Table of Content

Volume 44 Issue 12
15 December 2025

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Cement and Concrete

Research Progress on Preparation and Mechanical Properties of Recycled Aggregate Concrete

WANG Chunlong, MU Rui, LIU Ningbo, WANG Zhenggang

2025, 44(12):  4283-4300.  doi:10.16552/j.cnki.issn1001-1625.2025.0548

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As an eco-friendly building material, recycled aggregate concrete (RAC) has gained widespread application in engineering fields such as road construction and building structures due to its effective utilization of waste resources, shortened production cycles, reduced costs, and significant reduction in environmental impact, making it a crucial approach to addressing the excessive consumption of building materials. In light of this, this paper focused on the preparation methods, mechanical properties, and current state of engineering applications of RAC. It systematically reviewed the methodologies for the full-process preparation and performance optimization of RAC, providing an in-depth analysis of the intrinsic mechanisms that enhance its mechanical properties, and summarized its current application status in engineering practice. Furthermore, this paper prospected future research directions for RAC, aiming to provide valuable references for its large-scale research and application.

Effect of Portland Cement on Properties of Cement Adhesives Used in Large Tonnage Suspended Porcelain Insulators

ZHOU Weibing, MA Mingzhuo, ZHOU Jun, ZHAO Jiangtao, ZHOU Yongxin

2025, 44(12):  4301-4313.  doi:10.16552/j.cnki.issn1001-1625.2025.0565

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Portland cement adhesives represent a significant component of porcelain insulators, wherein the differences in the characteristics of the cementitious materials exert a significant influence on the performance of cement adhesives. In this study, Portland cements from Japanese Onoda cement and three domestic Portland cements were selected to analyze cement characteristics, and the effects of four Portland cements on the fluidity, setting time, mechanical properties, pore characteristics and thermal-mechanical properties of cement adhesives were investigated. The results show that domestic Portland cement adhesives exhibit superior performance in comparison with Onoda cement adhesive. The content of tricalcium aluminate (C₃A) in Taini cement is relatively high and average particle size of Taini cement is the lowest. This results in the formation of a greater quantity of ettringite (AFt), which subsequently fill the pores in the early stage of hydration, 3 d compressive strength and flexural strength of Taini cement adhesive reach 105.4 and 18.5 MPa, respectively. However, the production of alumino-ferrite-mono (AFm) during the later stages of hydration results in a high dry shrinkage rate. The content of C₃A and gypsum in China resources cement is low, and more hydrated calcium silicate (C-S-H) gel and AFt are produce in the later stages of hydration, with the lowest porosity (6.67%) and dry shrinkage rate (0.040% at 11 d) of China resources cement adhesive. The average particle size of Conch cement is relatively large and tricalcium silicate content is the highest, which results in a relatively high later strength Conch cement adhesive. However, due to the transformation of AFt to AFm in the later stage of hydration, the dry shrinkage rate of Conch cement adhesive is relatively high. The thermal-mechanical properties of porcelain components bonded with domestic Portland cement adhesives have all been shown to exceed those of the Onoda cement adhesive, indicating that the domestic Portland cement has the capacity to replace Onoda cement in the production of ultra-high voltage large tonnage porcelain insulators.

Effects of Different Types of Gypsum on Compatibility Between Portland Cement and Alkali-Free Liquid Accelerator

LI Xiaopeng, ZENG Fanchao, WANG Qin, WANG Jian, XU Kexin, GUO Zhixiang

2025, 44(12):  4314-4324.  doi:10.16552/j.cnki.issn1001-1625.2025.0563

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Different types of gypsum can affect the compatibility between cement and alkali-free liquid accelerators in shotcrete. This study compared the effects of anhydrite, hemihydrate, and dihydrate gypsum on the macroscopic properties of cement by examining cement paste setting time and mortar compressive strength, with the addition of alkali-free liquid accelerator. The mechanism by which gypsum type affects cement hydration was revealed using microstructural testing methods, such as heat of hydration testing, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The results indicate that, under the influence of an alkali-free liquid accelerator, the types of gypsum significantly impact the compatibility between cement and gypsum. The dissolution rates of gypsum decrease in the following order:hemihydrate, dihydrate, and anhydrite, with a lower dissolution rate contributing to a higher early heat release in the cement paste, thus accelerating the setting and hardening process. Moreover, the hydration of the cement becomes more complete, and a greater amount of calcium hydroxide and calcium silicate hydrate gel is produced in the hydration products, resulting in enhanced mechanical performance of the hardened mortar. However, the change of gypsum type in cement only affects the early hydration process and the microstructure of the hardened cement paste, with no significant impact on the mechanical properties, hydration products, and microstructure in the later stages of hydration. This study provides an important theoretical basis and practical reference for understanding the effects of different gypsum types on the compatibility between cement and alkali-free liquid accelerators.

Influence of Na₂SO₄ on Performance of Gas Sealing Composite Cement

ZHU Jiafeng, LIANG Xueyan, YANG Wenwang

2025, 44(12):  4325-4331.  doi:10.16552/j.cnki.issn1001-1625.2025.0615

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This paper investigated the effects of Na₂SO₄ on setting time, slump flow, hydration heat, expansion rate, compressive strength, and micromechanical properties of gas sealing composite cement (composed of ordinary Portland cement and sulphoaluminate cement). The results show that Na₂SO₄ accelerated the setting and hydration processes of composite cement, and its setting acceleration effect is positively correlated with the dosage (0.5%~2.0%, mass fraction). Meanwhile, both the expansion rate and compressive strength of composite cement increase with the increase in Na₂SO₄ dosage. By incorporating 0.5%~2.0% Na₂SO₄, the increase rates of compressive strength of the composite cement are 23.3%~100.0% (1 d), 10.4%~30.8% (3 d), 6.8%~23.9% (7 d), and 11.0%~29.9% (28 d). Micromechanical property analysis indicates that the hydration of composite cement is more complete, with a more uniform distribution of elastic modulus and a notable increase in the formation of gel-like products with low elastic modulus. These findings provide a technical basis for performance regulation of high-performance gas sealing materials.

Mechanical Properties of PET Fiber Composite Mortar Based on Response Surface Optimization

HUANG Qiang, ZHANG Yongcheng, CAO Feng, REN Huichao

2025, 44(12):  4332-4345.  doi:10.16552/j.cnki.issn1001-1625.2025.0570

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In order to solve the problems of shrinkage and cracking of cement-based materials and recycling of polyethylene terephthalate (PET) waste, and to prepare PET fiber reinforced cement composite cementitious materials with good toughness and excellent work performance and mechanical properties, the central composite design (CCD) in response surface methodology (RSM) was used to establish a regression model. The effects of fly ash (FA), magnesium oxide expansive agent (MEA) and PET fiber composite additive on the work performance (fluidity) and mechanical properties (flexural strength, compressive strength and flexural-to-compression strength ratio) of cement mortar and their synergistic effects were systematically studied. The reliability of the regression model is verified by variance analysis, and multi-objective optimization is carried out based on the desirability function. The results show that the fluidity is mainly affected by FA content (A) and PET fiber content (C), and the antagonistic effect of AC interaction is significant. The flexural strength is mainly affected by A and C, and the synergistic effect of AC is significant. The compressive strength is affected by the combined regulation of A, MEA content (B) and C, and the interaction between AC and AB is significant. The flexural-to-compression strength ratio is significantly affected by the synergistic effect of A and B. Three groups of optimal mix ratios are obtained by multi-objective optimization and the verification test is carried out. The relative errors between the predicted values and the measured values of each index are less than 5%, indicating that the regression model can be effectively applied to the optimal design of the mix ratio of PET fiber reinforced cement composite cementitious materials, which provides an empirical reference for the multi-objective optimization of cement-based composites.

Mesoscopic Simulation Study on Splitting Tensile Damage Process of Orthoconcrete

HAN Jin, SUN Jiangtao, LI Zhitang, HUANG Sheng, SHEN Weiguo, ZHAO Qinglin

2025, 44(12):  4346-4358.  doi:10.16552/j.cnki.issn1001-1625.2025.0623

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In order to investigate the damage characteristics of the splitting and tensile process of orthoconcrete, a three-dimensional five-phase mesoscopic model was established, which included mortar, aggregates, the interfacial transition zone of the outer surface of reference aggregates, the interfacial transition zone of the outer surface of post-filling aggregate and pores. The effect of mesh size on the final failure mode and stress-strain relationship of concrete were studied, and the effects of coarse aggregate filling rate and aggregate particle size on the splitting tensile properties of concrete were analyzed. The results show that when the mesh size is 1.0 mm, the model can effectively simulate the crack morphology and stress-strain relationship of splitting tensile damage of orthoconcrete. The splitting tensile strength of orthoconcrete increases first and then decreases with the increase of filling rate, and reaches the maximum when the post-filling rate is 20% (volume fraction). When the filling rate is constant, the splitting tensile strength of orthoconcrete with 16~31.5 mm filling aggregate is higher. The comparison between simulation and experimental results reveal low the error value, which indicates that the proposed mesoscopic model can successfully simulate the damage behavior of orthoconcrete under splitting tensile stress.

Effect of Fiber Orientation Distribution on Flexural Properties of UHPC

ZOU Hua, LI Shuichang, LAO Jiakun, LIU Ping

2025, 44(12):  4359-4367.  doi:10.16552/j.cnki.issn1001-1625.2025.0562

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To investigate the influence of steel fiber orientation on the flexural performance of ultra-high performance concrete (UHPC), an electromagnetic coil was developed to generate a uniform magnetic field, and the characteristics of its internal field distribution were analyzed. Directional steel fiber UHPC was prepared using magnetic field-induced alignment. The fiber orientation was quantitatively evaluated using CT scanning and 3D image reconstruction. Four-point bending tests were conducted on UHPC with different fiber volume fractions (0%, 0.5%, 1.0%, 1.5% and 2.0%) and fiber lengths (10, 13, 16 and 20 mm) for fiber orientation distribution and randomly distribution. Additionally, the effects of different parameters on load-deflection behavior, flexural strength, and toughness were investigated. The results indicate that after magnetic field induction, the fibers are predominantly aligned along the target direction, achieving a fiber orientation coefficient of up to 0.882 or greater. The flexural strength and toughness of directional steel fiber UHPC increase by 68.6%～125.7% and 68.2%～325.1%, respectively. The optimal strengthening effect is observed at a fiber length of 13 mm and a volume fraction of 1.5%. Compared with randomly distribution fiber UHPC, under equivalent flexural strength, the fiber content in directional steel fiber UHPC is reduced by more than 50%.

Powder Water Demand Index and Its Application of Manufactured Sand

WU Wenzhen, SUN Jiangtao, LI Zhitang, SHANG Yixin, ZHANG Wentao, XU Wei, SHEN Weiguo

2025, 44(12):  4368-4374.  doi:10.16552/j.cnki.issn1001-1625.2025.0529

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In order to evaluate the water demand of powder in manufactured sand (MS) quantitatively, a powder water demand index (WDI) as well as its measurement and calculation method was proposed. The influence factors of the WDI of manufactured sand powder were explored, and the relationship between WDI and the workability and mechanical properties of concrete was investigated. The results indicate that the workability and mechanical properties of concrete decrease with the increase of WDI. The correlation coefficient between WDI and slump flow is 0.86, and the correlation coefficient between WDI and compressive strength is 0.88, indicating a good correlation. The manufactured sand mixed with different clay minerals has higher correlation between WDI and concrete workability, while the correlation with strength is slightly lower, therefore, the significant correlation between WDI of MS and MS concrete performance indicate WDI can be used as a classification indicator. Finally, the limitations and improvement technical routs of WDI formula are proposed.

Solid Waste and Eco-Materials

One-Part Geopolymer Prepared by Solid Composite Activator

WANG Zhanpeng, WANG Xin, QI Le, HU Ping, YANG Tao, ZHUANG Peizhi

2025, 44(12):  4375-4383.  doi:10.16552/j.cnki.issn1001-1625.2025.0593

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Sodium silicate solution is commonly used as a liquid activator for geopolymer preparation, but its high alkalinity, high viscosity, and it is not conducive to the on-site mixing and preparation of geopolymer slurry. In this study, a one-part geopolymer was synthesized using solid composite activators including NaOH, Ca(OH)₂, and Na₂CO₃ to co-activate fly ash-slag blends. The influences of alkalinity and fly ash content on the fluidity of fresh paste and the compressive strength of hardened binder were systematically investigated. The hydration products and microstructure were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and pore structure analysis. The results indicate that with the increase of fly ash content, paste fluidity increases, setting time prolongs, and compressive strength decreases. The highest 28 d compressive strength (48.8 MPa) is achieved at 6% (mass fraction) alkalinity and 20% (mass fraction) fly ash content. Higher activator alkalinity enhances the degree of alkali-activation reaction, promotes Ca²⁺ ions leaching from slag, increases the Ca/Si molar ratio of sodium-containing calcium aluminosilicate hydrate (C-(N)-A-S-H) gel phase, and reduces the total porosity to obtain a denser microstructure. An increase in fly ash content decreases the reaction degree, lowers the Ca/Si molar ratio and significantly increases the total porosity.

Influence of Shale Ceramsite on Properties of High Ductility Geopolymer Composites

WANG Zhaohui, WANG Shanwei, WANG Jie, HAN Yantong, DAI Haoyu

2025, 44(12):  4384-4394.  doi:10.16552/j.cnki.issn1001-1625.2025.0522

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Shale ceramsite (SC), functioning as a lightweight, porous aggregate with moderate strength, serves as intentional defects in geopolymer composites to induce saturated cracking behavior within the matrix. This study designed and fabricated 9 groups of high ductility geopolymer composite (HDGC) specimens with varying SC content and particle size distributions. Uniaxial compression tests, tensile tests, scanning electron microscopy, and energy-dispersive spectroscopy analyses were conducted at different curing ages to investigate the effects of SC content and particle size distribution on HDGC’s compressive strength, tensile strength, tensile strain, crack morphology, and microstructure. Results show that there is an interface reaction between SC and the matrix, and as the SC particle size decreases, the microstructure of SC-matrix interfacet is more compact. With the increase of SC content, the tensile strength and tensile strain of HDGC initially increase and then decreast. Whereas these properties generally decrease with the increase of SC particle size. Notably, the tensile strength and ultimate tensile strain of HDGC with 40% (mass fraction) SC and particle size distribution of 0.15~<0.30 mm achieve 5.8 MPa and 9.3%, respectively. This study can provide a theoretical reference for the design and application of green high-performance geopolymer composites.

Frost Heave and Thaw Settlement Characteristics of Metakaolin-Based Geopolymer Modified Soil

FAN Houchao, ZHU Jie, WU Haibo, ZHANG Zhonglun, YAN Zigang, LI Lin, TANG Wencheng

2025, 44(12):  4395-4405.  doi:10.16552/j.cnki.issn1001-1625.2025.0618

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Geopolymer is a kind of inorganic cementitious material formed by the process of depolymerization, monomer reconstruction and polycondensation reactions under alkali activation with solid industrial waste rich in aluminosilicate as precursor, which can be used to replace cement in treating weak soil layers. In order to study the frost heave and thaw settlement characteristics of geopolymer modified soil, metakaolin-based geopolymer was used to treat marine sedimentary silty clay in Fuzhou. The frost heave and thaw settlement tests of the modified soil were conducted under different levels of multiple factors, including curing age, cold end temperature, activator modulus, sodium silicate to metakaolin (S-MK) mass ratio and geopolymer content. The results show that the frost heave and thaw settlement characteristics of the modified soil are significantly weakened. The frost heave rate and thaw settlement coefficient decrease with the increase of curing age and geopolymer content, and improve with the increase of activator modulus and S-MK mass ratio. When the cold end temperature decreases, both of them reduce linearly. Through comparison, it is found that the frost heave rate and thaw settlement coefficient of geopolymer modified soil are significantly lower than those of cement modified soil under the same geopolymer content.

Influence of Kaolinite Content on Performance of Limestone-Calcined Clay-Cement

WANG Qing, SHAN Rui, LI Tianru, ZHANG Qiang, CHENG Yang, ZHAO Mingyu

2025, 44(12):  4406-4412.  doi:10.16552/j.cnki.issn1001-1625.2025.0489

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Two calcined clay minerals (namely coal gangue and metakaolin) were blended to adjust the kaolinite content in calcined clay. This process was employed to prepare limestone-calcined clay-cement (LC³) with 50% (mass fraction) clinker content. The mechanical property and hydration product evolution of LC³ with calcined clay containing 20% to 90% (mass fraction) kaolinite were investigated using a variety of analytical techniques, including compressive strength tests, hydration exothermic analysis, X-ray diffraction (XRD), thermogravimetric analysis (TG), and thermodynamic simulations. The results show that the increase of kaolinite content promotes the reaction between calcium carbonate and aluminate in calcined clay, and consumes calcium hydroxide and ettringite generated during the hydration of cement clinker. When the content of kaolinite increases from 20% to 60%, the mechanical properties of LC³ gradually increase, and the 28 d compressive strength increases by 33.99%. The amount of C-(A)-S-H gel, ettringite and carboaluminate in hydration products increases, and the degree of clinker reaction decreases from 89.09% to 82.08%. When the kaolinite content exceeds 60%, with the further increase of kaolinite content, the decrease of clinker reaction degree and the increase of compressive strength obviously slow down, and the 28 d compressive strength only increases by 2.77 MPa. The content of carboaluminate in hydration products increases, but the increase is relatively limited. At the same time, the thermodynamic simulation results show that the content of C-(A)-S-H gel decreases.

Optimization of Preparation Process for Fly Ash-Steel Slag Based Ceramic Tiles

JI Ying, SU Huxiong, LIU Baolin, CHEN Huan, LIU Shibin, WU Jiarui

2025, 44(12):  4413-4424.  doi:10.16552/j.cnki.issn1001-1625.2025.0496

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The main raw materials of this study were steel slag and fly ash, with quartz sand as the auxiliary material. Based on the synergistic effect of steel slag and fly ash, fly ash-steel slag (CaO-MgO-SiO₂-Fe₂O₃-Al₂O₃) based ceramic tiles were prepared. The effects of raw material ratios and process parameters such as molding pressure (15~35 MPa), sintering temperature (1 165~1 190 ℃), and holding time (30~60 min) on the physical and mechanical properties of ceramic tiles were investigated. The results show that the optimal mass ratio is m₁(steel slag)∶ m₂(fly ash)∶ m₃(quartz)=9∶8∶4, and the influence of fly ash content is the most significant. The density of the ceramic body is the best at a molding pressure of 25 MPa, and excessive pressure led to crystal fracture. The diffraction peak intensity is the highest, the fracture modulus is the largest, and the water absorption is the lowest at a sintering temperature of 1 180 ℃. The grain arrangement is the densest and the mechanical properties are the best at a holding time of 60 min. Under the optimized process (25 MPa molding pressure, sintering at 1 180 ℃ and holding for 60 min), porcelain tiles with gehlenite (Ca₂Al(AlSi)O₇) and diopside (CaMgSi₂O₆) as the main crystal phases are prepared, with a fracture modulus as high as 69.86 MPa and a water absorption as low as 0.12%.

Effect of Spent Waterglass Foundry Sand on Performance of Alkali-Activated Slag Material Mortar

SUN Fang, QIAO Maimai

2025, 44(12):  4425-4435.  doi:10.16552/j.cnki.issn1001-1625.2025.0587

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In this study, spent waterglass foundry sand (SwFS, denoted as SwFS₁ and SwFS₈, respectively) with two heat treatments of 100 and 800 ℃ were prepared to explore effect of SwFS on the properties of alkali-activated slag material (AASM) mortar. The results show that the solubility and content of dry waterglass coating (DWC) in SwFS determine the overall performance of AASM mortar, and both SwFS can increase the fluidity of AASM mortar. In particular, SwFS₁ with high solubility can accelerate the formation of hydration products and effectively refine the pore structure, thus significantly improving the micro-mechanical properties of AASM mortar. Due to the complexity of the interlayer interface, the compressive strength of AASM mortar increases first and then decreases with the increase of SwFS₁ content. When the SwFS₁ content is 60% (mass fraction), the compressive strength is the best, and the 3, 7 and 28 d compressive strength increases by 44.5%, 41.0% and 49.4%, respectively. Compared with SwFS₁, the solubility of SwFS₈ is lower, and enhancement effect of SwFS₈ on the compressive strength of AASM mortar is weakened. However, the hardened shell formed after DWC calcination enhances the elastic modulus of the interfacial transition zone (ITZ) in the sandwich-like interface, so that the compressive strength of AASM mortar with 100% (mass fraction) SwFS₈ is slightly higher than that of the control group, and the compressive strength increases by 9.1 % at 28 d.

Roasting Modification-Leaching Recovery of TiO₂ from Paper Sludge

LI Na, DING Xilou, JIA Yong, MENG Guanhua

2025, 44(12):  4436-4447.  doi:10.16552/j.cnki.issn1001-1625.2025.0442

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In this paper, titanium-containing paper sludge was utilized as the raw material for the recovery of titanium dioxide (TiO₂) through a combined process of sodium carbonate mixed roasting-two stage acid leaching-ammonium hydrogen fluoride (NH₄HF₂) leaching. The effects of key parameters such as roasting temperature, mass ratio of Na₂CO₃ to paper sludge, H₂SO₄ concentration and NH₄HF₂ concentration on the recovery rate and purity of TiO₂ were systematically investigated. The results show that under the roasting temperature of 850 ℃, mass ratio of Na₂CO₃ to paper sludge of 0.7∶1.0 and roasting time of 120 min, the optimal recovery effect of TiO₂ is achieved through a first acid leaching (acid leaching temperature is 70 ℃, H₂SO₄ concentration is 3.0 mol/L, liquid-to-solid ratio is 5∶1, acid leaching time is 60 min), second acid leaching (acid leaching temperature is 50 ℃, H₂SO₄ concentration is 1.5 mol/L, liquid-to-solid ratio is 5∶1, acid leaching time is 60 min), and NH₄HF₂ leaching (NH₄HF₂ concentration is 90 g/L, liquid-to-solid ratio is 5∶1, leaching time is 60 min, leaching temperature is 60 ℃). Under these conditions, the TiO₂ recovery rate is 81.20%, and the purity is 94.85%. The process destroys the phase structure of titanium-oxygen compounds and silicates by high-temperature roasting of sodium carbonate. Combined with acid leaching and NH₄HF₂ leaching, the efficient separation of titanium is realized, which provides a theoretical reference for the resource utilization of titanium-containing paper sludge.

Design Method of Solid Waste Concrete Traffic Noise Barrier Unit Panel

CAO Fang, LI Gang, GUO Jiashun, HU Chao, ZHANG Feilong, YAN Jiali

2025, 44(12):  4448-4457.  doi:10.16552/j.cnki.issn1001-1625.2025.0643

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The use of solid waste materials to manufacture noise barriers contribute to the two environmental protection fields of noise prevention and solid waste treatment, so has received increasing attention. This study proposed a solid waste traffic noise barrier unit panel made from waste soil generated during highway construction, and carried out related material research and development, structural design, and performance testing, including: based on machine learning technology, the mix proportion of frame material and sound absorption screen material was optimized respectively; the finite element software was used to analyze the stress of different structural schemes of the noise barrier unit panel; the acoustic performance of the trial-produced sound barrier unit panel sample was tested. The results show that through mix proportion optimization, the 28 d compressive strength of frame work material reaches 57.40 MPa, the 28 d flexural strength reaches 8.71 MPa, and the waste soil content reaches 18.00% (mass fraction). The sound absorption coefficient of the sound absorption screen material reaches 0.70, the weighted sound insulation index reaches 37.56 dB, and the waste soil content reaches 31.40% (mass fraction). Both materials achieve a high level of in performance and waste soil utilization at the same time. The grid-patterned structure exhibits optimal mechanical properties in both vertical and horizontal compressive strength. The noise barrier unit panel meets or exceeds the relevant national standards in both acoustic performance and durability.

Mechanical Properties and Microstructural Evolution of Clay-Based Foamed Lightweight Soil under Dry-Wet Cycles

ZHU Jie, ZHANG Zhihua, LIU Dongrui, YIN Chen, ZHANG Rongjun, ZHANG Bailing

2025, 44(12):  4458-4468.  doi:10.16552/j.cnki.issn1001-1625.2025.0582

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Aiming at the problem of the high cement content of conventional foamed lightweight soil (FLS), a low-carbon FLS was developed by replacing cement with high proportions of clay and ground granulated blast furnace slag. Under the conditions of different wet densities (6~10 kN/m³) and water content (115%~140%), effects of dry-wet cycles on the mechanical properties of FLS were investigated, and the microstructural evolution of FLS before and after dry-wet cycles was analyzed using scanning electron microscopy (SEM). The results show that the unconfined compressive strength of FLS continues to increase with curing age, but the decrease of wet density or the increase of water content significantly weaken the growth trend of unconfined compressive strength. When the wet density is 8 kN/m³ and the water content is 115%, FLS can balance both flow value and strength requirements for embankment filling. After 10 dry-wet cycles, FLS shows no obvious cracking or disintegration in the appearance, and the loss of unconfined compressive strength is less than 15%, and the E50 decreases by 16.8% to 24.4%, demonstrating good durability under dry-wet cycles. The SEM results show that dry-wet cycles lead to microcracks and localized fragmentation on the pore walls of spherical gas bubbles, with crack widths ranging from 5 to 20 μm. The FLS with low wet density and high water content is more susceptible to damage by reducing pore wall thickness and weakened soil particle bonding. However, the temperature-enhanced pozzolanic reaction effectively alleviates microstructure degradation and maintains high structural durability.

Effect of Biochar on Performance of Phosphorus Building Gypsum

WANG Wei, CHEN Xuemei, DENG Xianghai, LUO Li, WU Qihong, XIAO Linyi, KANG Hechuan

2025, 44(12):  4469-4479.  doi:10.16552/j.cnki.issn1001-1625.2025.0526

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To investigate the application potential of biochar in phosphogypsum-based cementitious materials, this study used corn stover biochar (CSB) and bamboo biochar (BB) to modify phosphorus building gypsum (PBG) under acidic and alkaline condition, respectively. The effect of biochar on the workability, mechanical properties and water resistance of PBG was examined through tests on fluidity, setting time, hydration heat, strength, water absorption rate and softening coefficient, combined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The results show that biochar significantly reduces the fluidity of PBG. When the biochar content is 5.0% (mass fraction, the same below), CSB and BB reduce the fluidity by 8.3% and 7.8% under acidic condition, respectively, and decrease the fluidity by 13.7% and 12.4% under alkaline condition, respectively. Biochar changes the hydration heat release process of PGB, thereby influencing setting time of PBG. When the biochar content is 5.0%, CSB and BB extend the setting time by 11 and 9 min under acidic condition, respectively, and CSB extends the setting time by 12 min and BB shortens setting time by 10 min under alkaline condition. XRD and SEM analyses reveal that biochar does not change the composition of hydration products of PBG but reduces the aspect ratio of CaSO₄·2H₂O crystals, thereby influencing the performance development of PBG. When the content of biochar is low (≤1.0%), CSB and BB have negligible effects on the flexural strength, compressive strength and water resistance of PBG under acidic condition, but improve the performance of PBG under alkaline condition. Among them, the compressive strength of PBG with 1.0% CSB content increases by 7.1%, and the water resistance is also improved. However, the flexural strength, compressive strength and water resistance of PBG significantly reduce when the content of biochar is high (>1.0%).

Influence Mechanism of Phosphogypsum on Mechanical Properties and Impermeability of Soft Clay Solidified with Slag-Cement Cementitious System

SUN Tao, LIU Yue, WANG Ziyan, OUYANG Gaoshang, QIN Tingxuan

2025, 44(12):  4480-4491.  doi:10.16552/j.cnki.issn1001-1625.2025.0541

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Soft clay has a high moisture content, high plasticity and extremely low strength, which can easily cause engineering hazards such as foundation instability and settlement. This study used a stabilizer composed of phosphogypsum, slag and ordinary Portland cement to solidify high moisture content soft clay. By gradually replacing the inert stone powder in the soil stabilizer with equal amounts of phosphogypsum, a univariate study of phosphogypsum was conducted to investigate its role in the system. Firstly, the microstructure evolution of solidified soil was studied based on pH test, X-ray diffraction test, scanning electron microscopy test and thermogravimetric test to determine the solidification mechanism. Secondly, the effect of phosphogypsum mass proportion in the stabilizer on the mechanical properties and impermeability of the solidified soil was studied through unconfined compressive strength test, direct shear test and permeability test. The results show that the main hydration products of the stabilizer are calcium (alumino) silicate hydrate (C-(A)-S-H) gel and ettringite. Phosphogypsum increases the hydration degree of the stabilizer and promotes the formation of ettringite in the system by stimulating the sulfate excitation effect on slag. The cementation of gel and the expansion and filling of ettringite jointly improve the mechanical properties and impermeability of solidified soft soil. With the gradual increase in the mass proportion of phosphogypsum in the stabilizer, the unconfined compressive strength and shear strength of the solidified soil are significantly enhanced. Under the optimal ratio conditions, it meets the usual acceptance criteria for soft soil foundation reinforcement, and the permeability coefficient is decreased by an order of magnitude (from 10^-7 to 10^-8).

Workability of Fluid Soil Solidified with Cement Synergistic Industrial Solid Waste

DAI Hengjun, WU Guangxiong, LI Haifeng, ZHOU Xue, ZHANG Rongjun

2025, 44(12):  4492-4502.  doi:10.16552/j.cnki.issn1001-1625.2025.0620

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In order to achieve the resource utilization of engineering muck and solve the problems of high carbon emission and poor solidification of traditional cement solidified materials, the composite binders composed of industrial solid waste and cement was used to carry out solidifying treatment of engineering muck. Comparative analysis of cement-ground granulated blast furnace slag (OPC-GGBS), cement-phosphogypsum, cement-fly ash three kinds of composite binder curing performance, preferred working performance of the composite binder combinations and proportion parameters, and further combined with the fluidity test, field emission scanning electron microscope (FSEM) test to explore the initial water content, binder content and the water-cement ratio of the influence rule of the workability of the fluid solidified soil. The result shows that: the mechanical properties of OPC-GGBS fluid solidified soil are relatively excellent, with an optimal mass ratio of OPC to GGBS of 50∶50. The effect of binder content on the fluidity of the fluid solidified soil at the early stage of the process is relatively low. With the increase of the initial water content or the decrease of binder content, the strength of the OPC-GGBS fluid solidified soil decreases significantly, while the flow value shows the opposite trend. The correlation fitting functions for the strength and flow value of OPC-GGBS fluid solidified soil with respect to water-cement ratio are established. With increasing water-cement ratio, the strength decreases in a power function trend, while the flow value increases linearly. FSEM image analysis shows that reducing the initial water content or increasing binder content can increase the production of cementitious materials, such as calcium silicate (aluminate) hydrate (C-(A)-S-H), in the fluid solidified soil, and reduce the pore volume.

Ceramics

Effect of La₂O₃ Doping on Curing and Mechanical Properties of ZTA Ceramics Fabricated by Digital Light Processing 3D Printing

YE Wenfeng, SUI Xiaoxiao, YU Jinyang, ZHANG Yanzhao, ZHOU Guoxiang, YANG Zhihua

2025, 44(12):  4503-4516.  doi:10.16552/j.cnki.issn1001-1625.2025.0556

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La₂O₃ doped zirconia toughened alumina (ZTA) ceramics were prepared using digital light processing (DLP) 3D printing technology, and the effect of La₂O₃ content on the viscosity, curing properties, microstructure, and mechanical properties of ZTA ceramic slurry was systematically investigated. The results show that the nano La₂O₃ powder reduces the UV absorption of ZTA ceramic powder, effectively reducing the viscosity of slurry system. The low absorbance of La₂O₃-ZTA promotes the curing of ZTA ceramic slurry and increases curing size, promoting the formation of micrometer sized pores. When content La₂O₃ is 0.6%(mass fraction), the minimum pore size of the sintered body reaches (71±3) μm, and LaAl₁₁O₁₈ and MgAl₂O₄ phases precipitate inside ceramics produce pinning effects, promoting the densification process of ceramic sintering and improving mechanical properties. The Vickers hardness, flexural strength, and fracture toughness of the ceramics are (1 625.2±16.5) Hv, (444.7±15.5) MPa, and (5.15±0.07) MPa·m^1/2, respectively, which are 10.55%, 21.07%, and 34.11% higher than the undoped component respectively. ZTA ceramics prepared using 3D printing technology have mechanical properties comparable to dry pressed products, while achieving micrometer level circular through-hole forming, breaking through the limitations of existing 3D printing ceramic technology in microstructure manufacturing.

Fabrication of Continuously Gradient Si₃N₄/SiC Composite Ceramics via Pseudo Hot Isostatic Pressing

HE Yanbo, HU Lanxin, TONG Yingxuan, ZHANG Yunshan, AN Chengbo, SHI Yunwei, HE Qianglong, WANG Weimin

2025, 44(12):  4517-4525.  doi:10.16552/j.cnki.issn1001-1625.2025.0535

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To solve the interfacial thermal expansion coefficient mismatch problem in traditional functionally gradient ceramics, a new method for fabricating continuously gradient Si₃N₄/SiC composite ceramics via PHIP was proposed. By combining gas-phase gradient diffusion with in-situ chemical reactions, the continuous gradient Si₃N₄/SiC composite ceramics were successfully prepared using a single powder system under uniform thermal field. The results show that gradient ceramics exhibit the phase composition characteristics of high α-Si₃N₄ content at the edge and high β-Si₃N₄ content inside. The microstructure is manifested as a high proportion of small-sized granular grains at the edge and a high proportion of large-sized rod-shaped grains inside. The Vickers hardness gradually decreases from the edges toward the interior, from 20.17 GPa to 17.56 GPa. Different nano-SiC content (5%, 10%, 20%, volume fraction) significantly influences gradient layer thickness, where the gray-green hard layer thickness increasing from 128 μm to 258 μm as the SiC content increases.

Preparation and Properties of Foam Ceramics from Coal Gasification Slag

ZHANG Bo, WU Jinzhao, ZHANG Qian, JIANG Haijin, BAI Pengcheng, LI Le, HUANG Wei

2025, 44(12):  4526-4535.  doi:10.16552/j.cnki.issn1001-1625.2025.0462

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This study utilized coal gasification slag as the primary raw material to prepare foam ceramics via the high-temperature foaming method. The effects of sintering temperature, holding time and SiC addition on the pore structure and properties of samples were investigated. The foaming and pore-forming mechanisms were also explored through the morphological changes and thermogravimetric analysis of the green body. The results show that when the sintering temperature is 1 100 ℃, the melt viscosity is too high and the porosity is only 78.7%. When the sintering temperature is 1 150 ℃, the pores become interconnected and the compressive strength decreases to 0.32 MPa. When the holding time is extended to 60 min, the average pore size increases to 3.29 mm and the compressive strength decreases to 0.48 MPa. When the SiC addition exceeds 0.6% (mass fraction), the pore coalescence is intensified. When the SiC addition is 1.2%, the sample bulk density rises back to 0.257 g/cm³. The optimized process parameters are determined to be a sintering temperature of 1 110 ℃, a holding time of 30 min, and a SiC addition of 0.6%. Foam ceramics prepared under these conditions have an uniform pore size, a bulk density of 0.457 g/cm³, a porosity of 81.5%, a compressive strength of 1.33 MPa, and an average pore size of 1.70 mm. The analysis indicates that before the green body reaches the dry shrinkage temperature, the gases are mainly produced by the residual carbon and calcite in coal gasification slag. After the sintering temperature reaches 1 000 ℃, the foaming is transformed into the decomposition of Fe₂O₃ and the oxidation of SiC. Meanwhile, under the action of alkali metals, the SiO₂ protective film is eroded, which promotes the diffusion of oxygen into the melt, thus enabling the continuous growth of bubbles.

Property of Lithium Tailings Foamed Glass-Ceramics Prepared by High-Temperature Foaming with Fe₂O₃ and SiC

YU Jinjun, GE Xuexiang, TANG Guanglong, JI Yongfa, JIN Yu, ZHONG Zhanfa, GE Tao, DAI Yonggang

2025, 44(12):  4536-4545.  doi:10.16552/j.cnki.issn1001-1625.2025.0551

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In this study, formed glass-ceramics using lithium tailings as primary raw material and silicon carbide (SiC) as the high-temperature foaming agent were prepared. The influence of iron oxide (Fe₂O₃) as an oxidation aid on the sintering behavior, pore structure, and physical properties of the foamed glass-ceramics was systematically examined. High-temperature microscopy, XRD, SEM and other microscopic characterization methods were employed to elucidate the underlying mechanisms by which Fe₂O₃ modifies the properties of the formed glass-ceramics. The results demonstrate that the incorporation of Fe₂O₃ significantly alters the color of the foamed glass-ceramics and influences their high-temperature foaming capability, pore structure, and physical properties. Fe₂O₃ facilitates the oxidation decomposition of SiC during the high-temperature foaming stage by supplying active oxygen (O^2-), thereby improving the high-temperature foaming ability of green body. At an optimal Fe₂O₃ content of 4% (mass fraction), a well-structured lithium tailings formed glass-ceramics is synthesized at 1 180 ℃, which exhibits an average pore size of 0.95 mm, a bulk density of 0.29 g/cm³, and a compressive strength of 3.19 MPa. Furthermore, increasing the Fe₂O₃ content promotes the transformation of the primary crystalline phase from azurite to fine-grained spinel, accompanied by a reduction in pore size. However, excessive Fe₂O₃ content (>4%) leads to an elevated sintering temperature and diminishes foaming ability.

Glass

Effect of B₂O₃ on Structure and Crystallization Behavior of Li₂O-ZnO-Al₂O₃-SiO₂ Glass-Ceramics

WEN Zhongyuan, LI Luyao, WANG Jing, HAN Jianjun

2025, 44(12):  4546-4556.  doi:10.16552/j.cnki.issn1001-1625.2025.0586

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Transparent glass-ceramics have found extensive applications in smart terminals and wearable devices due to their exceptional optical and mechanical properties, whose performance characteristics are intrinsically governed by the crystalline phase parameters, including species, concentration, dimensional features, and spatial distribution of nanocrystals within the glass matrix. Transparent Li₂O-ZnO-Al₂O₃-SiO₂ (LZAS) glass-ceramics were fabricated via a melt-heat treatment method, and the effect of B₂O₃ content on their structural evolution, crystallization behavior, and properties was systematically investigated. Results indicate that as the B₂O₃ content in the glass increases from 1% (mole fraction, same below) to 5%, the [BO₄] within the glass gradually transforms into [BO₃]. The proportion of [BO₃] stabilizes at approximately 49% when the B₂O₃ content ranges from 3% to 5%. Glasses containing 1% to 3% B₂O₃ tend to undergo surface crystallization after heat treatment at 760 ℃. In contrast, glasses with B₂O₃ content no less than 4% precipitate uniformly distributed spherical crystals within the bulk glass-ceramic matrix after crystallization at 780 ℃. Increasing the B₂O₃ content lowers the crystallization temperature required for bulk crystallization. The sample prepared from the glass containing 4% B₂O₃ and crystallized at 760 ℃ exhibits a transmittance of 65%, a Vickers hardness of (6.77±0.07) GPa, and a bending strength of (172.7±8.1) MPa.

Effect of Ru/Pd on Precipitation Phases and Morphologies of Platinum Group Metals from Simulated HLLW Glass

ZHU Qiaofeng, MENG Xiangda, FENG Jinyang, NIU Chenchen, LIU Yujie, ZHAO Qingbin, XU Kai

2025, 44(12):  4557-4566.  doi:10.16552/j.cnki.issn1001-1625.2025.0595

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The precipitation behaviour of platinum group metals in glass melts remains a key research focus within high-level liquid waste (HLLW) vitrification technology. The present study investigated the effects of varying mass ratio of RuO₂ and PdO (Ru/Pd), melting durations, and melting temperatures on the precipitation phases and morphologies of platinum group metals in glass melts. Test results from XRD and SEM-EDS indicate that samples with different Ru/Pd primarily form aggregates of granular RuO₂ and spherical Pd metal. A decrease in the Ru/Pd, or a prolongation of the melting duration, has been shown to increase the average diameter of Pd spheres. Furthermore, it is observed that the transformation of spherical to irregular Pd metal occurrs, resulting in a distinctive structure with Pd metal covered by RuO₂. It has been demonstrated that elevated melting temperatures significantly promote the reduction of PdO. RuO₂ and Pd metal are the predominant phases in glass melts at melting temperature of 1 000 ℃ and above.

Refractory Materials

Research Progress on Alkaline Melt Erosion Resistance of Refractory Materials

YANG Qinhao, HE Feng, TIAN Yingliang, ZHAO Zhiyong, GAO Manman, XIE Junlin

2025, 44(12):  4567-4580.  doi:10.16552/j.cnki.issn1001-1625.2025.0624

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With the development of new technologies in industries such as new energy, metallurgy, chemical industry, and waste salt treatment, the erosion of refractory materials used in high-temperature equipment by alkaline melt has become increasingly prominent. Consequently, extensive research has been conducted in this field. This paper reviews the research progress on the alkaline melt erosion resistance of refractory materials, with emphasis on analyzing the advantages and disadvantages of the static crucible method and dynamic methods in different erosion experiments. It discusses the erosion of refractory materials by alkaline melt generated in industrial processes such as new energy, metallurgy, chemical industry, and waste salt treatment. Furthermore, it reviews the alkaline melt erosion resistance behavior and mechanisms of MgO-based refractories, Al₂O₃-SiO₂-based refractories, Cr₂O₃-based refractories, and ZrO₂-based refractories. The aim is to provide a theoretical basis and technical reference for understanding the erosion behavior of alkaline melts, optimizing the design of refractory materials, and enhancing the service life of high-temperature equipment.

Functional Materials

Preparation and Properties of SiO₂ Aerogel Flexible Composites

PI Dengmiao, ZHAO Xiaoyan, SONG Lisiying, CHEN Jiaxuan, YANG Ziang, ZHANG Dingri, SONG Miao

2025, 44(12):  4581-4591.  doi:10.16552/j.cnki.issn1001-1625.2025.0550

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SiO₂ aerogel flexible composites have become a research hotspot in the aerogel industry due to their good flexible, processability, thermal insulation and other properties. However, SiO₂ aerogel flexible composites generally face a series of problems, such as high cost, high thermal conductivity, difficult uniform dispersion, poor stability and low solid content. In this study, SiO₂ aerogel was prepared by sol-gel method combined with atmospheric pressure drying process. SiO₂ aerogel was used as the core raw material, and SiO₂ aerogel coating was prepared by adjusting the solid content of SiO₂ aerogel powder and stirring dispersion process. Subsequently, SiO₂ aerogel coatings were compounded with spandex substrates by coating technology to prepare SiO₂ aerogel flexible composites. The effect of SiO₂ aerogel solid content on the structure and properties of the SiO₂ aerogel flexible composites was systematically investigated by microstructure characterization and performance testing. The results show that the apparent density of the self-made SiO₂ aerogel is 0.07 g/cm³, and the specific surface area is as high as 872 m²/g. When the SiO₂ aerogel solid content is 8% (mass fraction), the thermal conductivity of the SiO₂ aerogel flexible composite with the thickness of 1 mm is as low as 0.023 W/(m·K), and it can be insulated above 30 ℃ at 150 ℃. In addition, the minimum temperature difference between the material surface and the environment is only 1.1 ℃ after the copper foil is compounded with the SiO₂ aerogel flexible composite material with a SiO₂ aerogel solid content of 4% (mass fraction). This study provides an important reference for the application of high solid content SiO₂ aerogel flexible composites in the fields of thermal insulation, infrared stealth and so on.

Preparation and Performance of Mullite Fiber/SiO₂-ZrO₂-Y₂O₃ Aerogel Composite Thermal Insulation Felts

MA Chao, JIAN Sihao, HAN Minhang, WANG Kun, LI Yuheng, MIAO Yang

2025, 44(12):  4592-4603.  doi:10.16552/j.cnki.issn1001-1625.2025.0597

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The SiO₂ aerogel exhibits excellent thermal insulation performances, however, its structure tends to sinter and collapse at high temperatures, and it has relatively high brittleness, which limit its widespread application in high-temperature and complex environments. This study employed the sol-gel method and supercritical drying technology, using tetraethyl orthosilicate as the silicon source, to prepare mullite fiber/SiO₂-ZrO₂-Y₂O₃ aerogel composite thermal insulation felts (MF/SZYAs). A systematic investigation was conducted on the microstructure, thermal insulation performance, and high-temperature thermal stability of MF/SZYAs. The results indicate that the prepared MF/SZYAs possess a well-developed nanoscale three-dimensional network pore structure, with zirconium and yttrium elements uniformly distributed within the aerogel matrix. At room temperature, the density of MF/SZYAs is 0.134 5 g·cm^-3, with a compressive strength of 2.26 kPa at 10% strain, a specific surface area of 515.7 m²·g^-1 and a thermal conductivity of 0.035 1 W·m^-1·K^-1. After heat treatment at 1 000 ℃, MF/SZYAs exhibit excellent thermal stability, with a thermal conductivity of 0.045 4 W·m^-1·K^-1 and a specific surface area of 183.1 m²·g^-1. Following heat treatment at 1 200 ℃, although the macroscopic volume of MF/SZYAs remains largely unchanged, significant sintering occurs within the internal three-dimensional nanostructure, resulting in a notable decrease in specific surface area (14.3 m²·g^-1) and an increase in thermal conductivity (0.047 3 W·m^-1·K^-1). Good thermal stability is primarily attributed to the enhanced structural stability and thermal radiation scattering ability of SiO₂ aerogels due to the co-doping of zirconium and yttrium. The research results provide important theoretical support for the development of efficient, lightweight, and thermally stable thermal insulation materials, and the prepared composite thermal insulation materials have wide application prospects in the industrial field.

Fabrication Through Ion Crosslinking Method and Microwave Absorption Properties of Fe-Ni-P-S/Carbon Aerogel

ZHOU Weihong, LI Yuhuan, CUI Zijian, JI Yongfeng

2025, 44(12):  4604-4612.  doi:10.16552/j.cnki.issn1001-1625.2025.0621

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Porous carbon materials have great application potential in the field of electromagnetic wave absorption. In this paper, a gel with three-dimensional network structure was constructed by coordination crosslinking of metal cations with the polar groups of nanocellulose, and then Fe-Ni-P-S/carbon aerogel (Fe-Ni-P-S/CA) composites were prepared through the process of freeze-drying and calcination. The structure and composition of Fe-Ni-P-S/CA composites were characterized by FTIR, XRD, Raman, SEM and EDS. The results show that in addition to Fe-Ni alloy phase, Fe-Ni-P-S/CA composites also contain compound phases formed by Fe, Ni, and P, S. Carbon aerogel exhibits loose and porous structures. Fe-Ni-P-S/CA composites show excellent microwave absorption properties. The reflection loss reaches a minimum value of -59.63 dB at the simulated matching thickness of 2.0 mm, and the maximum effective absorption bandwidth is up to 4.6 GHz at the simulated matching thickness of 1.9 mm. The porous structure of the carbon matrix enhances the impedance matching characteristics and multiple reflection loss. Fe-Ni alloy and FeP₂ micro-nano particles lead to interfacial polarization loss. The ion crosslinking method used in this paper has simple process, which provides new ideas for the development of biomass-derived carbon-based microwave absorption materials.

Luminescence Properties of Sm³⁺ Activated β-CaTa₂O₆ Orange-Emitting Phosphor and Its Anti-Thermal Quenching Behavior

GUO Yu, LI Fangzheng, JIANG Quan, RUAN Jian, TIAN Chen, HAN Jianjun, LIU Chao

2025, 44(12):  4613-4622.  doi:10.16552/j.cnki.issn1001-1625.2025.0453

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Owing to their unique optical properties, long-wavelength-emitting rare-earth-activated phosphors have important applications in optoelectronic fields such as white light-emitting diodes (LEDs). In this study, Sm³⁺-activated β-CaTa₂O₆ orange-emitting phosphors (CTO∶xSm, x=0.01~0.06) are successfully synthesized by high-temperature solid-state reaction method. Under excitation at 405 nm, the most intense emission peak is located at 606 nm originating from the ⁴G_5/2→⁶H_7/2 transition of Sm³⁺. The phase structure and luminescent properties were systematically characterized by XRD, Rietveld refinement, SEM, fluorescence spectra and thermoluminescence spectroscopy. The obtained phosphors are found to be single phase. Sm³⁺ ions are supposed to occupy Ca²⁺ sites, which leads a slight lattice contraction. The optimal doping concentration of Sm³⁺ is 2% (mole fraction) and the concentration quenching mechanism should be attributed to dipole-dipole interaction. An anomalous anti-thermal quenching behavior is also observed in CTO∶0.02Sm, which should be associated with defects induced by charge imbalance. The emission intensity initially increases rapidly and then slightly decreases with temperature rising. It reaches 239% of the room-temperature intensity at 548 K. The CIE 1931 chromaticity coordinates are (0.586 0, 0.411 2). It also shows a high color purity of 99.34% and a photoluminescence quantum yield (PLQY) of 41.83%. It should be promising for white LEDs with high color rendering index.

Green Preparation of Self-Forming Type A Zeolite Foam from Activated Rectorite

QIU Xiumei, LIU Yi, LIU Yadong, CAI Hao, LIU Yedongyang, LIANG Yaqi

2025, 44(12):  4623-4632.  doi:10.16552/j.cnki.issn1001-1625.2025.0864

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In order to break through the limitations of traditional zeolites, which rely on chemical raw materials and additional binders for shaping, this study adopted thermal activation to prepare activated rectorite and explored the feasibility of synthesizing self-forming type A zeolite from it via a quasi-solid-state method. The effect of calcination at 600~1 000 ℃ on the physicochemical properties of rectorite ore was investigated. The results of XRD, FTIR, and SEM show that the framework structure of rectorite is completely destroyed after calcination at 1 000 ℃, SiO₄ tetrahedral units are distorted, while AlO₆ octahedral units decompose. However, the chemical composition of rectorite remains basically stable. Synthesis experiments demonstrate that using rectorite activated at 1 000 ℃ as the raw material, under the induction of type 4A zeolite seed crystals, high-purity self-forming type A zeolite foam could be directly formed under the following conditions: Na₂O/Al₂O₃ molar ratio of 1.00, H₂O/Na₂O molar ratio of 14.50, and crystallization at 70 ℃ for 24 h. The results of SEM, XRD, and other techniques reveal that the self-forming type A zeolite exhibits a relatively regular cubic lamorphology, with dense stacking between particles. A self-forming type A zeolite foam with a compressive strength of 1.45 MPa is formed without the need for additional binders. This method provides a new approach for the resource utilization of rectorite and the green, low-cost preparation of bodying zeolites.

Road Materials

Engineering Characteristics and Environmental Impact Assessment of Modified Red Mud in Subgrade

LUO Tingyi, LI Ruijie, WEI Caichao, WANG Chaoyi, LUO Liufen

2025, 44(12):  4633-4645.  doi:10.16552/j.cnki.issn1001-1625.2025.0617

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Red mud, a solid waste from alumina industry, contains alkaline oxides with potential activity, which can be used as building materials after modification. In this paper, lime, slag, desulfurization gypsum and other materials were introduced to modify red mud, and its application in highway subgrade filling was studied. The single-doped and double-doped test schemes were designed. The maximum dry density and optimum moisture content of red mud under different mix ratios were determined by conducting compaction test. According to California Bearing Ratio (CBR), rebound modulus and unconfined compressive strength, the optimal mix ratio was selected, and its environmental impact was evaluated. The results show that the incorporation of modified materials improves the mechanical properties of pure red mud. When the total mass fraction of slag and lime is 10% (double-doped with a mass ratio of 1∶1), the CBR strength, rebound modulus and unconfined compressive strength of the modified red mud subgrade material are the most obvious, and the maximum values are 306.22%, 123.58 MPa and 3.02 MPa, respectively. Compared to single-doped modified material at the same content, the CBR strength of the double-doped group increases by 129%, the rebound modulus increases by 28%, and the unconfined compressive strength increases by 148%. The release rates of the characteristic pollutants Cd, V, Se, As and fluoride in the long-term migration process of the modified red mud subgrade material tend to be stable and the concentration values are lower than class Ⅰ standard limit of groundwater.

Effect Evaluation of Aggregate Composition on Road Performance of Polyether Polyurethane Mixture

XIE Zhitian, WANG Mingyu, SUN Chuanxia, SHI Liang, HUO Chunhui

2025, 44(12):  4646-4658.  doi:10.16552/j.cnki.issn1001-1625.2025.0539

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To investigate the effect of aggregate composition on the performance of polyether polyurethane mixture (PPUM), this study employed the PC-13 gradation and designed three aggregate composition schemes of PPUM (full limestone (PC-1), limestone+basalt (PC-2) and full basalt (PC-3)). The effects of aggregate composition and three environmental factors of thermal-oxidative aging, ultraviolet radiation and water on the road performance of PPUM were evaluated, respectively. The performance evolution law of PPUM was revealed and the prediction model of performance impacts was established. The results show that the road performance of PC-1 is the worst among the three aggregate compositions, and the road performance of PC-3 is the best. The road performance of PC-2 is lower than that of PC-3, but the decrease is not more than 10%. The performance decay law of PPUM with three aggregate compositions is similar, which shows that ultraviolet radiation and thermal-oxidative aging have no effect on the high temperature performance of PPUM, but have a significant effect on indirect tensile strength, low temperature performance and water stability performance. Repeated freeze-thaw cycles have a significant effect on the water stability performance of PPUM.The established prediction model of environmental factors on performance has high fitting accuracy.