reduce negative environmental impacts. This paper reviews the current preparation methods, characterization techniques and application status of modified bentonite materials at home and abroad, summarizes the methods and principles for improving the performance of bentonite and the characterization and testing methods, analyzes the application potential and shortcomings of modified bentonite in soil improvement, remediation agents, fertilizer additives, pesticide adsorbents and fields such as electronics, automobiles and aerospace, and looks forward to the future development direction of modified bentonite materials, providing useful references and inspirations for the research and development of high-performance modified bentonite materials.

Properties and Microstructure of Cement Solidified Incineration Fly Ash-Cement Composites Cementitious Material

LIU Jiayu, GAO Yu, LIU Ze, WEN Shuaiyun, WANG Dongmin, WEI Peng, ZHANG Chunhui, ZHU Zhengjiang, LI Qingya

2025, 44(9):  3272-3279.  doi:10.16552/j.cnki.issn1001-1625.2025.0208

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Cement solidified incineration fly ash (CSFA) has a large landfill volume and causes pollution to the environment, but it has a high calcium content and potential volcanic ash activity, which can be used to prepare cementitious materials. In this paper, using detoxified cement solidified incineration fly ash (DCSFA) as raw materials, the physical and chemical characteristics, mechanical properties and microstructure of the hardened slurry of detoxified cement solidified incineration fly ash-cement composite cementitious materials (C-DCSFA) were studied. The results show that the mechanical properties of the C-DCSFA with a 10% (mass fraction, the same below) dosage of DCSFA are better than cement group at 7 and 28 d, and the highest compressive strength at 28 d can reach 53.4 MPa. The addition of 10% DCSFA results in lower early performance of the composite cementitious material compared to the cement group after 3 d, slower early hydration process, and lower cumulative heat release. As the reaction progresses, the composite cementitious material exhibits alternating growth of hydration products and tight connections at 28 d, resulting in a significant increase in its compressive strength.

Experimental Study on Solidification of Municipal Solid Waste Incineration Fly Ash Using High-Strength Sulfoaluminate Cement-Based Materials

DONG Faxin, XU Zifan, WANG Junfeng, LU Liulei, YE Weikai, SHANG Chunjing

2025, 44(9):  3280-3287.  doi:10.16552/j.cnki.issn1001-1625.2025.0210

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Municipal solid waste incineration fly ash (MSWI FA) is included in the national hazardous waste list because it is rich in harmful substances such as heavy metals and dioxins. Its safe disposal is an urgent need for environmental protection. Sulfoaluminate cement (SAC) has become an ideal cementitious material for solidifying MSWI FA due to its advantages of early strength, fast hardening, corrosion resistance and low carbon emission. High-strength mortar was prepared by adding 5%~20% (mass fraction, the same below) MSWI FA into SAC. The effect of MSWI FA content on mechanical properties, microstructure and environmental safety of solidified body was studied. The results show that when the content of MSWI FA is 5%, the 6 h compressive strength of mortar is 44.8 MPa, which is only 3.9% lower than that of blank group. The compressive strength at 28 d is 91.6 MPa, which is 16.2% lower than that of blank group, and the setting time is shortened by 34.9%. When the content of MSWI FA is 20%, the 28 d compressive strength of mortar is 60.2 MPa and the porosity is 18.0%. Microscopic analysis shows that chloride ions react with calcium sulfoaluminate to form hydrocalumite, which inhibits the formation of ettringite and leads to pore coarsening. In addition, the leaching concentration of heavy metals in each group of high-strength solidified body meets the limit value of “Pollution control standard for domestic waste landfill site” (GB 16889—2024), and the carbon emission is 44.7% lower than that of traditional Portland cement at 20% MSWI FA content, which provides a theoretical possibility for the recycling of hazardous waste and the development of low-carbon building materials.

Piezoresistive Performance of Alkali-Activated Superfine Powder-Fly Ash Cementitious Materials

KONG Weipeng, PANG Laixue, GUO Wei, TIAN Xiaofeng

2025, 44(9):  3288-3294.  doi:10.16552/j.cnki.issn1001-1625.2025.0294

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A novel alkali-activated cementitious material was successfully fabricated using fly ash and superfine powder as raw materials, while NaOH and Na₂SiO₃ were employed as alkali activators and its piezoresistive performance was tested. The results show that when the curing age reaches 28 d, the maximum resistivity change rate of alkali-activated cementitious material using NaOH as the alkali activator is 44.2%, whereas that for the material activated by Na₂SiO₃ is 54.2%. The main hydration products of alkali-activated cementitious material with Na₂SiO₃ as alkali activator is tobermorite and calcium silicate hydrate gel. The hydration products fill the internal voids, and the pore structure tends to be dense. The resistivity change rate is positively correlated with piezoresistive performance, the alkali-activated cementitious material of Na₂SiO₃ system has a greater resistivity change rate, therefore, its piezoresistive performance is better.

Properties of Composite Cementitious Materials under Low Temperature and Low Pressure Curing Conditions

ZHANG Xiaolong, WANG Wei, YAO Aijun, WANG Zhaohui, FENG Xihao, WANG Jie

2025, 44(9):  3295-3304.  doi:10.16552/j.cnki.issn1001-1625.2025.0280

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In this study, according to the environmental characteristics of the northwest alpine region, fly ash and slag powder were used as raw materials to partially replace cement to prepare composite cementitious materials. The development of mechanical properties and microstructure evolution law of composite cementitious materials were investigated by curing at low temperature (0, 8, 15 ℃) and low pressure (0.06 MPa) conditions and comparing with standard curing (20 ℃, 65 kPa) conditions. The results show that the mixed fly ash and slag powder can produce efficient synergistic effect, but with the decrease of temperature, this effect gradually weakens, and the compressive strength and flexural strength of sample also decrease. Under the same low temperature conditions, with the decrease of fly ash content and the increase of slag powder content, the flexural strength and 7 and 28 d compressive strength of composite cementitious materials gradually increase, while the 3 d compressive strength decreases first and then increases. When the content of fly ash and slag powder is 10% (mass fraction) and 50% (mass fraction) respectively, the flexural strength and compressive strength are the largest. The microscopic test results show that the low temperature and low pressure curing conditions limit the hydration reaction rate of cementitious materials, resulting in the gradual reduction of hydration products. With the decrease of fly ash content and the increase of slag powder content, the content of chemically bound water and calcium hydroxide gradually increases, indicating that the active components of slag powder can still promote the hydration reaction at low temperature, thereby enhancing the mechanical properties of cementitious materials.

Foaming Behavior and Crystalline Phase Transition of Red Mud-Based Ceramsite under Low Oxygen Partial Pressure

TANG Pei, GUO Shaofei, DENG Tengfei, CHEN Wei

2025, 44(9):  3305-3314.  doi:10.16552/j.cnki.issn1001-1625.2025.0268

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Red mud, an alkaline solid waste generated in the aluminum industry, holds significant potential for efficient resource utilization to alleviate environmental pressure and promote sustainable development. This study aimed to optimize the performance of red mud-based ceramsite by systematically investigating the influence of aluminum-to-silicon molar ratio (A/S) variations on the foaming behavior, physical properties, crystalline phase composition, and pore structure under a nitrogen atmosphere. Results demonstrate that low oxygen partial pressure promotes the decomposition of hematite in red mud, generating FeO that preferentially reacts with Al₂O₃ to form granular hercynite (FeAl₂O₄). As the A/S increases, the content of spinel and plagioclase phases in the ceramsite rises significantly. This evolution in crystalline phases profoundly influences the properties of high-temperature melts and pore structure, thereby enhancing matrix strength. Based on these findings, lightweight high-strength ceramsite with compressive strength of 3.48 MPa, water absorption of 0.31%, apparent density of 0.72 g/cm³, and porosity of 76.6% is successfully prepared under conditions of 20% (mass fraction) red mud and 1 170 ℃ holding for 60 min in nitrogen atmosphere. This study provides valuable insights into the efficient utilization of red mud and the development of high-performance ceramsite.

Influences of Different Foaming Agents on Microstructure and Properties of Lithium Slag Foam Glass

CHEN Kun, LIAO Qilong, LIU Laibao, WANG Fu, ZHU Hanzhen, SHI Xianpan, DAN Yong, ZHAO Peng

2025, 44(9):  3315-3325.  doi:10.16552/j.cnki.issn1001-1625.2025.0223

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With the rapid development of the lithium battery industry, the resource utilization of the massive amount of lithium slag has become an urgent issue to be solved. In this study, lithium slag was used as the main raw material to prepare foam glass, with MnO₂, SiC and CaCO₃ introduced as foaming agents. The effects of different types and content of foaming agents on the foaming process, pore structure and physical properties of the foam glass were systematically investigated, and the corresponding foaming mechanisms were elucidated. The results show that increase the content of MnO₂ and CaCO₃ leads to increase of pore size and decrease of bulk density, compressive strength and thermal conductivity. With the increase of SiC content, pore size decreases and bulk density, compressive strength and thermal conductivity increase. Excessive MnO₂ forms open-cell structures, whereas SiC and CaCO₃ forms closed-cell structures. When the MnO₂ content is 4%～5% (mass fracton) and SiC content is 1%～2% (mass fracton), the foam glass exhibits optimal comprehensive performance, with a bulk density of 0.35～0.44 g/cm³, compressive strength of 1.24～2.99 MPa, and thermal conductivity of 0.058～0.065 W/(m·K), meeting industry standard. This study provides theoretical support and a technical pathway for the high-value utilization of lithium slag.

Effect of Early CO₂ Curing on Properties of Steel Slag Solid Waste Cementitious Material

YE Jisheng, MA Ying, LI Yuwei, TAI An, WANG Jiahao

2025, 44(9):  3326-3336.  doi:10.16552/j.cnki.issn1001-1625.2025.0304

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In order to promote the low-carbon and resource utilization of steel slag, steel slag combined with ground blast furnace slag, desulfurized gypsum and a small amount of cement were used to prepare steel slag solid waste cementitious materials. The effect of early CO₂ curing on the properties of steel slag solid waste cementitious materials was studied by compressive strength, product composition, microstructure, volume stability and soundness analysis. The results show that the compressive strength and linear expansion rate of steel slag solid waste cementitious materials under early CO₂curing are lower than those non-carbonation curing. Under early CO₂ curing, when the steel slag content (40%~45%, mass fraction) is low and the ground blast furnace slag content (32%~35%, mass fraction) is high, the early compressive strength of steel slag solid waste cementitious material is high, up to 14 MPa. When the steel slag content (55%~60%, mass fraction) is high, the late compressive strength of steel slag solid waste cementitious materials is high. Under early CO₂ curing, the steel slag solid waste cementitious materials undergo carbonization reaction to form CaCO₃ crystals, which fill the pores and compact the microstructure. Some CaCO₃ participates in the hydration reaction in the later stage to form single carbon hydrated calcium carboaluminate. The steel slag solid waste cementitious materials with high steel slag content (>55%, mass fraction) and low desulfurized gypsum content (<15%, mass fraction) have lower linear expansion rate and autoclave expansion rate, and improve volume stability.

Mechanical Properties of Green Engineering Cementitious Composites with Tailing Sand as Aggregate

YU Jiexin, ZHU Yiting, ZHUANG Xu, CHEN Yushuang, ZHANG Guangda, XU Li

2025, 44(9):  3337-3346.  doi:10.16552/j.cnki.issn1001-1625.2025.0183

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The high proportion of cement used in traditional engineering cementitious composites (ECC) leads to high costs and high carbon emissions, hindering the industrial application of ECC in transportation infrastructure. To overcome these limitations, while ensuring the mechanical properties of ECC, tailing sand was used as an alternative aggregate with increased fly ash content to develop an economical and green tailing sand ECC. Nine groups of ECC specimens with different mix proportion were designed for uniaxial compression and uniaxial tensile tests, employing varying aggregate types (tailing sand, a mixture of tailing sand and quartz sand, quartz sand) and ratio of fly ash and cement content (2.4, 3.4, and 4.4) to investigate their effects on mechanical properties, microstructure, and material sustainability. The tests revealed the failure process and deformation characteristics of ECC under loading stages. The results indicate that tailing sand, due to the angular morphology and micro-aggregate effect, exhibits excellent tensile strength and tensile ductility. The fly ash content has a dual effect on mechanical properties: as the ratio of fly ash and cement content increases, both the tensile and compressive strengths of ECC decrease, while the ultimate tensile strain significantly improves. By comparing sustainability indicators with traditional ECC, the results demonstrate that the novel ECC with tailing sand as aggregate can effectively reduce costs, energy consumption, and carbon dioxide emissions. This study validates the sustainability of utilizing industrial solid waste tailing sand as aggregate to produce green ECC, providing guidance for the application of environmentally friendly tailing sand ECC.

Properties of Geopolymer-Stabilized Construction Solid Waste Recycled Aggregates

ZHANG Zhengqi, LIU Zhixin, RUI Zhaocheng, SHI Jierong, YANG Xinhong

2025, 44(9):  3347-3354.  doi:10.16552/j.cnki.issn1001-1625.2025.0185

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A geopolymer composite material was prepared using fly ash, ground granulated blast furnace slag, and alkali activator, which was then mixed with water-glass solution reinforcing recycled aggregate to produce geopolymer-stabilized recycled aggregate. Mechanical and drying shrinkage tests were conducted to investigate the effects of geopolymer content and recycled aggregate reinforcing on material properties. Additionally, SEM micromorphology analysis was performed to examine the reinforcing mechanism of recycled aggregate. The results indicate that the mechanical properties of geopolymer-stabilized recycled aggregate improve with increasing geopolymer content and age, achieving a performance comparable to cement-stabilized macadam, and are further enhanced by water-glass solution reinforcing. However, the drying shrinkage property of geopolymer-stabilized recycled aggregate increases with increasing powder (fly ash and ground granulated blast furnace slag) content, and the total drying shrinkage coefficient is slightly larger than that of cement-stabilized macadam. Nevertheless, water-glass solution reinforcing effectively mitigates drying shrinkage property. Microstructural analysis reveals that water-glass solution reinforcing treatment fills microcracks and pores on the surface of recycled aggregate, thereby enhancing the mechanical strength and drying shrinkage property of geopolymer-stabilized recycled aggregate to a certain extent.

Mechanism Study on Influences of Heat Treatment Temperature and Storage Time on Activity of Construction Waste Separation Residue

QIU Junfu, ZHANG Ruifeng, HE Xinxin, ZHAO Yuxiang, HU Jialei, LI Yaxi

2025, 44(9):  3355-3366.  doi:10.16552/j.cnki.issn1001-1625.2025.0337

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The complex composition and low reactivity of construction waste separation residue (CWSR) are the primary reasons hindering its resource utilization. Through X-ray fluorescence (XRF) analysis, thermogravimetric (TG) analysis, hydration heat analysis, nitrogen adsorption analysis, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) analysis, the influence mechanisms of different heat treatment temperatures and storage time on activity of construction waste separation residue were systematically investigated. The influence law of construction waste separation residue on the macroscopic properties and microstructure of ordinary Portland cement (OPC) binder systems under these conditions was further analyzed. The results indicate that the compressive strength and strength activity index of construction waste separation residue increase first and then decrease with increasing heat treatment temperature. When the heat treatment temperature is 500 ℃, its strength activity index meets the requirements for fly ash strength activity index specified in “Fly ash used for cement and concrete” (GB/T 1596—2017). The addition of construction waste separation residue prolongs the hydration induction period of ordinary Portland cement binder systems and delays the time of peak hydration exothermic rate during acceleration period. High-activity heat treatment construction waste separation residue generates hydration products in OPC-CWSR binder system which effectively fill pores within test specimens, enhancing compactness and endowing the binder system with improved mechanical properties and durability. When the heat treatment temperature is 500 ℃, the 28 d compressive strength of OPC-CWSR reaches 37.50 MPa, representing a 14.55% increase compared to OPC-CWSR binder system at a heat treatment temperature of 100 ℃, accompanied by a 75% reduction in total pore volume. In addition, compared with heat treatment temperature, storage time exhibits limited impact on CWSR activity but significantly influences the hydration process of OPC-CWSR binder systems.

Ceramics

Light Curing Molding of Barium Titanate/Calcium Silicate Piezoelectric Bioactive Composite Ceramics

QIU Haohong, BAO Chonggao, LI Shijia, DONG Wencai, YAN Shuo

2025, 44(9):  3367-3374.  doi:10.16552/j.cnki.issn1001-1625.2025.0229

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Piezoelectric bioactive composite ceramic materials can induce mineralization of bone-like components while generating electrical signals to stimulate osteoblast proliferation and differentiation, making them ideal bone repair materials, but there are still few related light curing molding. In this study, barium titanate/calcium silicate light curing composite ceramic slurries suitable for molding by digital light processing technology were successfully prepared, and the effects of main active monomers on the rheological and curing properties of slurries, as well as the effects of type and content of dispersants on the rheological properties of slurries were systematically investigated. The results show that 4-acryloylmorpholine (ACMO) is the most suitable main active monomer, and 3% (mass fraction) wetting dispersant BYK-111 is the most suitable dispersant system. When solid content is 50% (volume fraction), composite ceramic slurries exhibit favorable shear-thinning characteristics. Barium titanate/calcium silicate porous ceramic green bodies with complex structures can be printed using the above slurry, and barium titanate/calcium silicate composite ceramics with visible porosity of about 39.33% and flexural strength of (27.18±1.75) MPa are obtained after sintering at 1 110 ℃ for 4 h.

Plasma Melting Fabricated High Strength Al₂O₃-La₂O₃ Binary Ceramic Microspheres

HAO Hongyan, WU Yuesheng, XIE Jun, ZHANG Jihong, HAN Jianjun

2025, 44(9):  3375-3382.  doi:10.16552/j.cnki.issn1001-1625.2025.0188

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In order to overcome the limitations of traditional ceramic microspheres preparation methods in large-scale production and high-performance material applications, this study successfully prepared alumina-lanthanum oxide (Al₂O₃-La₂O₃) binary transparent ceramic microspheres with different proportion by spray granulation and radio frequency plasma melting based on phase diagram design. The chemical composition, morphology, microstructure and mechanical properties of Al₂O₃-La₂O₃ binary transparent ceramic microspheres with different proportion were studied. The results show that the main crystalline phases of the obtained Al₂O₃-La₂O₃ binary transparent ceramic microspheres are LaAlO₃ and LaAl₁₁O₁₈, and exhibit high mechanical properties. The Vickers hardness and elastic modulus of 80.0Al₂O₃-20.0La₂O₃ microspheres are 21.20 and 192 GPa, respectively, which are higher than those of other aluminate glass ceramics with different compositions.

Effect of Hot Pressing Pressure on Microstructure and Properties of Silicon Nitride Ceramics

ZANG Xiangrong, YU Zhiqiang, LI Haiqing, TAN Huihui, LU Yanping, PENG Zihan

2025, 44(9):  3383-3390.  doi:10.16552/j.cnki.issn1001-1625.2025.0186

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Silicon nitride (Si₃N₄) ceramics with high strength and toughness were prepared by hot pressing sintering process. The effects of hot pressing pressure on the phase composition, microstructure, mechanical properties and thermal conductivity of Si₃N₄ ceramics were studied. The results show that when the sintering temperature is 1 680 ℃ and the hot pressing pressure is between 20 MPa and 30 MPa, the α-Si₃N₄ is completely transformed into long rod-like β-Si₃N₄. With the increase of hot pressing pressure, the long-like β-Si₃N₄ grains developed completely, the porosity decreases, and the density increases. At the same time, in the process of hot pressing sintering, the grain growth of β-Si₃N₄ is oriented, and the crystal prism surface is perpendicular to the direction of hot pressing. When the hot pressing pressure is 30 MPa, the comprehensive performance of Si₃N₄ ceramics is the best, the bending strength is 1 123.72 MPa and the fracture toughness is 11.6 MPa·m^1/2, the Vickers hardness perpendicular to the hot pressing direction is 14.42 GPa, and the thermal conductivity at room temperature is 44.2 W/(m·K). By changing the content of single-phase sintering additives, the thermal conductivity of Si₃N₄ ceramics prepared by selecting Y₂O₃-MgO sintering additives under the same conditions is greatly improved, up to 62.9 W/(m·K).

Dynamic Mechanical Property and Constitutive Modeling of Sapphire Single Crystals

HUANG Youqi, SHI Liutong, GAO Yubo, ZHOU Lin

2025, 44(9):  3391-3401.  doi:10.16552/j.cnki.issn1001-1625.2025.0170

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Sapphire single crystals are widely used in protective windows for military equipment due to their excellent mechanical strength and optical transparency. To systematically investigate their dynamic mechanical behavior, a series of experiments and numerical simulations were conducted in this study. Quasi-static and dynamic compression tests were carried out to obtain the stress-strain response and to analyze strength to strain rate sensitivity. The Brazilian disk splitting test was performed to measure the tensile strength, and a triaxial confining pressure test was conducted to study the mechanical response of granular sapphire single crystals under high hydrostatic pressure. Based on the above experimental data, a material constitutive model was conducted, incorporating an equation of state, a strength criterion, and a damage evolution law. Ballistic high speed impact tests were further conducted, and a FEM-SPH coupling method numerical model was established to simulate the penetration process and crack propagation mechanisms. The results show that the constitutive model accurately captures the mechanical response of sapphire single crystals under various stress conditions, providing important guidance for the design of protective structures.

Glass and Refractory Materials

Redox Regulation of Batch Materials for Remelting Waste Photovoltaic Glass to Produce Ultra-Clear Glass

TIAN Yingliang, YUAN Zhichun, ZHAO Zhiyong, WU Yufeng

2025, 44(9):  3402-3410.  doi:10.16552/j.cnki.issn1001-1625.2025.0198

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With the large-scale decommissioning of photovoltaic modules in China, photovoltaic glass accounts for the largest part of module mass (≥70%), and its high-value and green recycling have become the key issue to be solved urgently for the sustainable development of new energy industry. This study innovatively proposed the remelting waste photovoltaic glass to produce ultra-clear glass and explored the regulatory mechanism of the Redox of batch materials on the optical properties of the recycled ultra-clear glass. The results indicate that enhancing the oxidative nature of batch materials can effectively improve the optical performance of the glass. When using NaNO₃, CeO₂+NaNO₃, and Na₂SO₄+carbon powder (C) to adjust the Redox of batch materials, the visible light transmittance of the glass increase from 91.00%, 90.61% and 87.89% to 91.33%, 91.46% and 91.57%, respectively, and the yellow-green hue of the glass is reduced. In particular, the Na₂SO₄+C has the most significant effect on improving the visible light transmittance and reducing the yellow-green hue. This study provides a theoretical basis and process optimization scheme for the closed-loop high-value utilization of decommissioned photovoltaic glass.

Influences of Clarifying Agents on Clarification Effect of OLED Substrate Glass

TIAN Yingliang, LI Zhifeng, ZHAO Zhiyong

2025, 44(9):  3411-3418.  doi:10.16552/j.cnki.issn1001-1625.2025.0192

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In the production of OLED substrate glass, stringent quality requirements are imposed, particularly for the melting and clarification processes of the batch materials. This study employed high-temperature observation technology to conduct in situ observation of the batch melting and glass melt clarification processes. The effects of three clarifying agents tin oxide, antimony trioxide, and barium sulfate as well as their doping concentrations on the clarification efficiency of OLED substrate glass were investigated. Using image analysis, the number and average diameter of residual bubbles in the glass melt after 4 h of heat preservation were quantitatively evaluated. The results demonstrate that tin oxide exhibits superior clarification performance compared to antimony trioxide and barium sulfate. The optimal clarification effect is achieved at the SnO₂ addition level of 0.5%(mass fraction), yielding only 22 residual bubbles.

Preparation and Properties of Coherent Silica Fiber Bundles Using Stack-and-Draw Method

XU Yantao, LYU Dajuan, CUI Xiaoxia, HOU Chaoqi, GUO Haitao, GAO Song, ZHANG Yan, SHE Shengfei

2025, 44(9):  3419-3425.  doi:10.16552/j.cnki.issn1001-1625.2025.0281

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Coherent silica fiber bundles (CSFBs) have important applications in the domains of medical endoscopy, flaw detection in industrial equipment, and novel types of optical systems due to their excellent flexible transmission of light and anti-electromagnetic interference characteristics. The relationship between the numerical aperture of optical fibers, cladding thickness, and energy leakage rate was investigated using COMSOL software, resulting in the optimization of a fiber structure characterized by a high filling factor and low crosstalk rate. The stack-and-draw process was studied. The results show that low-temperature drawing reduces the evaporation of the volatile element F, which is beneficial for suppressing the formation of defects. The high-resolution CSFBs are fabricated, featuring a single fiber diameter of approximately 4.4 μm, an outer diameter of the fiber bundle between 0.4 mm and 0.6 mm, a pixel count ranging from 1 500 to 15 000, the maximum theoretical resolution of approximately 131 lp/mm, and the optical loss of 0.1 dB/m in the visible spectrum by using a single stack process. The end face of the CSFBs exhibits no broken fibers or dark fibers, resulting in distortion-free imaging with high quality, thereby laying a foundation for the application of CSFBs.

Corrosion of Zirconia Refractory Materials by Molten Pharmaceutical Waste Salts

CHENG Weiwei, TIAN Yingliang, YANG Qinhao, ZHAO Zhiyong, XIE Junlin, HE Feng

2025, 44(9):  3426-3434.  doi:10.16552/j.cnki.issn1001-1625.2025.0284

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With the rapid development of the pharmaceutical industry, the annual production and accumulation of pharmaceutical waste salts in China have steadily increased. While the electrofusion method efficiently separates and purifies complex pharmaceutical waste salts, it causes severe corrosion to refractory materials, significantly affecting furnace longevity. In this study, according to the composition of pharmaceutical waste salt, the corrosion behavior and corrosion mechanism of molten salt on AZS41# and Z9510 refractory materials were studied by means of SEM, EDS, XRD and thermodynamic calculation. The results show that after corrosion at 950 ℃ for 48 h, neither of AZS41# and Z9510 refractory materials show an altered layer, with Ca element from the molten salts predominantly penetrating into the glass phase. After corrosion at 1 150 ℃ for 48 h, AZS41# sample forms an altered layer about 235 μm. There is no zircon phase and corundum phase in the altered layer, and the main enrichment elements are Na, Ca and Si. The Na(AlSi₃O₈) phase is formed after molten salt erosion refractory material. The Z9510 sample has a altered layer of about 54 μm, which is enriched with Na element, and two main phases of CaZrO₃ and Na(AlSi₃O₈) are formed after molten salt erosion. Therefore, in the long-term high-temperature molten salt environment, the corrosion resistance of Z9510 refractory material is more excellent.

Functional Materials

Preparation and Electrochemical Properties of Porous Carbon Fibers Derived from Cattail Fibers

WANG Chaonan, LI Xuefeng, WU Xinyue, YU Xiaoting, LI Jiali, YANG Limin, BAI Lizhong

2025, 44(9):  3435-3443.  doi:10.16552/j.cnki.issn1001-1625.2025.0181

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Supercapacitors have become one of the most promising energy storage devices due to their high power density, rapid charge and discharge speed and long cycle life. In this paper, low-cost and environmentally friendly porous carbon fibers have been successfully designed and synthesized from the high temperature carbonization and KOH activation of the natural cattail fibers. The structure, morphology and electrochemical properties of porous carbon fibers were characterized by XRD, SEM, Raman spectroscopy, N₂ adsorption desorption and electrochemical measurements. The alkali-carbon ratio can significantly affect the structures and properties of porous carbon fibers. The porous carbon fibers ACF-4, which are prepared under carbonization at 800 ℃ and alkali-carbon ratio of 4 ∶1 (mass ratio), have the highest specific surface area of 1 910.4 m²·g^-1 and the largest micropore volume of 0.548 cm³·g^-1. The ACF-4 exhibits a high specific capacitance of 254.9 and 156.0 F·g^-1 at a current density of 0.05 and 5 A·g^-1, respectively. After 10 000 cycles at a current density of 1 A·g^-1, the ACF-4 displays an outstanding cycling stability of 98.1% capacitance retention.

Ferroelectric and Photovoltaic Properties of BiFeO₃/BiCrO₃ Composite Thin Films

YANG Song, YANG Xunyong, LIU Yonglin, YI Yingfei, WANG Jianwei, WANG Xu

2025, 44(9):  3444-3450.  doi:10.16552/j.cnki.issn1001-1625.2025.0195

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BiFeO₃ thin films have attracted much attention for potential applications owing to their advantages of room-temperature multiferroic properties, controllable preparation process, and high remanent polarization. However, large leakage current density and wide band gap limit their application in practical devices. In this work, high quality BiFeO₃/BiCrO₃(BFO/BCO) composite thin films and their devices were obtained by sol-gel process, and the microstructural features, surface morphology, ferroelectric properties and optical response characteristics of the films were systematically investigated. The experimental results demonstrate that the BFO/BCO composite thin films exhibit a characteristic perovskite structure without detectable secondary phases. The films display a densely packed grain structure with crack-free morphology showing exceptional surface uniformity as confirmed by SEM measurement. Remarkably, the BFO/BCO composite thin films possess enhanced ferroelectric properties with a remnant polarization of 2P_r=12.64 μC/cm² and superior photovoltaic performance, achieving an open-circuit voltage of 0.55 V and short-circuit current density of 0.60 mA/cm². These combined characteristics position the BFO/BCO composite thin films as a promising absorption layer candidate for ferroelectric-photovoltaic solar cells.

Numerical Simulation of Interface Shape and Constitutional Supercooling on Heavily Phosphorus-Doped Czochralski Silicon with Ultra-Low Resistivity

MA Wuxiang, MEI Haotian, LI Xiaochuan, FAN Jixiang, WU Yanguo

2025, 44(9):  3451-3461.  doi:10.16552/j.cnki.issn1001-1625.2025.0172

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The production of heavily phosphorus-doped silicon single crystals with ultra-low resistivity is primarily constrained by constitutional supercooling induced by high-concentration doping and crystal-melt interface deformation during Czochralski growth. In this study, to investigate the persistent lattice mismatch observed at a crystal length of approximately 1 000 mm during production, simulations were performed using CGSIM finite element software. It was demonstrated that the lattice mismatch originated from the elevation of the crystal-melt interface and phosphorus impurity segregation. And an improvement was proposed. The results indicate that interface height can be reduced by lowering crystal rotation, growth rate, and melt gap, while increasing crucible rotation. Based on the constitutional supercooling criterion V/G (crystal growth rate V divided by melt temperature gradient G), crystal pulling is conducted with a reduced V value to mitigate supercooling effects. By applying optimized parameters, dislocation-free 8-inch (1-inch=2.54 cm) heavily phosphorus-doped silicon single crystals are successfully grown over 5 consecutive cycles. The measured resistivity ranges from 0.000 93 Ω·cm to 0.001 25 Ω·cm, further validating the simulation results.

Road Materials

Preparation of Porous Mg-Al-Based Layered Double Hydrotalcites Warm Mix Agent and Its Effect on Performance of Asphalt Mixture

XIE Jun, DU Yuyang, WU Shaopeng, LI Menglin, LI Chao

2025, 44(9):  3462-3471.  doi:10.16552/j.cnki.issn1001-1625.2025.0225

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Warm mix asphalt mixture is a road material with broad application prospects, but its insufficient low-temperature crack resistance and water stability performance limit its engineering applications. This study successfully prepared porous Mg-Al-based layered double hydrotalcites (SDS-LDHs) intercalated with sodium dodecyl sulfate (SDS) through hydrothermal synthesis and calcination restoration methods. The microstructure and water release behavior of SDS-LDHs were investigated using scanning electron microscopy (SEM) and thermogravimetric-differential scanning calorimetry (TG-DSC), and the optimal SDS-LDHs content was determined by Brookfield viscosity tests. The pavement performance of warm mix agent was further evaluated through high-temperature rut, semi-circular bending, and Hamburg rut tests. The results show that SDS-LDHs exhibit a three-dimensional porous structure with a water content of 13.64%. When incorporated SDS-LDHs into asphalt, they rapidly and uniformly release water, effectively reducing asphalt viscosity. With 2% (by asphalt mass) SDS-LDHs, the mix temperature and compaction temperature of warm mix asphalt mixture decrease by 20 and 15 ℃ respectively compared to hot mix asphalt mixture. Moreover, SDS-LDHs enhance the high-temperature performance stability and water stability of mixture by 36.0% and 51.4% respectively compared to hot mix asphalt mixture, while only reducing low-temperature fracture energy by 3.1%. SDS-LDHs not only absorb light components of asphalt but also chemically interact with siloxane groups on aggregate surfaces, thereby improving asphalt-aggregate adhesion and ultimately enhancing the pavement performance of warm mix asphalt mixture.

Effect of Asphalt/Cement Ratio on Fatigue Properties of Cement-Emulsified Asphalt Mortar

JIN Shanshan, LI Xiang, ZHANG Yang, LIU Pengfei, WANG Zhihua, LI Liuhuan, ZHAO Yaodong

2025, 44(9):  3472-3482.  doi:10.16552/j.cnki.issn1001-1625.2025.0317

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Cement-emulsified asphalt (CA) mortar, used as a cushion layer in ballastless track structures, is subject to fatigue damage under repeated wheel loading. In this study, the effects of stress ratio and asphalt/cement ratio on the fatigue life of CA mortar were investigated based on uniaxial compression test and fatigue test. The CA mortar fatigue life prediction equations incorporating stress ratios (0.6 to 0.8) and A/C (0.4 to 0.7) were constructed. The physical significance of equations was also elucidated, and finally the fatigue damage mechanism of CA mortar was revealed from a microscopic point of view. The results show that the growth rate of CA mortar compressive strength with age decreases as A/C increasing, asphalt gradually replaces cement hydration products as a continuous phase, and CA mortar properties approach those of asphalt mortar with enhanced toughness. The fatigue life of CA mortar gradually increases with increasing A/C under fatigue loading corresponding to the same stress ratio. The fatigue equation constructed with stress ratio and A/C as parameters can accurately predict the fatigue life of CA mortar with an average error of 6.9% between the predicting and actual values. The research results can provide a basis for predicting the fatigue life of CA mortar at a later stage.

Mechanical Properties of Fiber-Cement Improved Muck under Sulfate Erosion and Dry-Wet Cycle

TIAN Zhequan, LIU Tao, YU Liucheng, HUANG Xixi, ZHANG Yan, YI Xiangyang

2025, 44(9):  3483-3492.  doi:10.16552/j.cnki.issn1001-1625.2025.0243

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To investigate the deterioration effects of sulfate erosion and dry-wet cycle on fiber-cement improved muck, unconfined compression tests, scanning electron microscopy (SEM) tests, and X-ray diffraction (XRD) tests were conducted on fiber-cement improved muck. The study analyzed the impacts of dry-wet cycle and the coupled effects of sulfate erosion and dry-wet cycle on the morphological characteristics, mass loss rate, mechanical properties, and deterioration mechanisms of fiber-cement improved muck. The results indicate that as the number of dry-wet cycle increases, the mass loss rate of fiber-cement improved muck gradually increases, and the peak stress of fiber-cement improved muck decreases. Polyester fibers can effectively enhance the soil's resistance to the coupled effects of sulfate erosion and dry-wet cycle, with an optimal fiber content of 0.50% (mass fraction). Compared to the sole effect of dry-wet cycle, the coupled effect of sulfate erosion and dry-wet cycle leads to a more porous internal structure in fiber-cement improved muck and generates a significant amount of ettringite, ultimately resulting in a notable deterioration of mechanical properties.

Investigation on Evolution of Macro- and Micro-Polishing Properties of Aggregates Based on Differential Treatment

HAN Deming, YUAN Youhui, WANG Jintao, MA Dengke, ZONG Youjie, PENG Linwei, XIONG Rui

2025, 44(9):  3493-3502.  doi:10.16552/j.cnki.issn1001-1625.2025.0230

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Aggregate is the main component of asphalt mixture, and its polish resistance is closely related to the anti-skid performance of asphalt pavement. In this study, limestone and 88# calcined bauxite were blended in different volume ratios (0%, 25%, 50%, 75%, and 100%) to prepare polished specimens. An accelerated polishing machine was used to explore the changes in polished stone value (PSV), and the effects of different blending ratios on PSV were analyzed. The evolution of the micromorphology and arithmetic mean roughness S_a of the aggregate particle surface after differential polishing was explored through laser confocal microscopy, and the relationship between PSV and blending ratio, limestone S_a, and 88# calcined bauxite S_a was established. The research results show that in differential polishing, the attenuation law of PSV with the polishing cycle is quantitatively characterized. As the blending ratio of 88# calcined bauxite increases, the initial PSV and the final PSV gradually increase, but the improvement rate gradually decreases, the blending ratio range that has a significant impact on the final polishing value is 25% to 50%, as the blending ratio increases, the limestone surface S_a shows a fluctuating change that first decreases, then increases, and then decreases. Finally, the linear relationship between PSV and blending ratio, limestone S_a, and 88# calcined bauxite S_a was established.