Table of Content

Volume 43 Issue 10
15 October 2024

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Cement and Concrete

Advances in Properties of Plant Fiber Reinforced Concrete

LIU Maojun, XU Guoping

2024, 43(10):  3499-3509. 

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Plant fibers have the characteristics of light weight, high specific strength and high elongation at break, which can improve the shortcomings of concrete such as easy cracking, low tensile strength and brittle damage. At the same time, plant fibers can improve the thermal insulation properties and durability of concrete. First of all, the chemical composition and mechanical characteristics of various commonly used plant fibers were analyzed, and the modification methods of plant fibers were also discussed. Then, the researches of domestic and foreign scholars on mechanical properties, hydration characteristics, thermal insulation properties and other properties of plant fiber reinforced concrete were analyzed and summarized in detail. And the following conclusions are drawn: when using plant fibers to enhance the strength of concrete, the long fiber lay-flat method has the best effect on the enhancement of tensile strength, while the short fiber in-mixing method has a wider range of applications, and at the same time, a variety of factors, such as fiber length, fiber content, and water-cement ratio, affect the mechanical properties of concrete; plant fibers can retard the release of heat of hydration by changing the hydration characteristics of cement, thus enhancing the crack resistance of mass concrete; plant fibers can improve the thermal insulation properties and durability of concrete, and reduce the cracking of concrete through the endotrophic effect of plant fibers on concrete.

Synergistic Influence Mechanism of Fluorine, Phosphate and Heavy Metal Ions Co-Doping on Formation and Hydration of Tricalcium Silicate

DU Huan, DA Yongqi, HE Tingshu, HAO Jianheng

2024, 43(10):  3510-3523. 

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Fluorinated sludge, as the main byproduct of refined production in the semiconductor industry, is a hazardous solid waste. In the process of co-treating fluorine-containing sludge in cement kilns, the fluorine, phosphate, and various heavy metal ions contained in the fluorinated sludge will inevitably be introduced into the cement raw material at the same time. These ions will significantly affect and change the calcination process and properties of cement raw material minerals. However, there are few studies on the impact of their coexistence on the properties of cement clinker. Therefore, this paper systematically studied the synergistic influence mechanism of fluorine, phosphate, and heavy metal ions co-doping on the calcination process, microstructure, and hydration characteristics of tricalcium silicate (C₃S). The results show that compared with the single doping of phosphorus, the co-doping of phosphate and heavy metal ions is not conducive to the firing of C₃S, while the co-doping of fluorine, phosphate, and heavy metal ions has a significant synergistic promoting effect on the firing of C₃S, while significantly improving the symmetry of C₃S crystal structure, resulting in more defects of different types on the surface of C₃S minerals. Compared with the single doping ofphosphorus, the co-doping of phosphate and heavy metal ions is beneficial for improving the initial and later hydration rates of C₃S, reducing the aspect ratio of rod-shaped hydrated calcium silicate (C-S-H). The effect of co-doping of fluorine, phosphate, and heavy metal ions on the hydration performance of C₃S depends on the doping ratio of each ion. However, as the doping amount of each ion increases, the acceleration period of C₃S hydration will be continuously delayed, and the co-doping of the three ions will promote the increase of the aspect ratio of rod-shaped C-S-H.

Interfacial Bonding Properties of Graphene/Graphene Oxide and Calcium Silicate Hydrate

YAO Jie, YANG Lan, WU Puwei

2024, 43(10):  3524-3533. 

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The debonding behavior of graphene/graphene oxide on calcium silicate hydrate substrate directly affects the performance of gelling composites, however it is difficult to achieve the debonding effect in traditional experiments. In order to clarify the debonding characteristics of graphene/graphene oxide, the debonding behavior of graphene/graphene oxide on calcium silicate hydrate substrate at nanoscale by molecular dynamics method was studied. The results show that the bonding properties of graphene/graphene oxide decrease with the increase of temperature, compared with graphene, the change of temperature has a greater effect on the bonding properties of graphene oxide. Among graphene oxide, epoxy-based graphene oxide is least affected by the change of temperature. The main factors affecting the bonding properties are the van der Waals forces and Coulomb interactions between graphene/graphene oxide and calcium silicate hydrate. High concentration and functional groups at the edge can significantly enhance bonding properties, and the effect of different functional groups on enhancing bonding properties is carboxyl group, hydroxyl group and epoxy group.

Effect of D-Sodium Erythorbate on Properties of Magnesium Oxysulfate Cement

MA Yuan, XU Feng, MA Jianyan, YU Liyi, ZHOU Yeqi, DING Xiangqun, ZHANG Shu, WANG Ningwei

2024, 43(10):  3534-3540. 

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The effect of D-sodium erythorbate on the setting time, conductivity, compressive strength, and water resistance of magnesium oxysulfate cement was investigated. The phase composition and microstructure of hydration products of magnesium oxysulfate cement were analyzed using X-ray diffraction, synchronous thermal analysis, and scanning electron microscopy. The results show that the addition of chemical additive D-sodium erythorbate significantly prolongs the setting time of magnesium oxysulfate cement. Additionally, the formation of a substantial amount of 5Mg(OH)₂· MgSO₄·7H₂O(5·1·7) crystalline phase greatly improves the compressive strength and water resistance of magnesium oxysulfate cement.

Effect of Modified Alcohol Amine on Properties of Cement and Its Mechanism

LIU Chunduo, LIU Kai, NING Chaoyang, MU Song, YANG Jing, CAI Jingshun

2024, 43(10):  3541-3551. 

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In view of the unclear action mechanism of modified alcohol amine in commercial reinforcers, the effects of modified alcohol amine (CS_M, CS_N and CS_O) on setting time and strength of paste were investigated, and the effects of modified alcohol amine on cement hydration process, hydration products and microstructure of paste were investigated by means of hydration heat, cement quantitative XRD and microstructure SEM test, and compared with triisopropanolamine (TIPA). The results show that TIPA, modified alcohol amine all show retarding properties, and CS_O has the strongest retarding property. In terms of strength, TIPA improves the strength development of cement paste during the test age, and CS_M improves the strength development of cement paste for 7~28 d, and the improvement effect is better than that of TIPA, CS_N and CS_O have negative effects on strength. In terms of mechanism, the addition of CS_M increases the hydration degree of cement mineral phase, optimizes the hydration rate, improves the microstructure of hydration products, promotes the interlacing of C-S-H, Ca(OH)₂ and ettringite, and improves the compactness of paste. TIPA promotes the hydration of C₄AF. CS_N and CS_O promote the hydration of C₃S and C₄AF, but the rapid hydration of mineral phase and compact microstructure can not achieve coordination. In terms of modification measures, compared with amino and hydroxyl modification, TIPA molecular weight modification is more helpful to improve cement hydration process, product distribution structure and promote the development of cement paste strength.

Effect of Sulphoaluminate Cement on Early Hydration and Mechanical Properties of Portland Cement

ZHANG Yan, HUANG Yesheng, LIU Jialong, CAO Haoyu, LI Wei, LIU Ying, XIAO Qunan, ZHANG Xiaoying, XIE Fengwei

2024, 43(10):  3552-3560. 

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The prefabricated construction has rapidly transformed the building industry, and achieveing the swift demolding of component is fundamental for the rapid development of prefabricated industry. The effects of sulphoaluminate cement (CSA) at low replacement rate (from 2.5% to 7.5% of cement mass) on the early hydration and mechanical properties of Portland cement were studied. Setting time, compressive strength, hydration heat, XRD, TG, and SEM were used to expose to the behind mechanism, providing solutions for the rapid demolding of prefabricated component. The result show that the incorporation of CSA can shorten the setting time of Portland cement, enhance early hydration, and improve early mechanical properties. With the increase of the CSA mass fraction from 2.5% to 7.5%, the initial setting time reduces by 30%, 43% and 49% respectively, and the final setting time by 24%, 40% and 46%, respectively. 5% mass fraction of CSA increases the 12 h compressive strength from 5.2 MPa to 12.8 MPa, an increase of 169%. Additionally, CSA also improves the later-stage mechanical properties of the system.

Permeability of Peat Soil Solidified by Composite Cement Solidification Agent

CAO Jing, ZHANG Xingwen, LEI Shuyu, LI Yuhong, CHENG Yun

2024, 43(10):  3561-3571. 

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In response to the challenges of poor engineering properties and the high difficulty in improving peat soil, a composite cement solidification agent (CCS) comprising ultra-fine cement (UFC) and ordinary Portland cement (OPC) was proposed for the solidification of simulated peat soil. The influence of UFC on the permeability of cement-soil samples was investigated through osmotic pressure tests and X-ray diffraction (XRD) experiments. Osmotic pressure tests results indicate that, under constant CCS dosage, the permeability coefficient k of specimens decreases with increasing UFC mass fraction, with a significant attenuation of the decreasing trend observed when the UFC mass fraction exceeds 12%. For CCS with a UFC mass fraction of 12%, k decreases with increasing CCS dosage, and the declining trend is notably attenuated when the dosage exceeds 25%. XRD results indicate that the diffraction peak intensity of calcium silicate hydrate (C-S-H) in the samples increases with both the increase in the UFC mass fraction and the curing time. Compared to OPC, CCS achieves superior solidification efficiency with a reduced cement dosage, facilitating the attainment of carbon reduction objectives.

Experimental Study on Basic Mechanical Properties of Polypropylene Fiber-Reinforced Ceramsite Concrete

GU Fei, LI Congqi, YANG Ying, LI Huilong, JIN Ziran, WANG Xin, LIU Hushan

2024, 43(10):  3572-3584. 

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In order to improve the strength and brittleness of ceramsite concrete, polypropylene fiber was added to ceramsite concrete in this study. A total of 180 polypropylene fiber-reinforced ceramsite concrete specimens were prepared, and cube compressive test, splitting tensile test, axial compressive test and elastic modulus test were carried out. The results show that polypropylene fiber can effectively improve the splitting tensile strength and tension-compression ratio of ceramsite concrete, and has little effect on compressive strength and elastic modulus. Based on the experimental results, the conversion relationship model between splitting tensile strength and cube compressive strength, axial compressive strength and cube compressive strength, and the numerical model of elastic modulus of polypropylene fiber-reinforced ceramsite concrete were proposed.

Effects of Fly Ash and Steel Fiber on Abrasion Resistance of Ultra-High Performance Concrete

DING Dawei, GUO Zihan, ZHANG Wei, ZHANG Xiuxin, MA Yitong, WANG Xinpeng, HOU Dongshuai

2024, 43(10):  3585-3594. 

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In order to investigate the effects of fly ash and steel fiber on the abrasion resistance of ultra-high performance concrete (UHPC), this paper performed macroscopic mechanical test, underwater abrasion resistance test and microscopic characterization such as SEM and MIP to investigate the effects of fly ash and steel fiber on the workability, mechanical properties, microstructure, and abrasion resistance of UHPC. The results show that the replacement of cement by fly ash delays the emergence of hydration peak by about 3 h, and the cumulative heat flow at 3 d is reduced by 18%, significantly improving the workability of UHPC. The incorporation of fly ash reduces the mechanical properties of UHPC in the early stage and has no effect on the mechanical properties in the later stage. The incorporation of steel fiber improves the flexural strength and compressive strength of UHPC. The flexural strength and compressive strength are increased by 82% and 47% respectively due to the composite mixing of steel fiber and fly ash under steam curing. The addition of fly ash has little effect on the abrasion resistance of UHPC, while the addition of steel fiber improves the abrasion resistance of UHPC, and the composite mixing of steel fiber and fly ash increases the abrasion resistance of UHPC by 58%. The compressive strength and abrasion resistance strength of UHPC show a significant positive correlation. The incorporation of fly ash reduces the most available pore size, porosity and capillary pore content, making the internal structure of matrix more uniform and denser.

Corrosion of Steel Reinforcement in Buried Alkali-Activated Slag Concrete under Stray Current and Complex Ion Action

LI Xiangxiang, JIN Zuquan, PANG Bo

2024, 43(10):  3595-3606. 

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The corrosion of steel reinforcement in underground engineering concrete, such as that found in coastal subways, is susceptible to occurring under the combined influences of stray current and corrosion ions. The corrosion behavior of steel reinforcement in different environments was studied. The real-time strain monitoring, electrochemical impedance spectroscopy (EIS), and microscopic analysis were employed for both ordinary Portland cement (OPC) concrete and alkali-activated slag (AAS) concrete. The results show that the steel reinforcement in concrete undergoes pitting corrosion. The chemical composition of corrosion products formed in the steel reinforcement appears to be unaffected by the type of concrete or the presence of corrosion ions. Furthermore, the corrosion rate observed in AAS concrete is found to be lower than that in OPC. Additionally, the time of deactivation of steel reinforcement and concrete rust expansion cracking is relatively logging behind. As the concentration of sulfate ions in saline soil increases, the rust cracking time and rust cracking force of steel reinforcement concrete increase first and then decrease. This suggests that sulfate ions have a mitigating effect on the corrosion rate of steel reinforcement induced by chloride salts.

Formation and Failure Law of Rebar Passivation Film in Liquid Phase Environment of Alkali-Activated Slag

WAN Xiaomei, WANG Boshi, SUN Zhongtao, ZHANG Dongfang

2024, 43(10):  3607-3614. 

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To explore formation and failure mechanism of rebar passivation film in the liquid-phase environment of alkali-activated slag (AAS) system, AAS cementitious material systems with different mixing designs were prepared. The time-dependent evolution of the pH value of AAS real pore solution was studied in various factors such as different types of activator, alkali equivalent, water-glass modulus, fly ash addition, and curing time. In addition, the generation time, composition, thickness, and critical chloride threshold of rebar passivation film in simulated pore solution were monitored and analyzed over time. The results show that the pH value of AAS real pore solution decreases with the increase of curing time, with pH values of all samples remaining above 12.8 at 28 d. The increase in pH value in the simulated pore solution reduces the formation time of rebar passivation film, increases its thickness, and enhances its resistance to chloride ion erosion. The characteristic of AAS real pore solution having a higher pH value can provide a more favorable liquid phase environment for the stable existence of rebar passivation film, thereby improving the long-term performance of reinforced concrete structures.

Effects of Anti-Corrosion Coating/Treating Ages on Performance Evolution of Marine Cast-in-Place Concrete

JIANG Jinyong, ZHU Haiwei, QIAN Xin, YANG Haicheng, FAN Congjun

2024, 43(10):  3615-3622. 

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This article was based on indoor simulated marine environment erosion tests using concrete, by analyzing the compressive strength, coating bonding strength and chloride ion diffusion behavior of marine cast-in-place concrete after erosion, and the effects of anti-corrosion coating/treating ages on the mechanical properties and durability evolution of marine cast-in-place concrete were studied. The results show that compared with concrete without anti-corrosion coating/treating, anti-corrosion coating/treating concrete using silane and polyurethane coating shows a decrease in compressive strength f_c after erosion in marine tidal areas, and concrete f_c gradually decreases with the increase of curing age t_c. Anti-corrosion coating/treating can effectively improve the long-term chloride ion erosion resistance of marine cast-in-place concrete, and with the increase of curing age t_c, the effects of anti-corrosion coating/treating on reducing the surface chloride ion content C_s and apparent chloride ion diffusion coefficient D_a of concrete becomes more significant. Taking into account the development of mechanical properties of cast-in-place concrete in the marine tidal zone environment and the effectiveness of anti-corrosion coating/treating measures, it is recommended to use silane and polyurethane coatings for coating with a curing age of not less than 5 and 10 d, respectively.

Flexural Performance of PP-ECC Bridge Pier under Simulated Earthquake

JIA Yi, LIU Pengzeng, LIU Qiqian, WANG Zihao, SONG Haobo

2024, 43(10):  3623-3633. 

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In order to study the difference of bearing capacity between polypropylene fiber reinforced engineered cementitious composite (PP-ECC) bridge pier and ordinary concrete bridge pier under compressive-bending load, the flexural performance of six PP-ECC bridge piers and two ordinary concrete bridge piers were studied by quasi-static test. Combined with the failure process of PP-ECC bridge pier, the characteristic points of compressive-bending failure of PP-ECC bridge pier were determined. Then, based on the simplified constitutive model of PP-ECC material, the theoretical cracking, yield and ultimate load formulas of PP-ECC bridge pier were derived. The characteristic parameters of the simplified PP-ECC constitutive model were determined by uniaxial tensile and uniaxial compression tests of PP-ECC materials. The calculation results were verified by the experimental results, and the differences of flexural bearing capacity and maximum deformation of piers under different axial compression ratios and PP-ECC zone heights were compared. The results show that after PP-ECC bridge pier is cracked, PP-ECC in the tensile zone still work, and cooperates with the tensile steel bar to participate in the section force. When PP-ECC bridge pier reaches the ultimate load, the crack develops steadily, and there is no large area of concrete spalling in the protective layer of ordinary concrete pier. The maximum deformation of PP-ECC bridge piers under ultimate load are larger than that of ordinary concrete piers, and the increase of axial compression ratio will reduce the deformation capacity of piers. Increasing the height of PP-ECC zone at a higher axial compression ratio, the flexural capacity of the pier increases by 8.8%. When using the simplified constitutive model to calculate the flexural bearing capacity of PP-ECC bridge pier feature points, the calculation accuracy reaches 0.86~1.13, and the variance analysis value is small, which has good calculation accuracy.

Interpretable Prediction of Compressive Strength of Ultra-High Performance Concrete Based on AutoML-SHAP

LI Shuo, AILIFEILA Aierken, LUO Wenbo, CHEN Jinjie

2024, 43(10):  3634-3644. 

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The correlations between compressive strength of UHPC and its mixture composition exhibit pronounced nonlinearity, presenting a challenge for analysis through conventional statistical approaches. In this study, an automatic machine learning (AutoML) technology was proposed to predict compressive strength of UHPC, and shapley additiveex planations (SHAP) was introduced to explain the AutoML model. The integration of AutoML and SHAP offered synergistic benefits, facilitating the development of a precise, efficient, and comprehensively interpretable model. Results demonstrate that AutoML model is automatically built with better accuracy and robustness than the base model. SHAP provides a global explanation, a single sample explanation, and a feature dependence explanation of characterization factors, which explains mechanism of the effect of each characterization factor on compressive strength. SHAP contributes to the understanding of mechanism of UHPC compressive strength development and the importance of characteristic factors, and can provide assistance in the design and application of UHPC.

Multi-Objective Intelligent Optimization Design Method Based on NSGA-II High Performance Concrete Mix Proportion

HU Yichan, WENG Yiling, CHI Hao, HU Lei, PENG Hao, LIANG Jian, ZHOU Fujian, HUANG Wensheng, XIE Weiwei

2024, 43(10):  3645-3654. 

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In order to solve the problems of limited design parameters, over-reliance on manual adjustment and failure to make full use of the existing test data in the traditional proportion design, a novel intelligent optimization strategy for high performance concrete (HPC) was proposed, which integrates artificial intelligence algorithms and meta-heuristic search technology, and can realize the proportion design under the consideration of the multi-objective demand of HPC. Firstly, a database with a large amount of HPC proportion data and performance test information was constructed. Secondly, three machine learning algorithms, XGBoost, MLP and RF algorithm, were used to establish the nonlinear mapping relationship between compressive strength of concrete and the amount of material used, and the model with the best performance was selected as the strength objective function and constraints in the multi-objective optimization intelligent. Then, the Pareto optimal predicate was solved by establishing the mathematical model with the objectives of compressive strength, economy, and environmental protection, and the Pareto optimal predicate was solved by using the NSGA-II algorithm. Lastly, the unique optimal solution was obtained by combining with the ideal-point method. The proposed method was validated by practical engineering examples, and the results show that the proposed multi-objective intelligent optimization design method of high-performance concrete proportion takes into full consideration of interactions between variables, greatly reduces the number of tests, significantly improves the efficiency of the proportion design, and can provide a reference for the multi-objective intelligent proportion optimization design of HPC.

Solid Waste and Eco-Materials

Research and Application Progress of Iron Tailings Sand

HUANG Wei, XUE Kui, ZHANG Zilong, CAO Yonggang, WANG Jialiang, QIU Wenhao, CHEN Dongsheng

2024, 43(10):  3655-3665. 

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With the rapid development of China's mineral industry, the emission of iron tailings sand has increased sharply. At present, the negative storage and landfill are still the main treatment methods, which does not only occupy a large amount of land resources, but also cause serious environmental pollution. Therefore, large-scale consumption of iron tailings sand is imminent. Iron tailings sand is a kind of waste discharged after the ‘useful part' of iron ore is selected by grinding, flotation or magnetic separation under a certain condition. Compared with natural fine aggregate, the particle is finer, angular and more solid, which could be widely used in various practical projects. Among them, the regional differences of iron tailings, raw ore composition, grade, particle size and mining beneficiation refining process have a greater impact on the physical and chemical properties. As an inert material, different activation methods could be conducted to improve the activity of iron tailings sand, whereas, the composite activation is the most effective technology. In this paper, the utilization of building materials of iron tailings sand at home and abroad and its application in other fields are reviewed. The influence of concrete prepared by iron tailings sand on mechanical properties and durability is summarized. The key properties of the application in road functional materials are discussed. The application status of iron tailings sand-based bricks is sorted out. The feasibility of using it to prepare geopolymer is evaluated. Its advantages in the preparation of mesoporous molecular sieves and the improvement of expansive soil are discussed.

Experimental Study on Mix Proportion of Polyvinyl Alcohol Fiber Reinforced Desert Sand Concrete

ZHOU Lina, JI Funa, LI Xuezhi, PAN Wengui, MA Cailong

2024, 43(10):  3666-3676. 

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In order to give full play to the particle filling advantage of desert sand and improve the mechanical properties of desert sand concrete, this paper carried out an experimental study on the mix proportion design method of polyvinyl alcohol fiber reinforced desert sand concrete based on Dinger-Funk close-packing theory. Firstly, applying the Dinger-Funk close-packing theory, the optimized sand rate is 42%, the optimized desert sand mass replacement ratio is 10%, 20% and 30%, the concrete aggregate particle gradation is improved, the fineness modulus of mixed fine aggregate is reduced from 3.27 to 2.92, 2.81 and 2.71, and the effective porosity is reduced from 2.50% to 1.65%, 1.45% and 1.51%, respectively. Secondly, the orthogonal test method was used to study the effects of water-cement ratio, desert sand mass replacement ratio, and the volume dosage of polyvinyl alcohol fiber on the workability, compressive strength, splitting tensile strength and flexural strength of concrete. The results show that, with the increase of desert sand mass replacement ratio and fiber dosage, the workability of concrete firstly increase and then decrease, and the compressive strength, splitting tensile strength and flexural strength show the trend of firstly increasing and then decreasing. Considering the test results of the workability and mechanical properties, the optimal mix proportion of C30 polyvinyl alcohol fiber reinforced desert sand concrete is determined to be 0.45 water-cement ratio, 20% of desert sand mass replacement ratio, and 0.10% of polyvinyl alcohol fiber volume dosage.

Optimal Design and Experimental Study on Limestone Calcined Clay Composite Cementitious Material System Based on Response Surface Method

ZHAI Chen, ZHANG Qingnian, HUANG Jianfeng, QIU Shuheng, CHEN Xiaopeng, TONG Zhangfa

2024, 43(10):  3677-3685. 

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To explore the optimal ratio of limestone powder and calcined clay in the limestone calcined clay composite cementitious material system, the response surface method was adopted to optimize. The prediction model was established by taking ordinary Portland cement, calcined clay and limestone powder as variable factors, and 28 d compressive strength and 28 d flexural strength of cement mortar as response variable. Mechanical properties were tested, and the regression model between the proportion of mineral admixture compounding and the mechanical properties was established. At the conditions of mineral admixture proportion of 15%, 30% and 45% (mass fraction, the same below), the regression model was used to optimize the mixing ratio of limestone powder and calcined clay in the limestone calcined clay composite cementitious material system. The optimization results are as follows: calcined clay accounts for 15%, without limestone powder. Calcined clay accounts for 25%, and limestone powder accounts for 5%. Calcined clay accounts for 30.5%, and limestone powder accounts for 14.5%. The predicted values of 28 d compressive strength of system are 63.26, 58.57 and 48.10 MPa, respectively, while the measured values are 63.74, 57.21 and 47.02 MPa, respectively. The absolute relative errors between the predicted and measured values are less than 5%. It provides a new solution idea and test basis for the optimal proportioning problem of limestone calcined clay composite cementitious material system.

Deterioration Mechanism of Coal Gangue Shotcrete under Dry-Wet Cycles of Sulfate

LIU Chao, CAI Jianyun, ZHU Chao, YAO Yizhou

2024, 43(10):  3686-3693. 

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In order to promote the large-scale utilization of coal gangue in coal mine areas under high sulfate environment, this article prepared shotcrete with different coal gangue substitution rates, and studied the influence law of coal gangue on the sulfate attack resistance of shotcrete under the action of dry-wet cycles. The appearance, mass loss rate, relative dynamic elastic modulus, relative compressive strength, sulfate ion distribution evolution and micromorphology changes before and after erosion were studied, and the influence mechanism of coal gangue on the sulfate attack resistance of shotcrete was obtained. The results show that under the action of sulfate dry-wet cycles, the deterioration process of coal gangue shotcrete (CGS) is divided into three stages: strengthening stage, initial damage and macroscopic damage. The deterioration degree of CGS is synergistically affected by the number of dry-wet cycles and the substitution rate of coal gangue. The sulfate resistance of CGS increases at a substitution rate of 25% (mass fraction). When the substitution rate exceeds 25%, the sulfate attack resistance of CGS decreases with the increase of substitution rate. The research results provide important theoretical support for the application of CGS structures in mines.

Mechanical Properties and Microstructure Analysis of Metakaolin-Phosphoric Acid Based Geopolymer

DUAN Liwei, LUO Anbang, CHEN Yinghao, WANG Dehui, LUO Zhengdong

2024, 43(10):  3694-6703. 

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In order to clarify the optimal liquid-solid ratio (L/S) values for the activation of metakaolin at different concentrations of phosphoric acid solution, five sets of phosphoric acid solution of 4, 5, 6, 7 and 8 mol·L^-1 were set up, and four L/S values of 0.6, 0.7, 0.8 and 0.9 were used for preparation of metakaolin-phosphoric acid based geopolymer (MPAG). The 7 and 28 d compressive and flexural strengths of MPAG were used as the evaluation indexes to investigate the effects of above preset variables on its mechanical properties. The compressive strength of samples corresponding to the optimal L/S value concentration of each group after sulfate erosion were further investigated. Finally, the phase composition and microscopic morphology of MPAG were characterized and analyzed. The results show that MPAG is mainly composed of an amorphous aluminum phosphate phase. Greater compressive strength can be obtained by using L/S value of 0.6 when the concentration of phosphoric acid solution is 4~6 mol·L^-1, and when the concentration increase to 7~8 mol·L^-1, the recommended of L/S value is 0.7. MPAG exhibits good sulfate resistance, with a compressive strength retention rate of 84% to 93% after 28 d immersion. The samples prepared with 6 mol·L^-1 phosphoric acid under any L/S value achieved the maximum flexural strength for that L/S value. The 28 d maximum flexural strength is 6.80 MPa when L/S value is 0.6. The results of this study can provide references for the preparation and application of MPAG.

Preparation and Properties of Sulfur Tailings-Based Geopolymer Activated by Alkaline Hydrothermal Method

WANG Wenyao, LUO Qi, LU Liulei, LAI Jin, HUANG Wenhao, ZHUANG Rongchuan, WANG Junfeng, MA Jun

2024, 43(10):  3704-3714. 

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To solve the problem of high energy consumption in tailings pretreatment methods and explore a low energy consumption tailings activation method, alkaline hydrothermal activation pretreatment was carried out on part of sulfur tailings to enhance their activity and improve the mechanical properties of sulfur tailings-based geopolymers. The influences of activation temperature and activation time on alkaline hydrothermal activation effect have been studied. X-ray diffraction technology, Fourier transform infrared spectroscopy analysis, thermogravimetric analysis, nuclear magnetic resonance imaging analysis, and scanning electron microscopy test were used to characterize the performance of activated sulfur tailings and sulfur tailings-based geopolymers. The results show that when the sulfur tailings are activated at 200 ℃ for 2.0 h, the prepared geopolymer obtains the highest 3 and 28 d compressive strength, which are 15.5 and 22.1 MPa, respectively. Alkaline hydrothermal activation can effectively destroy the crystalline phase in sulfur tailings, promote the release of active silica and aluminum. More hydration product gel is formed in the gel system to improve the pore structure of geopolymer, thus improving the compressive strength of sulfur tailings-based geopolymers. The above experimental results indicate that alkaline hydrothermal activation is a method that can effectively improve the activity of sulfur tailings.

Solid Waste and Eco-Materials

Preparation and Properties of Rice Husk Ash Substitute Micro Expansion Synchronous Grouting Material

ZHU Juntao, ZHANG Feilong, LI Ke, HE Wei, LI Ming

2024, 43(10):  3715-3725. 

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In order to solve the cost and environmental pollution problems caused by the transportation and stacking of shield tunneling muck, and to achieve the goal of resource reutilization of solid waste, a study was conducted based on a section of the Zhengzhou Metro Line 10 shield tunneling project. Excavated muck was used to replace sand, fly ash, and bentonite, while rice husk ash (RHA) was used to partially replace cement in the preparation of micro expansion synchronous grouting material. The effects of RHA content, muck particle size, water-binder ratio, and the type and content of expansion agents on the working and mechanical properties of synchronous grouting material were investigated. The results indicate that RHA significantly affects the slurry consistency and setting time, and higher RHA content leads to lower slurry consistency and shorter setting time. When RHA content is 25% (based on mass ratio of cement), the slurry consistency decreases by 27.5% and the setting time shortens by 39.9%. As RHA content increases, the compressive strength of slurry decreases first and then increases. As the particle size of muck increases, the slurry consistency and setting time decrease. Quicklime powder and high soundless static cracking agent (HSCA) as expansion agents reduce slurry consistency but effectively improve setting time and compressive strength. When HSCA mass fraction exceeds 3%, the expansion effect of HSCA is superior to that of quicklime powder. The tests determine that a water-binder ratio of 2.6, RHA content of 25%, adding larger particle size of muck, and the appropriate addition of expansion agents collectively meet all engineering requirements for slurry indicators, thereby providing a novel approach for the reutilization of shield tunneling muck and rice husk ash.

Optimization Method of Slag-Fly Ash Geopolymer Grouting Material Ratio

ZHANG Yongjie, LI Jiabing, DENG Peiyu, LONG Kang, GAN Zetong, TIAN Xiang

2024, 43(10):  3726-3735. 

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As a green, environmentally friendly, and cost-effective grouting material, geopolymer requires consideration of grouting performance indicators such as strength and fluidity in order to achieve good injectability.For this reason, indoor ratio optimization experiments were conducted using liquid-solid ratio, water glass content, and water glass modulus as experimental factors. A multivariate second-order response surface regression model was constructed for compressive strength, flowability, and final setting time, and the influences of single factor and its interaction on various grouting performance indicators were obtained through variance analysis. The degree of influence of experimental factors on grouting performance indicators is as follows: liquid-solid ratio, water glass content, and water glass modulus. The interaction between liquid-solid ratio and water glass content has a significant impact on compressive strength, while the interaction between the other two factors has no significant impact on grouting performance indicators. Using the analytic hierarchy process and expert assignment method to obtain the relative weights of various grouting performance indicators, a multi-objective satisfaction function was constructed to optimize the ratio of slag-fly ash geopolymer grouting materials. Based on this, SEM testing was conducted on the slurry stone body with the best comprehensive ratio of grouting performance indicators. The results show that a small number of spherical unreacted fly ash particles can still be observed in the system, the slag particles and cement particles are basically fully reacted, and the oligomeric gel-like reaction products are rearranged and extended by deposition, and cross-lap with each other to form a dense and complete spatial network-like structure.

Long Term Leaching Behavior of Heavy Metals in Gold Tailings Concrete

LUO Zuoqiu, LI Xiaoguang, ZHANG Kaifeng, FU Wanzhang, TONG Xiaogen, MENG Gang

2024, 43(10):  3736-3744. 

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An investigation was undertaken to assess the potential for heavy metal leaching from gold tailings (GTs) when used GTs as fine aggregate for concrete. The leaching behavior in different pH leaching solutions and long-term leaching features of gold tailings concrete were studied. A kinetic model was used to predict the total amount of heavy metal leaching that will occur in next thirty years. The results reveal that the levels of Ba, Cd, Cr, Pb, Mn and Cu in GTs exceed the natural levels of these elements found in Chinese soil. Significantly, the leaching of Ba, Cd, Pb, Mn and Cu is more evident. GTs content shows a positive correlation with the leaching amount of heavy metals, and the cumulative leaching amount of heavy metals drops dramatically after 16 d. Based on 30 years leaching amount prediction, the leaching amount of Pb, Cu and Ba is 2~3 mg/L, while the leaching amount of Cd, Cr and Mn is less than 1 mg/L. These findings indicate that the GTs is sufficiently cured in concrete, thereby reducing the risk of long-term leaching of heavy metals.

Mechanical Properties of Hybrid Fiber-Reinforced Recycled Coarse Aggregate Concrete Based on DIC Method

HU Jiyuan, SHENG Dongfa, QIN Feifei, HUO Xiaowei, CHAI Zhengyi

2024, 43(10):  3745-3754. 

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To investigate the basic mechanical properties of hybrid fiber-reinforced recycled coarse aggregate concrete (HFR-RCAC), 45 sets of specimens were prepared for compressive, split tensile, and flexural tests, with the volume of steel-polypropylene hybrid fibers (HF) (0%, 0.5%, and 1.0%) and the mass substitution rate of recycled coarse aggregate (0%, 25%, 50%, 75%, and 100%) as the main test parameters. The full-field displacement and strain of specimen surfaces were monitored with the help of digital image correlation (DIC) method, and the microstructure of the interfacial transition zone between polypropylene fibers and recycled coarse aggregates was observed by scanning electron microscope (SEM). The test results show that the mechanical properties of HFR-RCAC decreases with the increase of the replacement rate of recycled coarse aggregate, and the incorporation of fibers can compensate for the loss of strength caused by the recycled coarse aggregate, which can significantly improve its mechanical properties. The full-field strain evolution of the compressive damage of specimen was obtained by DIC method, and the dynamic evolution characteristics of macro- and microscopic cracks on the surface of specimen were analyzed based on the evolutionary process of maximum principal strains, and the enhancement of concrete by HF is mainly manifested in the form of hindering the expansion of macro cracks. The microstructural changes in the transition zone of polypropylene fiber-cement matrix interface were characterized by SEM, which explains changes in the mechanical properties of HFR-RCAC as well as the fiber-modified reinforcing mechanism from a microscopic point of view.

Mechanical Strength Growth Law and Prediction Model of Cement Stabilized Macadam with Construction Waste

ZHANG Yu, JIANG Yingjun, FAN Jiangtao, XU Xiaoping, YU Xiaosong

2024, 43(10):  3755-3764. 

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The effect of dosage of recycled aggregate from construction waste on the mechanical strength ofcement stabilized macadam (CSM) was investigated, the optimal dosage and proportion of recycled aggregate were proposed based on the principle of the highest strength or the maximum dosage. The growth law of mechanical strength of cement stabilized macadam recycled aggregate (CSMRA) was investigated under the optimal dosage, a prediction model of mechanical strength of CSMRA was proposed, and the reliability of prediction was verified. The results show that the compressive strength of CSMRA increases and then decreases with the increase of recycled fine aggregate dosage, decreases with the increase of recycled coarse aggregate dosage, and the maximum dosage of recycled aggregate is 70% (mass fraction). The correlation coefficient of established mechanical strength growth equation and prediction model is more than 0.98, and the error between predicted value and measured value is no more than 14.0%. This indicates that the model can accurately predict the mechanical strength of CSMRA at other ages after determining cement dosage, aggregate type, mineral proportion and 7 d strength.

Mechanical Properties and Toxic Leaching Characteristics of Alkali-Activated Chelated Municipal Solid Waste Incinerator Fly Ash

LU Shilin, DING Xiuming, LUO Qi, YE Weikai, DONG Faxin, WU Peixi, MA Jun, WANG Junfeng

2024, 43(10):  3765-3771. 

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After the chelation and solidification of municipal solid waste incineration fly ash, there are still certain environmental hazards. Landfilling will occupy a large amount of land, and reusing can alleviate the pressure on landfill site. This article used alkali activation technology to prepare chelated fly ash mineral powder based alkali-activated cementitious material. In addition to exploring the feasibility of alkali-activated chelated fly ash, the influence of calcium oxide content on improving the performance of cementitious material was also explored. The results show that the compressive strength of solidified body is highest when calcium oxide content is 4% (mass fraction), while the compressive strength of solidified body slowly decreases when calcium oxide content exceedes 4%. The addition of calcium oxide promotes the formation of hydration products of C-S-H gel and significantly improves the compressive strength of material. Meanwhile, through leaching tests, it is found that the heavy metal leaching concentration of solidified body doped with calcium oxide is lower than that of solidified body without calcium oxide, and meets the limit values specified in “Standard for pollution control on the landfill site of municipal solid waste” (GB 16889—2008).

Ceramics

Research Progress of Mechanism and Process of Thermal Debinding in 3D-Printed Ceramic Green Body

LUO Huangyang, YANG Xianfeng, LIU Ziyu, LIU Peng, XU Xiewen, XIE Zhipeng

2024, 43(10):  3772-3786. 

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Organic binders are always necessary for the fabrication of advanced ceramics by 3D-printing, which are mainly discharged from the ceramic green bodies through a thermal debinding process. Thermal debinding process of organic binders thus has a significant impact on the quality of 3D-printed green bodies and is crucial for fabricating high-quality advanced ceramics to implement applications. Theory and practice in the thermal debinding process of the representative 3D-printed green bodies were reviewed.Based on the composition and function of organic binders, the heat removal methods of different molecular weight organic binders were compared. The interaction between organic binders and ceramic particle surface and the effect of degreasing atmosphere on thermal degradation of organic binders were discussed. Then the thermal debinding process was divided into three stages and the development of the green body structure was described. Three mass transfer channels were analyzed: liquid was transferred by the capillary force, vapor diffused in the liquid phase, and vapor diffused or permeated through the pore nets. Origin causes of the defects such as cracks and distortion lying in the thermal debinding process and the previous steps were analyzed and some control measures were put forward.

Modulation of HA-Al₂O₃ Composite Ceramic Paste and Its High Precision Curing Performance

LIU Qiuyu, LI Zhiwei, WANG Ao, WANG Zhihao, WANG Yulan, CHEN Fei

2024, 43(10):  3787-3797. 

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High-strength alumina (Al₂O₃) was utilized as a reinforcing phase to improve the strength of hydroxyapatite (HA), a bioactive material, but the HA-Al₂O₃ ceramics prepared by traditional hydrothermal method could not achieve the precise control of pore size and porosity, whereas the light curing additive manufacturing technology could achieve the high precision molding of HA-Al₂O₃ ceramics through the high-performance photocurable slurry. The state of HA-Al₂O₃ slurry is adjusted by the addition of dispersant, photoinitiator, and photoabsorbent to alleviate the severe scattering effect caused by the refractive index mismatch between HA powder, Al₂O₃ powder, and photosensitive resin. In this study, the effects of the type and content of photoinitiator and dispersant on the slurry were explored. The rheological and curing properties of the slurry are first improved and then weakened with the addition of both, and the optimal dosages of photoinitiator and dispersant are 0.5% and 4% (mass fraction), respectively. The effects of two light absorbers, graphite and methyl yellow, on improving the printing accuracy were compared. Although graphite improves the printing accuracy and rheology of the slurry, it reduces the printing quality, so the dosage of 5.0×10^-5 methyl yellow is determined, and finally HA-Al₂O₃ slurries suitable for high precision printing are obtained.

Modification and Spontaneous Coagulation Casting of Domestic Calcined Alumina Powder

LIAO Lixuan, LIU Wenlong, JI Haohao, MAO Junyan, ZHANG Jian, MAO Xiaojian, WANG Shiwei

2024, 43(10):  3798-3806. 

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Al₂O₃ ceramics are the most widely used structural ceramics because of excellent mechanical properties, acid and alkali corrosion resistance and high quality-price-ratio. Due to serious agglomeration and high content of sodium and potassium impurities in domestic calcined Al₂O₃ powder, the preparation of Al₂O₃ ceramics with high performance relies heavily on imported powder. In this work, the Al₂O₃ powder produced by a domestic company was firstly disaggregated using ball milling, and the median particle size D₅₀ of the powder was reduced from 1.88 μm to 0.90 μm. Afterwards, the impurity content in the powder was reduced by washing with water, and the Na content was reduced from 140×10^-6 to 60×10^-6, which was close to the level of the same grade powder abroad. Finally, Al₂O₃ ceramic green bodies were prepared by spontaneous coagulation casting using MgO and MgAl₂O₄ as sintering aids. It is found that the addition of MgO increases the slurry viscosity, while MgAl₂O₄ does not affect that, and both can effectively reduce the sintering temperature and inhibit the grain growth. And the average grain size is reduced from 41.10 μm to 10.64 μm, which improves the mechanical properties of Al₂O₃ ceramics. Through disaggregation and purification, the domestic Al₂O₃ powder can reach the same level as the Japanese Sumitomo Al₂O₃ powder with the best performance in the same grade.

Research of High Sensitivity Piezoelectric Ceramics Based on Pb(Sb_1/2Nb_1/2)O₃-Pb(ZrTi)O₃

GAI Xuezhou, WU Fan, WANG Yuequn

2024, 43(10):  3807-3713. 

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It is of great practical significance to improve the sensitivity and enhance the stability of lead zirconate titanate (PZT) piezoelectric ceramics under hydrostatic pressure condition. In this work, the xPb(Sb_1/2Nb_1/2)O₃-(1-x)Pb(Zr_0.52Ti_0.48) (PSN-PZT, x=0.018, 0.020, 0.022, 0.025, 0.030) piezoelectric ceramics were prepared with conventional solid-state method. The influence of PSN on the phase, microscopic morphology, curie temperature, dielectric property, ferroelectric property, and piezoelectric properties of ceramics has investigated. The sensitivity of PSN-PZT and traditional high sensitivity piezoelectric ceramics was measured comparatively within the hydrostatic pressure of 5～30 MPa. The results show that the incorporation of PSN can improve the sensitivity and enhance the hydrostatic figure of merit (HFOM) of PZT piezoelectric ceramics significantly. When x=0.020, the PSN-PZT ceramics have the best electric properties, planar electromechanical coupling factor k_p=0.641, longitudinal piezoelectric strain constant d₃₃=325 pC/N, transverse piezoelectric voltage constant g₃₁=16.642 mV·m·N^-1, isostatic piezoelectric voltage constant g_h (5 MPa)=9.91 mV·m^-1·Pa^-1, HFOM (5 MPa)=679×10^-15 Pa^-1.

Residual Stress Analysis and Regulation of Diamond Thin Films on AlN Ceramics Substrates

SHI Yunlong, LIN Rongchuan, WEI Shasha, SUI Yusheng, DONG Tianlei

2024, 43(10):  3814-3823. 

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The research aims to investigate the generation and distribution of the residual stress in diamond thin films and explore methods of relieving it. Firstly, the finite element analysis software ANSYS Workbench was used to simulate the thermal stress of diamond thin films during the cooling process, and the effect of film thickness on thermal stress was studied. Then through the microwave plasma chemical vapor deposition (MPCVD), diamond thin films of varying thicknesses were deposited on aluminum nitride (AlN) ceramics substrates. The cooling duration was manipulated and annealing treatments were conducted. Characterization analyses were finally carried out using SEM and Raman spectroscopy. The simulation shows that after the cooling process, the distribution of thermal stress is irregular, with the maximum principal stress being tensile stress and the minimum principal stress being compressive stress. As the thickness of diamond thin films increases, the maximum principal stress shows an ascending trend, reaching a peak value of 373 MPa when the film thickness is 200 μm, which is close to the normal fracture strength range of diamond thin films (400~700 MPa). Conversely, the minimum principal stress and shear stress exhibit a decline as the film thickness increases. Raman characterization indicates that the surface of the diamond thin films has residual compressive stress. This residual stress decreases with increasing film thickness and cooling duration. After in-situ annealing at 600 ℃ in a hydrogen atmosphere, the stress-induced distortion in the films is alleviated, and there is a noticeable enhancement in the intensity of the diamond phase Raman peak.

Glass

Research Progress on Glass-Based Neutron and Gamma-Ray Shielding Materials

SONG Zifeng, WANG Chen, ZHANG Yong

2024, 43(10):  3824-3833. 

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Glass-based materials are renowned for their application prospects in neutron and gamma-ray shielding, focusing on their dual functionality of offering radiation protection while permitting visual monitoring. These materials stand out for their excellent chemical durability, resilience against radiation-induced deterioration, high refractive indices, and superior light transmission characteristics. In this paper, the initial sections are delved into the shielding mechanisms for neutron and gamma-ray radiation, employing Monte Carlo simulations to elucidate the design principles and development strategies of these shielding materials. It is complemented by a comprehensive review of the current state of research in glass-based shielding materials. Given the environmental and health concerns associated with lead-based glasses, lead glass is being abandoned. The paper highlights the predominance of silicate, borate, and borosilicate glasses in the industry. It is demonstrated that the addition of heavy metal oxides (such as Bi₂O₃ and BaO) and rare earth elements (like La and Gd) to the glass matrix can significantly increase the mass attenuation coefficient (MAC), reduce the half-value layer (HLV), and thereby enhance shielding effectiveness. Notably, the integration of these dopants may negatively impact the mechanical properties of materials. This paper also includes a comparison of glass-based shielding materials with alternative shielding solutions. Enhancing the multifaceted performance of glass-based shielding materials, alongside the advancement of eco-friendly and smart shielding solutions, will constitute a pivotal area of future research.

Sintering-Crystallization Behavior and Properties of Low Expansion Lithium Aluminosiliate Glass-Ceramics

CHEN Dandan, LYU Dajuan, CHEN Qiao, LIU Jia, HAN Jianjun, WANG Jing, LI Luyao

2024, 43(10):  3834-3842. 

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Low expansion Li₂O-Al₂O₃-SiO₂ (LAS) glass-ceramics were prepared using sintering method. The effect of ZnO partially substitution for Li₂O on the microstructure, sintering behavior, crystallization behavior and properties of LAS glass-ceramics was investigated. The results show that the substitution of ZnO for Li₂O reduces the initial crystallization temperature of LAS glass-ceramics,leading to significant amount of Li₂Al₂Si₃O₁₀ phase precipitating out after holding at 800 ℃ for 10 min, which hinders the sintering shrinkage of glass. In contrast, the LAS glass-ceramics without ZnO exhibits slower crystallization at 800 ℃, which is beneficial for sintering densification process. When the sintering temperature is 1 100 ℃, the main crystalline phase present in glass-ceramics is identified as β-spodumene. The coefficient of thermal expansion of glass-ceramics without ZnO is 1.747×10^-6 K^-1, the flexural strength is 138.4 MPa, the dielectric constant is 3.52 and the dielectric loss is 0.001 6.

Effect of CuO on Crystallization Behavior and Microwave Dielectric Properties of Cordierite Glass-Ceramics

ZHANG Jie, CHEN Qiao, LIU Jia, LI Luyao, WANG Jing, HAN Jianjun

2024, 43(10):  3843-3851. 

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The xCuO-(22.2-x)MgO-22.2Al₂O₃-55.6SiO₂ (x=0, 0.25, 0.50, 0.75 and 1.00, molar fraction) (MAS) glass-ceramics were synthesized using sintering-crystallization method. The effect of CuO content on the crystallization behavior, crystal type, micromorphology and microwave dielectric properties of MAS glass-ceramics was studied. The results show that as the CuO content increases from 0% to 1.00%, substituting for MgO, the glass transition temperature decreases. Additionally, the precipitation peak temperatures also show a decreasing trend, while the Avrami index n gradually increases. The primary crystalline phase in glass-ceramics is α-cordierite. The inclusion of CuO facilitates the transformation of μ-cordierite to α-cordierite at lower temperatures and reduces the thermal expansion coefficient. With the increase of CuO content, the dielectric constant of glass-ceramics increases first and then decreases, while the dielectric loss decreases first and then increases. At a heat treatment 650 ℃/2 h+1 050 ℃/2 h, the glass-ceramics doped with 0.25% and 0.50% CuO exhibits optimal integrated dielectric properties, which dielectric constant is 5.04 and 5.07, dielectric loss is 7.49×10^-4 and 7.12×10^-4, and quality factor is 20 013.35 and 20 786.41 GHz within the frequency range of 14.6~15.2 GHz.

Defect of 532 nm Nanosecond Laser Hole Cutting in Float Glass

FU Min, LI Bo, LI Wenyuan

2024, 43(10):  3852-3857. 

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Efficient cutting of float glass can be achieved by using 532 nm nanosecond laser with the bottom-up spiral scanning method. Due to the obvious thermal effect when the nanosecond laser acts on the glass, it will cause glass edge chipping, white spots on the side wall surface, surface micro cracks and voids and other defect behaviors. Focusing on this problem, the single-factor experimental method was used to explore 532 nm laser hole cutting defect behavior. The results show that the laser pulse frequency is the key factor affecting the defect shape. Improper pulse frequency and pulse energy will seriously increase the glass edge chipping and the surface roughness of hole wall, and also produce uneven regional white spots. Increasing the scanning speed will reduce the surface roughness of hole wall. Smaller spiral overlap rate will cause the corrugated surface morphology of glass hole wall. When the hole wall quality is poor, the micro cracks and voids are more obvious.

New Functional Materials

Research Progress on Influences of Cations on Preparation of Calcium Sulfate Hemihydrate Whiskers

HU Xiaoting, ZHOU Yutao, LIU Yongmei, GUO Jiemin, MENG Xiufang, SHEN Shuguang

2024, 43(10):  3858-3864. 

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The effects of soluble ions on the morphology and crystal growth of calcium sulfate hemihydrate whiskers are very significant. In order to gain a deeper understanding of the basic theory of regulating whiskers, this paper summarises the progress of research on the effects of different types and concentrations of soluble cations in desulfurization gypsum on the whisker preparation. The low concentration of Na⁺ has a small effect on the calcium sulfate hemihydrate whiskers and barely affects the morphology and surface smoothness of the whiskers. The content of K⁺ is suitable to be 3% (mass fraction) or below, and the higher content has a detrimental effect on the growth of calcium sulfate hemihydrate whiskers. Mg²⁺ makes the whisker surface more homogeneous and crystalline. And the trace amount of selective adsorption of Al³⁺ has no effect on the whisker length-to-diameter ratio. Similar to K⁺, Fe³⁺ also has the optimal concentration, which is lower than 2 mmol/L. Unlike the cations mentioned above, Cu²⁺ is not from the raw material, but is an additional ion introduced in the doping of the appropriate amount of Cu²⁺ is conducive to the formation of whiskers with a smooth and uniform surface.

Research Progress on Inorganic Adhesives for Nuclear Power System

LI Jingwei, XIANG Heng, WANG Chen

2024, 43(10):  3865-3877. 

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Adhesive materials, as one of the critical materials in nuclear power plants, play a crucial role in nuclear applications. In comparison to traditional organic adhesives, inorganic adhesives exhibit unique advantages in the nuclear field due to their excellent high-temperature stability, radiation resistance, weather resistance, and cost-effectiveness. This paper firstly provides an overview of the composition, structure, classification, and basic characteristics of inorganic adhesives, followed by a detailed exploration of the bonding mechanisms, modification strategies, and performance enhancement methods of phosphate inorganic adhesives and silicate inorganic adhesives. Research indicates that by optimizing fillers, introducing cross-linking agents, and adjusting curing agents, the high-temperature resistance of inorganic adhesives can be effectively improved. Similarly, significant enhancements in radiation resistance can be achieved through adjustments in curing processes, interfacial optimization, and the introduction of antioxidants. Additionally, innovative applications of inorganic adhesives such as preloading techniques, control of curing temperature, and special treatment of bonding interfaces are discussed. This study provides new perspectives and strategic references for inorganic adhesives application in nuclear power system, thereby facilitating the development of adhesive technology in the field of nuclear power.

Preparation and Gas-Sensitive Performance of ZnO-SnO₂ Composite Gas-Sensitive Inks for Non-Contact Dispenser Printing

WANG Jianbo, JIA Minghao, WANG Xingfeng, LEI Ming, SHEN Jie, JIN Wei

2024, 43(10):  3878-3885. 

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Non-contact dispenser printing is a novel, high-precision, template-free, and inexpensive film-forming technique. The quality of printed films is mostly determined by the physicochemical characteristics of the ink, which also have a big effect on the performance of microelectronic devices. In this work, high-performance gas-sensitive ink was made with ZnO-SnO₂ composite gas-sensitive materials as functional phases and ethylene glycol and glycerol as solvents, employing PEG400 as dispersion in place of conventional high molecular weight dispersants. ZnO-SnO₂ composite gas-sensitive films were printed on micro-electromechanical system (MEMS) micro-hotplates using non-contact dispenser method. The effects of PEG400 content and solid content on the physical and chemical properties of ink were discussed by measuring the viscosity, and suspension stability of the ink. The microscopic morphology of the film was observed by SEM. The results show that the composite gas-sensitive ink possesses printability and low-temperature sintering film-forming properties when the solid content is 15% (mass fraction, the same here in after) and the PEG400 content is 6%, and the prepared composite gas-sensitive film is uniform in thickness, with a smooth surface, regular edges, and a good response to acetone gas.