Table of Content

15 November 2023, Volume 42 Issue 11

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Cement and Concrete

Research Progress on Carbonation Behavior of Concrete with Large Volume of Mineral Admixture

LI Maosen, WANG Lu, WANG Jun, LI Xi, XU Fenlian, LIU Shuhua

2023, 42(11):  3787-3798. 

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It is imperative for the cement industry to reduce carbon emission in the context of Chinese active promotion of carbon peak and carbon neutrality goals. A large volume of mineral admixture is used in large volume mineral admixture concrete, which greatly reduces the amount of cement, so it has attracted great attention. In this paper, the carbonation behavior and microscopic mechanism of concrete with large volume of mineral admixture, and the influences of common mineral admixtures on concrete carbonation resistance were reviewed. The influence factors on carbonation of cement, the test and evaluation methods of carbonation behavior and their advantages and disadvantages were summarized. Finally, the possible ways of carbonation were proposed and the further research direction was pointed out, which is of great significance for improving the durability of concrete with large volume of mineral admixture and reducing the carbon emission of the construction industry.

Influence Mechanism of Graphite Oxide on PVA Fiber-CSH Interface Based on Molecular Dynamics

ZANG Yun, WANG Pan, WANG Muhan, WANG Xinpeng, HOU Dongshuai, ZHAO Tiejun

2023, 42(11):  3799-3806. 

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The macroscopic mechanical properties of fiber reinforced concrete are closely related to the interfacial bonding of fiber/matrix. In this paper, the effect of graphene oxide (GO) on the interfacial bonding of polyvinyl alcohol fiber (PVA)/matrix was studied by molecular dynamics simulation. The results show that when GO and PVA fiber are connected by covalent bond, the tensile force required for PVA fiber to be pulled out from concrete is the largest, and the presence of GO can improve the interfacial bonding performance between fiber and matrix. The concrete matrix and GO are mainly connected by calcium-oxygen bonds and hydrogen bonds, in which the number of calcium-oxygen bonds is large and the strength of chemical bonds is high. However, when GO and PVA fiber are physically connected, GO and PVA fiber are only connected by weak hydrogen bonds, which has a negative effect on the bonding performance of interface. In addition, GO is bound by more ionic bonds and hydrogen bonds, the atomic translational motion is reduced, and the interfacial bonding performance with matrix is improved.

Rheological Properties and Hydration Mechanism of Finely Ground Limestone Powder-Cement

DENG Guoqing, TU Linchun, ZHAO Wenhao, LI Wei

2023, 42(11):  3807-3815. 

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In order to study the effect of limestone powder fineness and dosage on the rheological properties and hydration process of cement paste, the rheological properties of freshly mixed paste were tested by Anton Paar rheometer, and the thixotropy of paste was characterized by calculating the thixotropic annulus area. Meanwhile, the mechanism of the influence of limestone powder on the rheological behavior of cement paste was explained by using the results of wet stacking density test and the calculation of the thickness of water film powder on the rheological behavior of cement paste was clarified by microcalorimetry test and quantitative analysis. Finally, the influence of limestone powder on the hydration process of cement was clarified by microcalorimetric test and XRD quantitative analysis. The results show that, at 10% dosage, the doping of 1 000 mesh (5.25 μm) stone powder reduces the yield stress by 48.4% compared with that of 400 mesh (17.34 μm) stone powder, but it improves by 15.6% compared with that of 600 mesh stone powder. At the same fineness, the doping of 10% and 20% 600 mesh (11.23 μm) stone powder reduces the yield stress of the paste by 76.7% and 81.8% compared with that of the blank group, respectively. Doping stone powder reduces the thixotropic behavior of paste and changes the variation rule of thixotropy with time. Increasing the fineness and dosage of stone powder increases the wet packing density of paste, and the thickness of water film layer, resulting in a decrease in yield stress and consistency of slurry. Increasing the fineness of stone powder can shorten the hydration induction period, move the second exothermic peak of hydration forward, and promote the early dissolution of C₃S and the generation of C-S-H, which can accelerate the hydration process of cement.

Mechanical Properties of High Cost Performance Hybrid Fiber Engineered Cementitious Composites

ZHANG Pinle, ZHU Haotian, HU Jing, ZENG Jingyuan, TAO Zhong

2023, 42(11):  3816-3826. 

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In order to improve the economic applicability of engineered cementitious composites (ECC) and ensure its good tensile ductility, the preparation method of PVA-ECC was studied, and PVA-ECC with high cost performance was prepared to provide more material selection for practical engineering. Firstly, based on the micro-mechanical model and multi-scale structural characteristics of ECC, the optimization direction of ECC mix ratio was determined. Then, the uniaxial compression test and uniaxial tensile test were carried out by designing 12 groups of ECC specimens with different mix ratios. The effects of silica fume, cement -fly ash ratio, water-binder ratio, PVA fiber type and CaCO₃ whisker on the mechanical properties of ECC were studied, and the optimal mix ratio of hybrid fiber cement-based composites was determined. Finally, the economic value of the hybrid fiber engineered cementitious composites prepared in this paper was compared and analyzed by the value engineering method. According to its cost and performance, three representative mix ratios were proposed: H12 with low cost, relatively low tensile ductility and reinforced by domestic PVA fibers, H11 with moderate cost, relatively high tensile ductility and reinforced by hybrid PVA fibers and H8 with high cost, high tensile ductility and reinforced by Japanese PVA fibers and CaCO₃ whisker. This study can provide data reference for achieving the dual goals of mechanical performance optimization and economic improvement.

Compressive Mechanical Properties and Economic Performance of Steel-PVA Hybrid Fiber Cement-Based Composites

ZHANG Pinle, ZENG Jingyuan, HU Jing, ZHU Haotian, TAO Zhong

2023, 42(11):  3827-3835. 

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Due to the high cost of fiber reinforced ductile cement-based composites (ECC), it has not been promoted in practical engineering applications. Steel fiber was added to the traditional ECC system, and Nissan PVA fiber was replaced by domestic PVA fiber according to different volume fraction (0%, 25%, 50%, 75%, 100%) to prepare cost-effective steel-PVA hybrid fiber reinforced ductile cement-based composites. The uniaxial compressive mechanical properties of hybrid fiber reinforced ductile cement-based composites were studied by cube axial compressive test. The results show that with the increase of domestic PVA fiber, the compressive strength of steel-PVA hybrid fiber cement-based composites decreases first and then increases, and the compressive toughness index increases first and then decreases, while the peak strain increases significantly. Compared with ordinary cement-based materials, steel-PVA hybrid fiber cement-based composites have better integrity and ductility. Based on the compressive properties and material cost of the composites, the domestic PVA fiber can replace the Nissan PVA fiber to configure the steel-PVA hybrid fiber cement-based composites to maximize the functional value and economic value.

Effect of SAP on Properties of High Performance Engineered Cementitious Composites

JIANG Aiguo, YANG Weibin, CAI Jie

2023, 42(11):  3836-3842. 

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High shrinkage is one of the bottlenecks limiting the large-scale engineering application of high performance engineered cementitious composites (HP-ECC). This work alleviated the shrinkage of HP-ECC by introducing superabsorbent polymers (SAP). The effects of different amounts of SAP on the compressive strength, flexural strength, tensile properties, autogenous shrinkage and dry shrinkage properties of HP-ECC were investigated. Scanning electron microscopy (SEM) was used to observe the changes in fiber surface morphology after stretching of HP-ECC caused by SAP. The results show that the addition of SAP reduces the compressive strength and flexural strength of HP-ECC and alleviates autogenous shrinkage and dry shrinkage, and the autogenous shrinkage and dry shrinkage decreases with the increase of SAP content. Moreover, SAP reduces the tensile strength of HP-ECC and increases the tensile strain of HP-ECC. The incorporation of SAP reduces the fracture toughness of the matrix, making it more prone to microcracks, thereby improving the strain hardening behavior and multiple cracking of HP-ECC. It is observed that with the increase of SAP content, the surface morphology of the fibers as they are pulled out of the matrix becomes smoother, indicating a decreasing in fiber matrix interface adhesion.

Experimental and Numerical Simulation Study on Early-Age Shear Bond Performance of Special Mortar for ALC Panel

OUYANG Deguang, ZHU Liping, GUO Xu, JING Hang

2023, 42(11):  3843-3852. 

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In order to study the early-age shear bond performance of special mortar for autoclaved lightweight concrete (ALC) panel, four groups of special mortar bonded Z-shaped specimens and one group of ordinary mortar bonded Z-shaped specimens were designed and fabricated. Through single-sided shear tests on these specimens, the shear bond strength, failure characteristics and load-slip curves of ordinary mortar bonded specimens and special mortar bonded specimens under different curing ages were analyzed, Additionally, a shear finite element model of special mortar bonded specimens was established by ABAQUS software. The results show that the early-age bond strength of special mortar is higher and develops more rapidly. After 1 d of curing, the shear bond strength of special mortar is 3.5 times higher than that of ordinary mortar of the same strength grade after 28 d of curing. With the increase of curing age, the shear stiffness and ultimate slip of the bond surface of special mortar increase slightly. Compared with the ordinary mortar, the plastic deformation capacity and the bond strength of the test block-mortar interface of special mortar are significantly improved. The load-slip curve and failure characteristics calculated by finite element are in good agreement with the test results, which verifies the effectiveness and reliability of the traction-separation law simulation of the bond behavior of special mortar.

Development and Full-Scale Tests of Modified Polyurethane-Based Seamless Expansion Joints for Bridge

LI Yan, LI Wen, ZHANG Huajian, HAN Lebing, TONG Teng, LI Xiaobo, YUAN Siqi

2023, 42(11):  3853-3865. 

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The service performance of seamless expansion joints made of polyurethane (PU) material for bridge structures was studied using full-scale tests and finite element models. First, three modified PU materials with different mix ratios were prepared. The initial setting time, tensile strength, tear strength, hardness, road adhesion, water absorption rate, resistance to rutting, and aging performance were tested and compared to determine the optimal PU mix ratio for seamless expansion joints for bridges. Then, four full-scale seamless expansion joint specimens were designed and fabricated using the selected PU material, and a corresponding finite element model was also developed. Finally, by comparing the experimental measurements and the finite element calculations, it is shown that the designed seamless expansion joint exhibits excellent service performance under uniaxial tension/compression, vertical deformation, and low-cycle fatigue loading conditions. Additionally, the research results indicate that setting a 45° inclination angle between the modified PU seamless expansion joint and the road surface could significantly improve the stress state and prevent early cracking at the joint.

Rheology and Air Void Structure of Fresh Concrete under Vibration

JIN Yang, PAN Junzheng, ZHONG Liang, HAN Yongshu, ZHOU Guangzhao, GAO Xiaojian

2023, 42(11):  3866-3877. 

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Vibration is an essential mean of concrete compaction and forming. The effect of vibration directly determines the mechanical properties and durability of hardened concrete. Based on Stokes' law, this paper proposed a new method for measuring and evaluating the rheology of fresh concrete under vibration, namely, the pulling-ball method. The correlation between the rheological parameters obtained by this method and those obtained by the rheometer at static state was analyzed, demonstrating the pulling-ball method's reliability for evaluating the rheology of fresh concrete. The results show good linear correlations between the plastic viscosity and the yield stress obtained by the pulling-ball method and those obtained by the rheometer individually. Vibration can reduce the viscous drag force of cement mortar near the internal poker vibrator by more than 90% and effectively discharge large bubbles (pore size Φ>500 μm) and retain tiny bubbles (Φ<200 μm). Vibration substantially affects removing large bubbles with increasing air-entrained agent (AEA) content. When the AEA content roses from 0.015% to 0.030% (mass fraction), the decreasing of air void content with the pore size of [500,1 000) μm increases from 31.0% to 84.8%, and those with the pore size of [1 000,2 000) μm increases from 10.3% to 36.4%.

Microscopic Characteristics of Aeolian Sand Concrete under Long Term Immersion

ZHU Suijun, WANG Jinman, WANG Xiangxiang, YANG Qiangbin, LI Genfeng, YANG Xiaotian

2023, 42(11):  3878-3883. 

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Taking aeolian sand concrete as research object, the micro-pore structure, micro-morphology and product characteristics of concrete under different aeolian sand content and different concentration of sulfate erosion were observed by nuclear magnetic resonance, field emission scanning electron microscope and energy spectrometer. The results show that with the increase of aeolian sand content, the compressive strength of aeolian sand concrete increases first and then decreases, and the porosity decreases first and then increases. When the content of aeolian sand is 40% (mass fraction), the mechanical properties are the best. With the increase of magnesium sulfate concentration and the extension of erosion period, the relative dynamic elastic modulus of aeolian sand concrete increases first and then decreases. When the concentration of magnesium sulfate is 3.5% and the content of aeolian sand is 40%, the aeolian sand concrete still meets the standard requirements after soaking for 360 d. At this time, the porosity of aeolian sand concrete is 2.553%, of which the proportion of less harmful and harmful pores reaches 63.8%, and more needle-like ettringite is produced. When the concentration of magnesium sulfate is 5.0% (mass fraction), the porosity increases to 2.879%, the proportion of less harmful and harmful pores decreases to 57.3%, and the enrichment degree of ettringite further increases.

Meso-Compressive Fracture Simulation and Performance Analysis of Steel Fiber Reinforced Concrete

TAO Xuejun, LUO Jianlin, FAN Kangxin, CHEN Jie, ZHU Min, GAO Yibo

2023, 42(11):  3884-3894. 

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Higher strength and toughness concrete infrastructures are essential for resilient city construction. There are still some challenges in the existing mesoscopic model and fracture performance simulation research of steel fiber reinforced concrete (SFRC). Here, with the secondary development of Abaqus pre-processing method aiding with Python software, a three-dimensional mesoscopic model of SFRC was established, and cohesive units were inserted globally to simulate the interface between the aggregate and concrete matrix to study the effects of volume content of steel fiber V_SF, concrete matrix strength, and particle size of aggregate on the uniaxial compressive fracture performance of SFRC. Results show that, in the range of 0% to 2.0%, the larger the V_SF is, the superior the rupture resistance of SFRC is, and the greater the residual stress is. When V_SF is 2.0%, the stress of SFRC is 60.64% higher than that of concrete without steel fiber. When the strength of concrete matrix increases, the maximum stress corresponding to C60 and C80 grade concrete increases by 66.48% and 91.39%, respectively, compared with that for C40 grade concrete, the toughness of SFRC also increases and the stress-step curve of SFRC becomes steeper in the elastic phase. In the 5~7 mm range of aggregate particle size, the rupture resistance of SFRC increases significantly with the increase of aggregate particle size. Therefore, it can be concluded that the incorporation of dispersed, non-directional ductile steel fiber into a brittle concrete matrix can effectively enhance the seismic toughness and rupture resistance of the corresponding concrete infrastructure.

Dynamic and Static Mechanical Properties of Steel Fiber Reinforced Self-Compacting Concrete after Exposed to High Temperature

ZHU Ming, GONG Nengping, MU Chaomin, CAI Tianyu, ZHANG Yu

2023, 42(11):  3895-3905. 

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In order to explore the influence of high temperature on the dynamic and static mechanical properties of steel fiber reinforced self-compacting concrete (SFRSCC), the dynamic and static mechanical properties of SFRSCC at room temperature (25 ℃) and after heat treatment at different temperatures (200, 400, 600, 800 ℃) were tested, and the numerical simulation analysis was carried out by combining LS-DYNA software and HJC constitutive model. The results show that the static compressive strength of SFRSCC increases first and then decreases with the increase of temperature grade, and reaches the maximum value of 66.9 MPa at 200 ℃. Under the same level of impact load, with the increase of temperature grade, the dynamic compressive strength of SFRSCC increases first and then decreases, and reaches the maximum at 200 ℃. The dynamic compressive strength of SFRSCC increases with the impact load level, and the dynamic strength growth factor increases with the increase of strain rate. The failure modes of simulation and test are consistent.

Anti-Clogging Performance and Clogging Model of New Self-Compacting Pervious Concrete

SHI Huarong, XUE Lu, ZHU Pinghua, SHI Zhihao, WANG Xinjie, LIU Ming

2023, 42(11):  3906-3913. 

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In order to study the influence of straight through pore diameter, water depth and horizontal runoff velocity on the anti-clogging performance of new self-compacting pervious concrete (NSPC), the permeability coefficient of NSPC after blockage and high-pressure water gun flushing was tested. Based on the probability that the blockage is captured by straight through pore, a NSPC clogging model was established. The results show that the permeability coefficient of NSPC increases with the increase of diameter of straight through pore. When the ratio of straight through pore diameter to blockage particle size is greater than 5, the particle flow formed by blockage still causes NSPC blockage. The increase of water depth reduces the permeability coefficient of NSPC after blocking. The horizontal runoff velocity has little effect on permeability coefficient of NSPC, but it delays the time of permeability coefficient reduction. The highest recovery rate of permeability coefficient of NSPC after high pressure water gun flushing reaches 85%. The established NSPC clogging model can predict the variation of the mass of blockage and the attenuation rate of permeability coefficient in straight through pore channel.

Strength Prediction Method of High Performance Concrete Based on Stacking Model Fusion

HU Yichan, LIANG Ming, XIE Canrong, XIE Weiwei, WENG Yiling, CHI Hao, PENG Hao, LUO Xueshuang

2023, 42(11):  3914-3926. 

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Strength prediction method of high performance concrete based on stacking model fusion was proposed to address the issues of large deviations and low efficiency of traditional empirical formulas for high-performance concrete strength prediction. Firstly, 1 030 sets of high-performance concrete compressive strength test data were preprocessed through data cleaning and normalization to eliminate abnormal data and the dimensional influence among data. Secondly, based on extreme gradient boosting (XGBoost), category boosting, multi-layer perceptron, and random forest (RF) algorithms, hyperparameter optimization, model training and evaluation were conducted, and the overall effect of the four base learners on strength prediction were compared and analyzed using coefficient of determination R², root mean square error and mean absolute error. Based on this, a Stacking ensemble learning model was constructed, which fuses multiple machine learning algorithms for concrete strength prediction. Finally, the model was validated using 103 sets of new data, and interpretable analysis was performed. The results show that compared to other combinations of base learners, the fusion model using XGBoost and RF significantly improves prediction accuracy and performance, and has good generalization performance. The interpretable analysis shows that the most important input feature variables are age and cement, indicating that the internal prediction logic of the model is more in line with engineering practice experience, having high rationality and reliability. The research results provide reference for further improving the accuracy of high-performance concrete strength prediction.

Life Cycle Assessment and Cost Analysis of ECC Pavement Overlay

XIONG Xiaoli, YANG Zhengxian, LUO Shengyang, LIN Jiafu, DONG Shilin

2023, 42(11):  3927-3936. 

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Compared with normal rigid concrete pavement overlay, the overlay constructed with ultra-high ductile engineered cementitious composites (ECC) has a longer service life. Life cycle assessment and cost analysis of overlayer made of six typical ECC materials were carried out. The results show that although ECC overlays do not have short-term advantages in terms of environmental impact and cost, their long-term environmental impact and cost are significantly lower than those of normal rigid concrete overlay due to their exceptionally long service life and lower maintenance frequency. Compared with normal rigid concrete overlay, ECC overlays with supplementary cementitious materials (fly ash or ground granulated blast furnace slag) and environmentally friendly fibers (polypropylene fiber or basalt fiber) reduce the global warming potential by 63.2%~68.5% within a life cycle, while their costs only account for 9.6%~23.3% of normal concrete overlay.

Influences of Different Tensile and Compressive Stress Levels on Ultrasonic Wave Velocity of Concrete

YUN Jianzhou, CHEN Shunchao, DONG Chunyan, NIE Liangpeng, YUAN Shengtao

2023, 42(11):  3937-3944. 

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In order to study the influence of stress level on ultrasonic wave velocity of concrete, plain concrete axial tensile specimens, plain concrete axial compressive specimens, plain concrete cube compressive specimens and reinforced concrete flexural members were designed and poured in this paper. The ultrasonic wave velocity tests of plain concrete specimens and reinforced concrete members under different stress levels were carried out respectively. The results show that the tensile and compressive stress levels have little effect on ultrasonic wave velocity of concrete specimens, which can be ignored. The low stress level has little effect on ultrasonic wave velocity of reinforced concrete members, and the high stress level has a great influence on ultrasonic wave velocity when cracks appear in concrete members. The tensile stress-ultrasonic wave velocity relationship curves of concrete members can be divided into four stages, including no damage period, damage development period, damage stability period and component failure period. When the tensile stress reaches 15%～25% of ultimate tensile stress, the component enters damage development period from non-damage period, and the ultrasonic wave velocity does not change at this time. When the tensile stress reaches 35%～55% of ultimate tensile stress, the component enters damage stabilization period from damage development period, and the ultrasonic wave velocity is reduced by about 5%. When the tensile stress reaches 60%～75% of the ultimate tensile stress, the component enters failure period from damage stable period, and the ultrasonic wave velocity is reduced by about 8%.

Solid Waste and Eco-Materials

Adsorption Performance of Seashell and Its Application Progress in Cement-Based Materials

WANG Dongli, XIN Rui, ZHAO Qingxin, WU Donghui, PAN Huimin, YUAN Lili

2023, 42(11):  3945-3954. 

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The use of seashells to replace traditional cement-based materials and study their adsorption capacity for pollutants can expand the functional engineering application range of cement-based materials. This paper first reviewed the principles of adsorption kinetics and adsorption isotherms to demonstrate the adsorption mechanism of seashell materials. Then the effects of pH value, contact time, pollutant concentration and other factors on the adsorption of heavy metal ions and basic dyes to seashells were discussed. Finally, the relevant applications of seashells in the construction field were reviewed. The results show that the experimental use of seashells instead of cementitious materials or natural aggregates in cement-based materials shows good adsorption capacity. The optimal pH value in the process of seashell adsorption is 5~7, the active site on the surface of seashell particles is limited, and that it would reach saturation at a certain concentration. The active site of seashell would increase with the decrease of particle size, so the seashell powder with small particle size is conducive to enhancing the absorption capacity and removal efficiency. By analyzing the adsorption performance of seashell and the applications of seashell in cement-based materials, this paper could provide ideas and methods for the design of functional cement-based adsorption materials from multiple angles.

Environmental Impact of Slag-Calcium Sulfoaluminate Cement and Analysis on Its CO₂ Mitigation Effect

PAN Zhiqiang, LI Chen, JIANG Zhengwu

2023, 42(11):  3955-3963. 

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Life cycle assessment was used to investigate the environmental impacts associated with the production of slag-calcium sulfoaluminate cement. The main sources of global warming potential (GWP) and primary energy demand (PED) were identified through sensitivity analyses. The CO₂ mitigation effect of slag-calcium sulfoaluminate cement relative to Portland cement was further analyzed. The results show that the clinker calcination stage has the highest contribution to GWP and the raw material extraction stage contributes the most to PED in the production of slag-calcium sulfoaluminate cement. Sensitivity analysis shows that the most important factors influencing GWP are limestone and coal content, and the most important factors influencing PED are coal and electricity. Compared with Portland cement, slag-calcium sulfoaluminate cement shows a significantly lower GWP and a slightly lower PED. The deficiency on mechanical properties at high slag dosages may hinder the application of slag-calcium sulfoaluminate cement as an alternative to Portland cement.

Preparation of Cement-Slag Based Early Strength Curing Agent and Macro and Micro Properties of Solidified Soil

LI Shuaikang, YU Feng, CHEN Xin, YU Jing

2023, 42(11):  3964-3977. 

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In order to improve the utilization of industrial waste residue, phosphogypsum, blast furnace slag and sodium silicate were conducted to replace part of cement stabilize silt. The regression equation of unconfined compressive strength cured for 3 and 7 d was obtained through the D-optimal mixture design, and the optimal mass ratio was calculated. The unconfined compressive strength for 3 and 7 d were separately 4.88 and 5.84 MPa by using the optimal formula to solidified soil samples. The microscopic mechanism of solidified soil was studied by X-ray diffraction and scanning electron microscopy. The results show that the hydration reaction of the optimal solidified soil is more complete than that of the cement solidified soil, the connection between the particles is more dense, and the structure is more stable. Finally, the environmental and economic evaluation of the optimal formula was carried out, and it is concluded that the formula is superior to cement in strength, environment and economy.

Preparation and Properties Characterization of Neutralization Slag Based Geopolymers

LAI Jin, LUO Qi, WANG Wenyao, HUANG Wenhao, LIU Fengyue, ZHUANG Rongchuan, WANG Junfeng

2023, 42(11):  3978-3987. 

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Neutralization slag (NS) is an industrial waste residue with calcium sulfate as the main component produced by mineral mining and metallurgical treatment processes. The large accumulation and storage of NS will pose a great threat to the environment. Therefore, it is urgent to explore a new technology for recycling NS. The mechanical properties of NS based geopolymers with different granulated blast furnace slag (GBFS) blending levels were investigated, and the phase composition, hydration rate, pore structure and micromorphology of the NS geopolymer were characterized by X-ray diffraction, reaction heat testing, mercury intrusion porosimetry, Fourier-transform infrared spectroscopy testing and scanning electron microscopy. The results show that the main product of the geopolymerisation between NS and GBFS under the action of activator is C(N)-A-S-H gel. The incorporation of GBFS can increase the rate of polymerization reaction, generate more geopolymer gels, make the microstructure of NS based geopolymer denser and the mechanical properties higher. The 28 d compressive strength of the NS based geopolymer with 30%(mass fraction) granulated blast furnace slag can reach 17.8 MPa.

Solid Waste and Eco-Materials

Freeze-Thaw Resistance and Reliability Analysis of Iron Tailings Sand Foam Concrete

ZHU Liping, DU Xiaoli, ZOU Tianmin

2023, 42(11):  3988-3995. 

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In order to study the freeze-thaw resistance of iron tailings sand foam concrete, five groups of foam concrete with a target density of 900 kg/m³ were prepared. The mass loss, strength loss, pore area rate and microstructure of foam concrete with different iron tailings sand content after freeze-thaw cycle in sulfate environment were compared and analyzed. Taking the mass loss and strength loss as the measurement indexes, the optimal mix ratio was selected, and the reliability analysis and residual life prediction were carried out based on the Wiener degradation process. The results show that during the sulfate freeze-thaw cycle, the surface of foam concrete is damaged, the internal pores are connected to form cracks, and the mass of each specimen increases first and then decreases. The compressive strength and pore area rate continue to decline, and the addition of fine iron tailings sand effectively alleviates the damage of foamed concrete. Among them, the foam concrete with 20% (mass fraction) iron tailings sand content has the strongest freeze-thaw resistance, and the specimen fails after about 300 freeze-thaw cycles. This study can provide ideas for the application of foam concrete in frozen soil areas.

Performance and Action Mechanism of Slag-Carbide Slag Based Geopolymer

AN Sai, WANG Baomin, CHEN Wenxiu, WANG Xiaojun

2023, 42(11):  3996-4005. 

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With ground granulated blast furnace slag as the main material, a slag-carbide slag based geopolymer was prepared under the excitation of alkaline carbide slag. Through XRD, SEM, EDS, FTIR, TG-DSC and other microscopic testing techniques, the performance and action mechanism of the slag-carbide slag based geopolymer were analyzed, and the heavy metal leaching test was carried out for the geopolymer. The results show that when the mass fraction of carbide slag is 14% and the water to cementitious material is 0.34, the compressive strength of the slag-carbide slag based geopolymer is 31.8 MPa under the condition of 4 d ambient temperature curing and 32 h steam curing. The hydration products of geopolymer are mainly calcium aluminosilicate hydrate, calcium carboaluminate hydrate and a small amount of ettringite crystals. The concentration of heavy metals in the leaching solution meets the national toxicity control standard, indicating the safety of geopolymer. Carbide slag has good effect on alkali activation of slag.

Composite Experiments Design, Mechanical Properties and Microstructure Analysis of Solid Waste Composite Grouting Material

ZHANG Huifang, GONG Linyang, REN Yana, HUANG Jianguo, KOU Bin, YAN Zhengwei, ZHANG Zhanchao, LIU Weijie, WEI Wenbo

2023, 42(11):  4006-4016. 

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In order to improve the utilization rate of solid wastes such as fly ash, slag, iron tailing sand and manufactured sand and prepare early strength and slightly expansive high-strength grouting material, the mechanical properties and microstructure of grouting materials were analyzed under the joint action of solid waste composite materials by mixing ordinary Portland cement and sulphoaluminate cement, designing the ternary composite system of quartz sand, iron tailing sand and manufactured and orthogonal test. The test results show that the optimal mass mix ratio of ordinary Portland cement and sulphoaluminate cement is 4 ∶1, the optimal mass mix ratio of quartz sand, iron tailings sand, limestone manufactured sand is 7 ∶1 ∶2, and the influence degree of four factors on strength of grouting materials from large to small in the orthogonal test is water binder ratio, fly ash content, binder sand ratio and slag content. Through range analysis, the optimal factor level combination is water binder ratio is 0.33, binder sand ratio is 1.0 ∶1.2, and the fly ash content and slag content are 6% and 10% (mass fraction), respectively. Through the analysis of XRD and SEM, it is found that the density of C-S-H gel will affect the strength of grouting material. The water binder ratio has an effect on the phase of ettringite, and ettringite and tricalcium aluminate hexahydrate can improve the early strength of specimens.

Effects of Industrial Solid Waste Powders on Performance of High-Performance Self-Compacting Concrete

HE Xiang, QIAO Xiantao, YU Peng, ZHOU Jiale, NIU Jiandong

2023, 42(11):  4017-4026. 

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In order to investigate the influence mechanism of various industrial solid waste powders on the mechanical properties and durability of high-performance self-compacting concrete (HPSCC), an experimental investigation was conducted on the concrete with various mass fraction of fly ash, furnace slag, lime powder, coal gangue powder and marble powder. The slump flow, T50 flow time, L-box and V-funnel flow time were experimentally measured to evaluate the workability of HPSCC. The concrete mechanical properties were evaluated by measuring ultrasonic pulse velocity and compressive strength. In addition, the power consumption and water penetration depth were tested to characterize its durability. The results show that fly ash, furnace slag, lime powder, coal gangue powder and marble powder can be used to prepare HPSCC with excellent workability and durability. The allowable mass fraction of fly ash and furnace slag powder is 35% and 60%, respectively. While, the allowable mass fraction for coal gangue powder, lime powder and marble powder is 30%, respectively. The addition of fly ash significantly improves the concrete workability, with a maximum slump flow of 750 mm. Except for lime powder, the increase of other industrial solid waste powders leads to a better concrete anti-chloride ion permeability. However, the increase of industrial solid waste powders can reduce the impermeability and compressive strength of concrete. The concrete mixed with 30% lime powder shows the largest decrease in compressive strength, with a reduction of 20.8%.

Effects of Composite Crystal Modifiers on Properties of Calcined Gypsum

HAO Jianying, WANG Shengchang, CHEN Jianing, TIAN Bo

2023, 42(11):  4027-4034. 

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As a kind of solid waste, flue gas desulfurization (FGD) gypsum can be used to prepare calcined gypsum by calcining at high temperature to realize the resource utilization of solid waste. FGD gypsum was used as raw material, calcium oxide and aluminum sulfate were added as composite crystal modifiers, and calcined gypsum was prepared by calcining at 170 ℃ for 2 h. The effects of the composite ratio and dosage of composite crystal modifiers on the properties of calcined gypsum were studied, and the composite crystal conversion mechanism was revealed. The results show that when the content of composite crystal modifier is 1% (mass fraction) and the composite ratio of calcium oxide and aluminum sulfate is 1 ∶1 (mass ratio), the prepared calcined gypsum has the best property. The gypsum block is dense after hydration, and the hydration products are in the form of alternating short columns or fibers. The 2 h flexural and compressive strength of calcined gypsum are 3.6 and 9.7 MPa, the dry flexural and compressive strength are 6.8 and 23.5 MPa, which meets the requirements of grade 3.0 calcined gypsum in Calcined Gypsum (GB/T 9776—2022).

Mechanical Properties and Mechanism of Desulphurized Gypsum-Waste Cement Carbonized Recycled Block

LIU Mingdi, QIN Ji, DONG Chen, ZHU Ying

2023, 42(11):  4035-4041. 

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In this paper, the recycling of waste cement is the research goal, a desulphurized gypsum-waste cement system was constructed, and the effect of carbonization on the mechanical properties and apparent density of the desulphurized gypsum-waste cement system was evaluated. The composition, chemical structure and morphology changes of the recycled blocks were revealed by XRD, FTIR and SEM. The results show that the carbonization of waste cement can proceed smoothly in the presence of gypsum. The carbonization process can effectively improve the compressive strength of desulphurized gypsum-waste cement samples. When the water-cement ratio is 0.4 and the waste cement content is 60% (mass fraction), the compressive strength of carbonized sample increases by 108.3% compared with that of the uncarbonized sample. When the water-cement ratio is 0.8 and the waste cement content is 65% (mass fraction), the compressive strength of carbonized sample increases by 270.0% compared with that of the uncarbonized sample. The chemical structure and microstructure of carbonized products can be controlled by adjusting water-cement ratio and waste cement content. The carbonization process can promote the hydration of waste cement, enhance the mechanical properties of the system, and reduce the apparent density of the block. The research results will provide a new idea and a reliable recycling scheme for the comprehensive utilization of waste cement and desulphurized gypsum.

Compressive Strength and Microscopic Damage of Recycled Sand/Powder Concrete

MA Quan, XIAO Jianzhuang, TIAN Feng, YAN Wenpin, SONG Min, FU Jie, YANG Chao, CAO Xue

2023, 42(11):  4042-4050. 

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To investigate the mechanical properties and microscopic damage evolution of recycled sand/powder concrete, ABAQUS based on Python language was used to establish a multi-phase three-dimensional finite element model considering virgin aggregate, old/new mortar matrix and corresponding interfacial transition zones. The effectiveness of the model was verified by compressive tests on recycled sand/powder concrete samples. The results show that the microscopic model of recycled sand/powder concrete established in this study efficaciously simulates its mechanical properties and microscopic damage circumstances. The discrepancy between the measured and simulated compressive strength is minimal, not exceeding 10.65%. The destruction of recycled sand/powder concrete specimen is generally in an “X” shape, which is fundamentally consistent with experimental phenomenon. The initial damage emerges in interface transition zone and subsequently develops progressively until it penetrates. As the content of recycled fine aggregate and recycled micro powder increases, the extent of damage expansion becomes more severe, and its mechanical properties correspondingly decline.

Effect of Mixed Recycled Sand Powder on Frost Resistance and Dry Shrinkage of Cement-Stabilized Aggregates

XIE Xiangbing, SIMA Xiaoqing, ZHANG Yilin, WANG Kaiwei, JIANG Bingyang, LIU Chenchen, LI Guanghui

2023, 42(11):  4051-4062. 

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Construction solid waste can now be recycled and used in a more environmentally friendly manner by utilizing the sand powder created during the process of crushing it into recycled aggregate. This recycled sand powder has beneficial filling and volcanic ash effects. In this study, mixed recycled sand powder (recycled composite micronized powder, recycled fine aggregate), and recycled coarse aggregate were produced using discarded bricks and concrete as raw materials. The study examined the effect of mixed recycled sand powder on the durability of cement-stabilized aggregates. The ideal composition of mixed recycled sand powder was determined using the orthogonal test method, along with indoor compaction tests, freeze-thaw tests, and dry shrinkage tests. The influence mechanism of mixed recycled sand powder on the durability of cement-stabilized aggregates was revealed using scanning electron microscope (SEM) in conjunction with energy spectrum analysis. The results show that the compressive strength loss of specimens after freeze-thaw cycle is smaller than that of benchmark specimen, with a maximum decrease of 11.63%, and the maximum increase of dry shrinkage strain is 69.75%. Mixed recycled coarse aggregate has the most significant impact on the optimal moisture content and frost resistance of cement-stabilized aggregates. Mixed recycled fine aggregate reduces the deformation resistance of specimen and has a significant effect on its dry shrinkage. Mixed recycled sand powder can effectively improve the density of mixture. The volcanic ash effect reduces the Ca/Si ratio of specimens by 52.83%. Variance analysis identifies that the ideal replacement amount of mixed recycled composite micronized powder, recycled fine aggregate, and recycled coarse aggregate is 40%, 20%, and 40% (mass fraction), respectively. These research findings can serve as a guide for recycled materials in the base layer of cement-stabilized aggregates used in road construction.

Basic Mechanical Properties and Compressive Stress-Strain Curves of Basalt Rubber Concrete

JIANG Tianhua, MO Dingcong, WAN Congcong, LU Xugang, LI Suzhu

2023, 42(11):  4063-4071. 

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In order to explore the influences of rubber particles and basalt fibers after interaction and coupling on the mechanical properties of concrete, considering the three main factors of rubber volume content, basalt fiber volume content and basalt fiber length, the influences of these factors on basalt rubber concrete were studied through compressive strength, axial compressive strength, splitting tensile strength and flexural strength tests. The results indicate that the increase of rubber content reduces the mechanical properties of concrete, but improves its deformation ability and reduces its brittleness. The addition of basalt fibers improves the mechanical strength of concrete, but when the content is too high, except for the tensile strength, all other strength decreases. Comprehensive analysis shows that when the rubber volume content is 10%, the basalt fiber volume content is 0.10% and the basalt fiber length is 18 mm, the mechanical properties of concrete are optimal. Based on the analysis of the compressive stress-strain curves, a compressive stress-strain constitutive model for basalt rubber concrete is proposed, which can be used as a reference for nonlinear analysis and engineering design of basalt rubber concrete components.

Mechanical Property of Bottom Ash-Tuff Based Geopolymer

WU Jianxun, JIANG Jian, YANG Yonghao, KONG Yu, ZHAN Xinyuan, LUO Zhihao, CHEN Liang

2023, 42(11):  4072-4081. 

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In order to explore the resource utilization prospects of municipal solid waste incineration bottom ash, the feasibility of preparing geopolymer from waste incineration bottom ash and tuff was investigated. The effects of bottom ash content, silicon-sodium molar ratio and alkali equivalent content on the properties of bottom ash-tuff based geopolymer were studied through uniaxial compressive strength test, XRD, FTIR and SEM. Test results show that the curing time has a great influence on the physical and mechanical properties of bottom ash-stuff based geopolymer. The optimal process parameters of bottom ash-stuff based geopolymer are bottom ash content of 20%, the silicon-sodium molar ratio of 1.7 and the alkali equivalent content of 8%. Bottom ash-stuff based geopolymer has a uniaxial compressive strength of 23.2 MPa and bulk density of 1.56 g/cm³ for curing 28 d. The main phases of bottom ash-stuff based geopolymer are quartz, sanidine, yeelimite and calcite. A large number of aluminosilicate gels are generated during the geopolymerization process, resulting in the microscopic structure of bottom ash-stuff based geopolymer shows a binding structure of small and larger particles. Toxicity characteristic leaching procedure of heavy metals in bottom ash-stuff based geopolymer meets the requirements of safety and environmental protection.

Solid Waste and Eco-Materials

Preparation and Heavy Metal Adsorption Properties of SiO₂ Nanofiber Cotton By in situ Polymerization Coating

GUO Qin, ZHANG Kaijun, CHEN Zijiao, MIAO Jinchao, LI Xuemei, MA Xin, XIAO Yuhang

2023, 42(11):  4082-4091. 

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In recent years, the removal of heavy metal ions is one of the difficult problems faced by water treatment under complex environments. Characterized by high-temperature resistance and strong acid resistance, three-dimensional SiO₂ prepared by electrospinning is an ideal precursor material for water treatment in complex environments. SiO₂@PEBS nanofiber cotton was prepared by in situ polymerization of ethylene benzenesulfonic acid and diethylbenzene monomer catalyzed by initiator azobisisobutyronitrile on three-dimersional SiO₂ nanofiber cotton as the substrate, realizing the uniform coating of polyvinylbenzene sulfonate acid on the surface of SiO₂ nanofiber cotton. The morphology and chemical composition of SiO₂@PEBS nanofiber cotton were revealed using SEM and FT-IR, and the thermal stability of the sample was tested with a thermogravimetric analyzer. The adsorption regeneration performance of nanofiber fiber wool under high temperature and acidic conditions was investigated. The results show that SiO₂@PEBS nanofiber cotton has high adsorption capacity on Cu²⁺, Cd²⁺ and Pb²⁺. Under pH value of 5.5 and initial ion concentration of 100 mg/L, the adsorption capacity of Cu²⁺, Cd²⁺ and Pb²⁺ is 73.0, 91.0 and 161.0 mg/g, respectively. At 80 ℃, the adsorption capacity still reaches 81.0, 64.0 and 123.0 mg/g, respectively. The adsorption process conforms to pseudo second-order kinetics and Langmuir isothermal adsorption, with high regeneration performance. After 10 times ion adsorption and desorption cycles, the capacity retention rates for Cu²⁺, Cd²⁺ and Pb²⁺ are 83.5%, 81.1% and 77.6%, respectively.

Ceramics

Research Progress of Al₂O₃ Fiber Reinforced Al₂O₃ Matrix Composites

SUN Jingwei, WANG Honglei, ZHOU Xingui

2023, 42(11):  4092-4112. 

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Compared with traditional metal material, Al₂O₃ fiber reinforced Al₂O₃ matrix (Al₂O₃/Al₂O₃) composites have become a new generation of thermos-structured composites for aerospace that have attracted much attention from scholars all over the world due to their high specific strength, low density, high temperature resistance and oxidation resistance. This paper introduces the commonly used Al₂O₃ fibers and their basic properties, summarizes the frequently used interfacial phases in Al₂O₃/Al₂O₃ composites and their influence on performance of composites, summarizes the preparation process of Al₂O₃/Al₂O₃ composites and their properties, and points out the future development trend of this material, aiming to provide a reference for the research of Al₂O₃/Al₂O₃ composites in China and promote the widespread application of Al₂O₃/Al₂O₃ composites in high-temperature components at the hot side of aerospace industry.

Preparation of Morphology-Controlled Gold Powder and Its Influence on Properties of Conductor Paste for LTCC

NA Hua, HAI Yun, HAN Bin, GUO Enxia, LYU Jinyu, XU Bo, ZU Chengkui

2023, 42(11):  4113-4121. 

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Gold conductor slurry is widely used in low-temperature co-fired ceramics (LTCC) because of the good stability and weldability. The surface morphology, particle size of gold powder have great impact on the gold conductor paste. With chlorinic acid as the raw material, D-isoreascorbic acid as the reducing agent and acacia senegal as the dispersant, three kinds of spherical gold powder with high purity were prepared by different experimental conditions, and their surface morphology, particle size and specific surface area were all different. The growth process of gold powder belongs to the seed-mediated growth method, and controlling the Cl^- concentration and the pH value of the reaction solution can finally obtain different morphology and particle size. The results show that the specific surface area of three kinds of gold powder are 0.740, 0.418 and 0.447 m²·g^-1, respectively. The specific surface area of gold powder significantly affects the viscosity of gold paste. Gold conductor paste for LTCC with the viscosity of 326, 209 and 214 Pa·s are prepared in the same ratio with the three kinds of gold powder as the function phase, respectively. The experimental results show that the gold conductor slurry is prepared from the gold powder made when dissolving chloruric acid in NaOH solution and adjusting the pH value to 2, as well as the setting 30%(mass fraction) diethylene glycol ether solution as agent solvent, which has the highest density, low square resistance and the highest gold wire bond strength. The square resistance and gold wire bond strength are 1.11 mΩ/□ and 8.66 g, respectively. The weldability of all the three kinds of gold conductor paste are better.

Preparation and Adsorption Performance of Fly Ash Based Porous Ceramics

BAI Lizhong, WANG Chaonan, CHENG Jun, ZHAO Zitong, GENG Jiawang, LI Xuefeng

2023, 42(11):  4122-4130. 

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The effective utilization of fly ash based porous ceramics can not only reduce the pollution of fly ash to the environment but also show high application value in wastewater treatment and other fields. In this paper, porous ceramics with excellent performance were prepared by direct molding sintering method with fly ash as the main raw material, bentonite as the binder and activated carbon as the pore forming agent. The effects of sintering temperature and activated carbon amount on the structures and properties of porous ceramics were studied. The results show that sintering fly ash and bentonite forms the porous ceramic skeleton, oxidized activated carbon forms the pores, and porous ceramics are formed under their synergetic effects. At the same time, with the increase of sintering temperature and the decrease of activated carbon amount, the apparent porosity and water absorption decrease, the bulk density and compressive strength increase. When the sintering temperature is 1 100 ℃ and the amount of the activated carbon is 60% (mass fraction), the prepared porous ceramics with good comprehensive performance can be prepared. Its apparent porosity is 61.75%, bulk density is 0.93 g·cm^-3, water absorption is 63.48%, compressive strength is 4.29 MPa. Moreover, its removal rate is 98.4% and the saturated adsorption capacity is 45.79 mg·g^-1 in the Pb²⁺ solution of 100 mg·L^-1.

Glass

Fabrication and Properties of Infrared Gradient Refractive Index GeS₂-In₂S₃-CsCl Chalcogenide Glass-Ceramics

LIU Hongjun, LI Chengkang, ZHOU Gangjie, CHEN Jinjin, LIN Changgui

2023, 42(11):  4131-4135. 

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Gradient refractive index infrared imaging system can greatly reduce the size, weight and cost of system while maintaining imaging performance, which is expected to advance the development of infrared imaging system towards lightweight and compactness. However, currently available infrared gradient refractive index optical materials are not accessible. Based on 65GeS₂-25In₂S₃-10CsCl chalcogenide glass, a gradient temperature field was used to thermally induce the precipitation of axially gradient-distributed β-In₂S₃ nanocrystals to produce a gradient refractive index transparent chalcogenide glass-ceramics. The results show that the precipitated β-In₂S₃ crystals are polycrystalline structures composed of nanocrystals with different crystallographic orientations, with a size of about 25 nm, and the size and number of crystals are closely related to gradient temperature field. The gradient refractive index chalcogenide glass-ceramics still maintain good transmission in long-wave infrared, and their maximum refractive index difference Δn reaches 0.047 at 10 μm.

Influence of Zinc Oxide on Structure and Properties of Glass-Ceramics and Solidification Mechanism of Heavy Metal Zinc

LI Nianzhe, ZHANG Yuxuan, CUI Xiutao, OUYANG Shunli

2023, 42(11):  4136-4145. 

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Using analytical pure reagents as raw materials to simulate zinc-containing smelting slag, glass-ceramics were prepared by melting method. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy were used as characterization methods,and the effect of different zinc oxide content on the formation, crystallization, physical and chemical properties of glass-ceramics was explored. The results show that the main crystalline phase of glass-ceramics is cordierite, and the addition of a small amount of zinc oxide (less than 0.5%, mole fraction, same as below) can enhance the glass-forming ability. As the zinc oxide content gradually increases (0.5%~20.0%), the integrity of glass network structure deteriorates, and the viscosity of glass decreases. The main phase of glass-ceramics is transformed from cordierite to spinel, and the crystallinity and grain size of glass-ceramics increase. Consequently, the bulk density, hardness and resistance to acid/alkali corrosion of glass-ceramics also increase. Heavy metal zinc has good curability in glass-ceramics, so the leaching concentration of zinc is much lower than the standard value, and leaching rate tends to be stable. This study provides a reference for the solidification of heavy metals through glass-ceramics.

Laser Welding of Chemically Tempered Glass and Its Mechanical Strength

ZENG Xinchang, DING Yuanjie, LIU Chuanliang, CHEN Ling, YE Shu

2023, 42(11):  4146-4153. 

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Ultra-short pulse laser has broad development prospects in the field of glass welding due to its unique advantages of high processing accuracy, small heat affected zone and high efficiency. In practical scenarios, glass often needs to enhance itself strength through strengthening to meet the reliability of its application. This article successfully realizes welding between chemically tempered glass using infrared ultra-short pulse laser. By observing the shape of welding spot with microscope, the regression equation of welding power, frequency, speed and laser welding joint size was summarized, and the accuracy of regression equation was verified. The results show that under the conditions of welding frequency 500 kHz and welding speed 10 mm/s, as the welding power increases, the mechanical strength of welding chemically tempered glass increases first and then decreases. The maximum shear stress of welding chemically tempered glass can reach 11.09 MPa, and the maximum tensile stress can reach 7.10 MPa. During laser welding, the chemically tempered glass is not only subjected to its own thermal expansion pressure but also superimposed tensile stress, so it is easier to cause damage to surrounding area.

Research Situation Analysis of Glass Ceramics Based on Visual Knowledge Graph

GAO Dangni, GUO Hongwei, WANG Yi, BAI Yun, GAO Yibo

2023, 42(11):  4154-4166. 

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Glass ceramics have attracted much attention and been widely applied because of corrosion resistance and high strength, as well as easy forming and unique optical properties. Based on SCI papers about glass ceramics from 2013 to 2022, which were divided into two stages of 2013 to 2017 and 2018—2022, the visual knowledge maps of author scientific collaboration networks and keyword clustering on glass ceramics were constructed with CiteSpace 6, and the author scientific cooperation networks, academic activity and visualization development trend were explored simultaneously. The results show that, researchers are more concerned on luminescence performance, biological activity and solid-state electrolytes of glass ceramics from 2013 to 2017. From 2018 to 2022, in addition to continuous study of biological activity of glass ceramics researchers' attention has shifted to energy conversion and alkali activation of glass ceramics. After summing up the previous results, we propose that the antibacterial properties of bioactive, high transparency luminescent and containing micro/nano crystalline phases of glass ceramics are worthy of further researching.

New Functional Materials

Research Progress on Silica Fiber-Based Thermal Insulation Materials

WU Yifan, WANG Xingtao, SUN Jinfeng, MENG Yongqiang, WAN Hongjing

2023, 42(11):  4167-4177. 

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The development of high-performance thermal insulation materials is of great significance to the development of aviation, construction, transportation and other fields. Silica (SiO₂) fiber has the advantages of low density, low thermal conductivity and oxidation resistance, and is a kind of thermal insulation material with great development potential. However, the thermal conductivity of SiO₂ fiber needs to be further reduced, so how to further improve its thermal insulation performance is an important topic. Based on the thermal insulation mechanism of SiO₂ fiber, the preparation methods and research status of SiO₂ fiber with different morphologies (solid, hollow, porous) are analyzed in this paper. The research progress of SiO₂ fiber composite with organic materials, inorganic materials is aslo summarized. At the same time, the main application fields of thermal insulation materials are briefly described. Finally, the development direction of SiO₂ fiber-based thermal insulation materials in the future is prospected.

Simulation of Electronic Structure and Magnetism Properties of S Vacancy and Tc-Doped Monolayer MoS₂

FU Sinian, ZHU Ruihua

2023, 42(11):  4178-4182. 

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Using the first-principles theory, the electronic structures and magnetic properties of S vacancies (V_S) and Tc-doped monolayer MoS₂ were investigated. Results reveal that the Tc-doped monolayer MoS₂ is a n-type semiconductor with ferromagnetism.Compared with the Tc-doped system, the introduction of V_S does not lead to a significant change in the total magnetic moment of the (Tc, V_S) co-doped system, and the magnetic moment of the doped system is mainly contributed by the Tc atom. In the 2Tc-doped system, the most stable configuration was determined by formation energy analysis. The magnetic moment of the 2Tc-doped system is 2.048 μ_B and mainly comes from two Tc atoms. The spin charge density analysis shows that the (Tc-4d)-(S-3p)-(Mo-4d)-(S-3p)-(Tc-4d) coupling chain may be the reason for the ferromagnetic coupling of the 2Tc-doped system.