Table of Content

15 July 2024, Volume 43 Issue 7

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Cement and Concrete

Research Progress on Multi-Field Coupling Damage Deterioration Mechanism of Concrete in Alpine Region

ZHANG Weidong, WANG Yuan, SONG Pengfei, WANG Yakun, LIU Qianqian, WANG Xuhao

2024, 43(7):  2317-2334. 

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In the actual service process, the concrete structure in alpine region is not only affected by vehicle load, but also by environmental factors such as salt corrosion and freeze-thaw. Under the action of multi-field coupling such as load, salt corrosion and freeze-thaw, the deterioration of concrete in alpine region involves the interaction of chemical, physical and mechanical effects. The complex chemical reaction between chloride salt and concrete produces expansive double salt, which leads to internal volume expansion of concrete and chemical damage. At the same time, freeze-thaw cycles and dynamic loads cause physical damage to concrete, and concrete deteriorates rapidly under the coupling of chemical damage and physical damage. In this paper, the research status of the influence of salt corrosion, freeze-thaw cycle and dynamic load multi-field coupling on the performance of concrete is reviewed, and the most advanced material non-destructive characterization techniques and modeling methods in this field are summarized. The prediction model of physical and chemical damage characteristic parameters is established from macro, fine and micro scales, and the damage degradation mechanism and degradation behavior prediction model of concrete under multi-field coupling are formed. Finally, the shortcomings of the current research are put forward.

Comparative Study on Hydration Process of Ferroaluminate, Sulfoaluminate and Portland Cement

LI Hongxuan, QI Dongyou, ZOU Delin, WANG Jianfeng, WANG Zhiyong, HAO Lulu, WANG Yali, ZHANG Yu, LIU Hongyin

2024, 43(7):  2335-2345. 

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Ferroaluminate cement has the characteristics of energy conservation, waste utilization, emission reduction, excellent process performance and environmental friendliness, and has gradually attracted the research interest of scholars at home and abroad. This article compared the hydration processes of three different cement systems, namely ferroaluminate cement (FAC), sulfoaluminate cement (SAC), and Portland cement (PC), through test methods such as hydration heat, XRD, TG-DTG, pore structure analysis, and SEM. The hydration products and mechanisms of three types of cement were analyzed. The results show that the 1 d strength of FAC increases by 130% compared to PC, and the 28 d strength exceedes SAC. The hydration heat release of FAC and SAC is mainly concentrated within 1 d, and the iron phase in FAC clinker can shorten the acceleration period and promote the formation of ettringite. Compared with PC and SAC, FAC hydration products contain not only ettringite, hydrated calcium silicate gel and aluminum glue, but also ettringite and iron glue, with lower total porosity, more compact structure of cement stone, and further improved strength and durability.

Sand Content and Orientation Time Influence Law of Oriented Steel Fiber Cementitious Composites

CHEN Zhuoyi, KOU Zihao, XIONG Yongming, YI Hongjian, CAO Xianhui

2024, 43(7):  2346-2354. 

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In order to study the steel fiber orientation distribution law of steel fiber cementitious composites, considering the two factors of orientation time and sand content, 32 specimens were made based on the steel fiber orientation equipment independently developed in the team. Under the constant magnetic field, the gradient orientation time and sand content steel fiber orientation tests were carried out systematically, using COMSOL finite element to simulate the magnetic field distribution of orientation tests, and using CT-X-ray scanning technology to obtain the cross-section images of different specimens. The orientation coefficient of steel fiber was calculated, and the orientation law of steel fiber under the influence of gradient orientation time and sand content were discussed. The results show that with the increase of orientation time, the orientation coefficient of steel fiber under the condition of the same sand content increases rapidly at the initial stage, and then slows down gradually and finally tends to be stable. Under the same orientation time, too high or too low sand content will adversely affect the orientation efficiency of steel fiber, and controlling the sand content at about 40% can obtain relatively ideal steel fiber orientation effect.

Performance of Silane Coupling Agent Modified Polypropylene Fiber Cement-Based Composites

SUN Jiaqi, LIU Xi, WANG Chuanlin, SU Zhiqi, LU Xin, MAI Jingmin

2024, 43(7):  2355-2362. 

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In this paper, different types (KH550 and KH560) and different concentrations (0.5%, 1.0%, 1.5% and 2.0%, mass fraction) of SCA were used to modify the surface of polypropylene fiber (PPF). The bearing capacity of SCA modified polypropylene fiber cement-based composites was studied by unconfined compressive strength test and flexural test, and the modified polypropylene fiber cement-based composites were characterized by scanning electron microscopy. The results show that KH560 modified polypropylene fiber has a great influence on the fluidity of cement-based composites, followed by KH550. On the whole, the closer the SCA concentration is to 1.5%, the greater the influence on the fluidity of polypropylene fiber cement-based composites is. With the increase of KH550 concentration, the porosity of cement-based composites generally decreases. With the increase of KH560 concentration, the porosity of cement-based composites decreases first and then increases, and the porosity is the smallest when the concentration is 1.5%. Both SCAs improve the surface roughness of PPF and achieve chemical bonding at PPF-SCA-matrix interface. The two kinds of SCA have little effect on the flexural strength of polypropylene fiber cement-based composites, but can effectively improve compressive strength. Overall, the modification effect of KH550 is better than KH560.

Uniaxial Compressive Mechanical Performance of Basalt Fiber Fabric-Steel-PVA Engineered Cementitious Composites

CHE Jialing, WU Jie, GU Jiawei, HUANG Yu, LIU Haifeng

2024, 43(7):  2363-2371. 

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The combined effect of basalt fiber fabric and hybrid short-cut fibers (steel fiber and PVA fiber, short-cut fibers overall volume fraction of 2%) on uniaxial compressive mechanical performance of basalt fiber fabric-steel-PVA engineered cementitious composites (BTR-HyECC) was investigated. Various compressive performance indicators of specimens were obtained through cylindrical uniaxial compressive tests, and stress-strain curves were plotted. The results indicate that, with a 0%(volume fraction, the same below)steel fiber content, the introduction of basalt fiber fabric significantly enhances compressive strength, peak strain, and compressive toughness of specimens. As the steel fiber content increases to 1%, compressive strength and elastic modulus of specimens reach maximum values, and when the steel fiber content is 1.5%, the deformability and compressive toughness of specimens reach optimum levels. Based on the experimental data, a uniaxial compressive stress-strain constitutive equation suitable for BTR-HyECC was established,which agree well with the experimental results.

Sulfate Resistance Performance of Cement-Based Materials Containing Limestone Powder at Low Temperature

LI Xuefeng

2024, 43(7):  2372-2382. 

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In order to improve sulfate resistance performance of cement-based materials containing limestone powder at low temperature, the sulfate resistance and mechanism of cement-based materials containing limestone powder mixed with different mineral admixtures were studied by using pulsed electrical field to accelerate sulfate erosion, observing the changes of specimen appearance and measuring the microscopic components of the corrosion material by XRD and FT-IR. The results indicate that the incorporation of mineral admixtures can enhance the sulfate resistance performance of cement-based materials containing limestone powder in low-temperature to some extent, and the inhibitory effect of combined mineral admixture is found to be more pronounced compared with single mineral admixture. However, the minimum content requirements of mineral admixtures should be met. It is suggested that, in the case of single mineral admixture, the mass proportion of fly ash or slag powder in cement-based materials should not be less than 30% and 50%, respectively. The sum of fly ash and slag powder content should be 50%~70% in the case of combined mineral admixture, and the mass ratio of fly ash and slag powder is 1.0∶1.5~1.0∶2.5. In addition, during thaumasite form of sulfate attack (TSA) of cement-based materials containing limestene powder, the diffraction peak of thaumasite is mainly formed by the rightward shift of ettringite diffraction peak, indicating that the formation of thaumasite is mainly formed by the transformation of ettringite. Therefore, the effective inhibition of formation of ettringite is the key point to inhibit TSA for cement-based materials containing limestone powder.

Microstructure Evolution Law of Cement-Emulsified Asphalt Mortar

JIN Shanshan, YANG Yuan, XU Zengmiao, ZHANG Yang, LI Xiang, YANG Kenan, ZHAN Weinan

2024, 43(7):  2383-2392. 

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By means of EDS, SEM, NMR and other test methods, the multi-modal data were deeply fused and analyzed from the perspectives of microstructure, hydration products, element distribution and pore characteristics. The evolution law of cement-emulsified asphalt (CA) mortar microstructure varying with asphalt-cement ratio (A/C) and age was studied qualitatively and quantitatively. The results show that with the increase of A/C, the CA mortar changes from a spatial structure with cement hydration products as continuous phase and asphalt as dispersed phase to a loose porous spatial structure with asphalt as continuous phase and cement hydration products as dispersed phase. The cement particles and hydration products are coated by asphalt, which seriously affects the development of pore structure. The total porosity and the most probable pore size gradually increase, the number of gel pores and transition pores decreases, and the number of macropores increases. With the increase of age, the hydration products of cement increases, the original larger pores are separated into smaller pores, the total porosity and the number of macropores and capillary pores decrease, the number of gel pores and transition pores increases, and the pore structure gradually becomes dense.

Internal Curing Properties of Acrylamide Type SAP Loaded with Nano Silica

LYU Yang, FAN Fulong, WU Yuanshuai, ZHU Yanchao, ZHANG Chengshan, LI Xiangguo

2024, 43(7):  2393-2403. 

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In this paper, nano silica (NS) loaded acrylamide-type superabsorbent polymer (SAP) was designed and prepared, and the influence of different NS loadings of SAP on the autogenous shrinkage, drying shrinkage, and mechanical properties of mortar were investigated. The results showed that acrylamide-type SAP could completely eliminated the autogenous shrinkage of mortar, and the inhibition effect of NS-loaded SAP on autogenous shrinkage decreased with the increase of NS loading, but still remained above 80%. The introduction of SAP and additional water increased the drying shrinkage of mortar, but with the increase of NS loading, NS-loaded SAP had a positive effect on mitigating the drying shrinkage. The introduction of SAP and additional water reduced the mechanical properties of the mortar, but with the increase of NS loading, the NS-loaded SAP significantly improved the mechanical properties of mortar. In particular, SAP loaded with 50% (relative to the mass fraction of acrylamide) NS had the least effect on the mechanical properties of the mortar, with only a 5.6% and 2.2% loss in compressive and flexural strength of the specimens at 28 d. TG and BSE results showed that the degree of hydration of the cured specimens within NS-loaded SAP increased significantly with the increase of NS loading, and the microstructure was significantly improved.

Crack Propagation and Damage Evolution in Polypropylene Fiber Reinforced Concrete with Cracks under Axis Compression

WANG Xueqing, LI Yongchao, ZHANG Xuerui, ZHAO Yunmeng, JIANG Yufeng

2024, 43(7):  2404-2414. 

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To investigate the effects of polypropylene fiber (PPF) content and prefabricated crack angle on the crack propagation and failure mode of concrete under compression, uniaxial compression tests were conducted on plain concrete and polypropylene fiber concrete (PFRC) with different crack angles. The internal damage process was collected using an acoustic emission (AE) monitoring system, and the failure mode and AE localization map of specimens were analyzed. The relationship between PPF content, prefabricated crack angle, stress-strain curve, AE parameters and other indicators was explored. Research has shown that as the content of PPF increases, the number and propagation range of cracks in specimen decrease first and then increase, and the peak stress increases first and then decreases. Its failure mode changes from tensile failure to tensile shear or shear failure. The mechanism of PPF is that when the content is appropriate, it can play a good bridging role inside the matrix, while when it is excessive, it is easy to form clusters, leading to an increase in internal weak surfaces, indicating that PPF has positive and negative effects on the reinforcement effect of concrete. As the angle of prefabricated cracks increases, the peak stress shows a trend of decreasing first and then increasing. Among them, there is a certain synergistic effect between inclined non horizontal angle prefabricated cracks and high content PPF, and several types of prefabricated crack angles that are sensitive to changes in compressive strength and PPF content of the specimens are found. Finally, analyzing the AE data, it is found that the addition of PPF increases the number and distribution of positioning points in the AE localization map. The activity time of AE signals from the beginning to the peak is prolonged with the increase of PPF content, indicating that PPF has a crack resistance and toughening effect on concrete.

Influence of Carbonate Environment on Performance and Microscopic Characteristics of Tunnel Concrete

LI Kang, GAO Meng, ZOU Min, LIU Juanhong, XIE Yongjiang

2024, 43(7):  2415-2426. 

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To investigate the erosion and deterioration of railway tunnel lining concrete in karstic areas, this study focuses on ordinary Portland cement concrete and calcium sulfoaluminate cement concrete, as well as shotcrete. An environment of accelerated corrosion through carbonate exposure was simulated. The impact of carbonate environment on the macroscopic properties and microscopic characteristics of different types of tunnel concrete was studied using macroscopic performance testing and microscopic testing methods such as X-ray diffraction analysis, Fourier-transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The mass, relative dynamic modulus of elasticity and compressive strength of concrete show an initial increase followed by a subsequent decrease with the increase of immersion duration. The decline starts after 180 d of immersion, in which the compressive strength of calcium sulfoaluminate cement concrete is lower than the initial value after immersing for 360 d. Microstructural analysis of the concrete reveals that after 360 d of erosion, the crystals and gels in the original hydration products of the samples sharply decrease, giving rise to a significant amount of calcium carbonate. In the samples of calcium sulfoaluminate cement concrete, [Si(OH)₆]^2- octahedral groups are detected, confirming the formation of thaumasite. The calcium sufoaluminate cement-based concrete with ettringite as the main hydration product is more significantly affected by carbonate erosion.

Preparation and Properties of Lightweight High-Strength Autoclaved Aerated Concrete

LI Xiangguo, WEI Wu, HE Chao, CAI Lixiong, LYU Yang, DAN Jianming

2024, 43(7):  2427-2433. 

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In this paper, the preparation technology of lightweight high-strength autoclaved aerated concrete was studied by using typical solid waste resources such as fly ash and micro silica powder in Xinjiang. The effects of raw material ratio, water to material ratio and gas-generating agent content on the absolute dry density and compressive strength of products were analyzed.The results show that when m (fly ash)∶m(micro silica powder)∶m(quartz sand)∶m(quicklime)∶m(cement)∶m(gypsum) is 30∶25∶10∶25∶8∶2, the amount of aluminum powder is 0.10% of total material mass, the water to material ratio is 0.58, the autoclave temperature is 195 ℃, the autoclave pressure is 1.2 MPa, and the autoclave time is 8 h, the absolute dry density of lightweight high-strength autoclaved aerated concrete is 568.70 kg/m³, the compressive strength is 5.4 MPa, and the thermal conductivity is 0.140 W/(m·K), reaching the level of A5.0, B06.

Properties of Organic Acid Activated Metakaolin Concrete

LI An, WANG Yanjun, ZHANG Zhijie, FAN Zhihong

2024, 43(7):  2434-2440. 

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Kaolin is a common clay minerals in nature and a layered aluminosilicate mineral. Small molecule oxalic acid and citric acid were selected as composite organic acids, and kaolin was subjected to acid activation treatment to prepare an organic acid activated metakaolin by high temperature calcination and mechanical grinding. The influences of organic acid activation methods on the microstructure of kaolin were analyzed through SEM and TEM, and the influence of organic acid activated metakaolin on macroscopic properties such as mechanical properties, drying shrinkage performance, electrical flux of concrete and microscopic pore structure was studied, and its microscopic mechanism of action was revealed. The results show that organic acid activation leads to the dissolution of some Si and Al in kaolin, causing damage to the edges and interlayer of the layered structure, resulting in a relatively rough microstructure. The calcination temperature decreases by 160 ℃ and the specific surface area increases. Adding organic acid activated metakaolin to concrete can improve the comprehensive performance of concrete by enhancing the compactness of concrete. The compressive strength at 28 d increases by 23.2%, and the 28 d electric flux is reduced by 51.8%, which is superior to metakaolin and silica fume.

Static Stability of Ultra-High Performance Concrete Containing Coarse Aggregate

JIANG Jian, LI Chuanxi, DENG Shuai, SIDU Yinghu, YANG Sai

2024, 43(7):  2441-2450. 

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In order to improve the overall static stability of ultra-high performance concrete containing coarse aggregate (CA-UHPC), the image analysis was employed to investigate the effects of rheological parameters of the mixture (before adding fiber), coarse aggregate content and coarse aggregate gradation on the static stability of CA-UHPC without fiber and with fiber. The results show that the overall uniformity of coarse aggregate increases with the decrease of the average initial clear distance of coarse aggregate. When the yield stress and plastic viscosity of the mixture are small, the uniformity of fiber distribution decreases due to fiber settlement. The addition of fiber reduces the overall uniformity of coarse aggregate, and the coarse aggregate also affects the uniform distribution of fiber. For the CA-UHPC system, the reduction of the average initial clear distance of coarse aggregate particles increases the distribution stability of coarse aggregate, but too low average initial clear distance between coarse aggregate particles affects the distribution of fiber. Therefore, when the content of coarse aggregate is constant, the fiber distribution coefficient can increase without affecting the stability of coarse aggregate by adjusting the coarse aggregate gradation or sand ratio.

Uniaxial Tensile and Compressive Failure Law and Mechanical Properties of Concrete after High Temperature

ZHAO Yanru, CHEN Qiang, WANG Lei, YU Wenhao

2024, 43(7):  2451-2460. 

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In this paper, uniaxial tensile and compressive tests were carried out on concrete at room temperature and after high temperature. At the same time, digital image correlation method (DIC) was used to observe the deformation evolution process of concrete specimen surface, and to explore the deformation evolution and mechanical properties attenuation of cracks in concrete during tensile and compressive processes after high temperature. The results show that with the increase of temperature, the initiation and propagation time of cracks on the surface of concrete gradually advance, the width of surface strain concentration zone and the corresponding strain value gradually increase, and the degree of crack propagation is more significant. When the temperature reaches 800 ℃, it even shows a multi-crack propagation form. The significant expansion of cracks increases the energy consumption of concrete and increases the ductility of concrete after high temperature damage. Comparing the tensile and compressive strain contours of concrete after high temperature, it can be seen that the width of strain concentration zone caused by crack cracking is similar, but the strain value of compressive specimen is slightly higher than that of tensile specimen. The initiation and propagation of cracks affect the mechanical properties of concrete. With the increase of temperature, the tensile strength, compressive strength and elastic modulus of concrete decrease continuously, and the strain at peak stress increases gradually. The tensile stress-strain curve gradually changes from two stages to three stages, and the failure characteristics change from brittleness to ductility. The compressive stress-strain curve is always three stages. Compared with uniaxial tension, the ductility characteristics of compression failure are more obvious.

Bond Stress Distribution of Steel-FRP Composite Bar Coral Concrete Beam Drawing

WANG Lei, YU Han, ZHANG Mingming, GU Jian, LU Jiahui, ZHU Dexiang

2024, 43(7):  2461-2469. 

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To study the bond stress distribution of steel-fiber reinforced polymer (FRP) composite bar (SFCB) in coral concrete, a beam pull-out test method was adopted to pull out different diameters of SFCB and carbon fiber reforced polymer (CFRP) reinforced coral concrete, and used fiber Bragg grating (FBG) sensing technology to dynamically monitor the stress distribution changes of the reinforcement material. The results of the study show that both SFCB diameter and steel core diameter affect the shape of load-slip curves. The stirrup reinforcement significantly improves the initial bonding stiffness of the reinforcement material and the strain at the loading end of the SFCB fiber layer. Stirrups to a certain extent enhance the bonding of threaded steel cores, but have little effect on the bonding of smooth round steel cores. The distribution of bond stress after SFCB yielding differs significantly from that before yielding, and the stress transfer phenomenon is more pronounced after the steel core is yielded. Due to the high elastic modulus of the steel core, the bonding stress at all points of the SFCB fiber layer bonding section is greater than that of the CFRP reinforcement under the same load.

Failure Precursory Characteristics of Early-Age Steel Fiber Reinforced Concrete under Uniaxial Compression

PAN Xiaofeng, CAO Jiantao, LUO Tao, TANG Liyun

2024, 43(7):  2470-2478. 

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Affected by hydration and external load, early-age concrete is prone to crack, which affects the durability of the structure. And the resistivity can better reflect the internal damage degree of concrete. In this study, the resistivity monitoring experiments of steel fiber reinforced concrete (SFRC) and normal concrete (NC) during uniaxial compression were carried out to study the influence of age on the resistivity variation characteristics of SFRC during uniaxial compression. The wave velocity tests of SFRC and NC at different ages were carried out. The findings indicate that the resistivity variation of SFRC during uniaxial compression is significantly influenced by age. Specifically, in the period of 28 d, the resistivity variation patterns exhibit an “L” type, a “V” type, and a “U” type. The resistivity of all specimens increases when specimens approach failure. The rate of increase is minimal at 1 and 3 d, but becomes significant at 7, 14, and 28 d. The resistivity data provides insights into the initiation and progression of cracks in concrete, with the gradual increase in resistivity serving as an indicator of impending failure in SFRC. The strength and wave velocity of SFRC are higher than that of NC, and the strength and wave velocity of concrete increase with age.

Matching Mechanism Between Grouting Material and Lightweight Aggregate in Preplaced Lightweight Aggregate Concrete

WANG Yingxiang, PENG Bo, WANG Jiantao, LIU Yunpeng

2024, 43(7):  2479-2489. 

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In this paper, lightweight and high strength grouting materials with different strength grades(60,75,90,100,110,120 MPa) were prepared. By compounding with different types and strengths of lightweight aggregate (high strength spherical fly ash ceramsite, low strength spherical fly ash ceramsite, gravel-shaped shale ceramsite), the matching mechanism between grouting material and lightweight aggregate in preplaced lightweight aggregate concrete was studied. The results show that there is a piecewise linear relationship between the strength of preplaced lightweight aggregate concrete and grouting material strength, and the slope of fitting curve can approximately reflect the utilization efficiency of the strength of grouting material. With the increase of the strength grade of grouting material, the utilization rate of concrete to the strength of grouting material decreases. The compressive strength and grain shape of aggregate also affect the utilization rate of the strength of grouting material. Due to the interlocking effect, the strength of lightweight aggregate concrete prepared by gravel-shaped shale ceramsite is significantly higher than that of concrete prepared by spherical fly ash aggregate with similar compressive strength. Two types of preplaced lightweight aggregate concrete with compressive strength of 81.2 MPa, dry apparent density of 1 735 kg/m³ and compressive strength of 68.2 MPa, dry apparent density of 1 520 kg/m³ were prepared by using high strength spherical fly ash ceramsite and gravel-shaped ceramsite, respectively.

Morphology Characteristics and Distribution Patterns of Slurry-Modified Recycled Aggregate Evaluated by Machine Learning

ZHANG Jiahao, CHEN Zhengfa, SONG Yan, CHEN Zhaoyan

2024, 43(7):  2490-2502. 

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The defects such as high water absorption, high pressure crushing value, surface microcracks and irregular morphology of recycled aggregate (RA) limit its recycling and utilization. The shell film structure formed on the surface of slurry-modified recycled aggregate (SRA) not only improves the mechanical properties of RA, but also has a significant impact on morphological characteristics of RA. In order to evaluate the effect of slurry-modified on morphological characteristics of RA, this study used fly ash based polymer slurry to modify recycled concrete aggregates (RCA) and recycled brick aggregates (RBA), and obtained and established datasets of morphological characteristics of RCA and RBA before and after slurry-modified using image processing technology. In addition, the article also combined machine learning techniques to extract key information from the dataset, thereby quantifying the morphological features of RA. After quantitative analysis, it is found that compared with before modification, the distribution range of axial coefficient, angularity, and sphericity of modified RA has been improved to varying degrees. Among them, slurry-modification has the most significant effect on improving angularity. The maximum improvement amplitude of slurry-modified recycled concrete aggregate (SRCA) is 132.2%, and the maximum improvement amplitude of slurry-modified recycled brick aggregate (SRBA) is 69.2%.

Solid Waste and Eco-Materials

Research Progress on Chloride Ion Penetration Resistance of Geopolymer Concrete

YU Jinhu, LI Qiang, LIU Xueying, ZHOU Shuguang, WANG Chao

2024, 43(7):  2503-2513. 

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Geopolymer concrete is a new type of green building material, and chloride ion transport is a key factor affecting its service life. Based on the introduction of the chloride ion transport mechanism of geopolymer concrete, this paper summarizes the characteristics and limitations of the test methods for the chloride ion permeability resistance of geopolymer concrete, introduces the interfering factors of the chloride ion permeability resistance of geopolymer concrete, and compares the chloride ion transport mechanism of ordinary concrete and geopolymer concrete. The article concludes by pointing out that the chloride transport model of geopolymer concrete under the influence of single factors such as high temperature, freeze-thaw, and etc., the influence of alkali admixture and water glass modulus on the resistance of geopolymer concrete to chloride infiltration, as well as the accuracy of the color rendering boundary concentration of chloride ions are still to be further investigated in depth.

Preparation of Single Phase Y Zeolite from Coal Gasification Slag

LYU Junmin, WANG Zheng, YANG Yingzhen, ZHAO Xiaoxia, FAN Subing

2024, 43(7):  2514-2521. 

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Coal gasification slag is a solid waste of coal chemical industry. Because it contains a lot of silicon and aluminum elements, it can be used as raw material to synthesize high value Y zeolite material, which realizes resource utilization. Y zeolite with octahedral morphology and single phase was successfully synthesized from Ningxia Ningdong coal gasification slag by hydrothermal synthesis method induced by directing agent after acid and alkali pretreatment. The effects of acid and alkali pretreatment conditions, Si/Al ratio, H₂O/SiO₂ ratio, crystallization temperature, crystallization time and directing agent content on the crystal phase of Y zeolite synthesized from coal gasification slag were investigated in detail. XRD, XRF, SEM and FT-IR were used to analyze the properties of synthesized Y zeolite. By optimizing the process conditions, the H₂O/SiO₂ ratio is reduced to 20, the crystallization time is shortened to 24 h, and the Y zeolite product has good crystallinity, high specific surface area of 538 m²/g and total pore volume of 0.350 cm³/g.

Solid Waste and Eco-Materials

Preparation of Coal Fly Ash-Based Zeolite X and Its Adsorption Application for O-Xylene, CO₂, and H₂

YANG Lele, LIU Zhiyuan, ZHANG Yalong, ZHANG Xiaoming, CHENG Xingxing

2024, 43(7):  2522-2529. 

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The optimal conditions for activating coal fly ash (400 ℃, m(NaOH)∶m(coal fly ash)=1∶2) were obtained by exploring the alkali fusion activation conditions, and the coal fly ash-based zeolite X with the highest relative crystallinity was obtained by hydrothermal synthesis at 80 ℃ for 18 h. The physical characteristics of synthesized zeolite X were characterized by XRD, FT-IR, SEM, and BET. The results show that the synthesized zeolite obtains a relatively specific surface area of up to 315.6 m²/g, an average pore diameter of 8.53 nm, and a total pore volume of 0.412 cm³/g. Coal fly ash-based zeolite X also shows higher adsorption capacity of o-xylene, carbon dioxide and hydrogen, which are 75.20 mg/g, 2.45 mmol/g, and 0.22%(mass fraction), respectively. The adsorption behavior can be well fitted by Langmuir adsorption isotherm, which belongs to monolayer adsorption. This study reduces the energy consumption in the zeolite process of coal fly ash, and the prepared coal fly ash-based zeolite X has potential commercial value in energy and environmental protection.

Composition Design and Application of CFB Ash-Slag Concrete

LI Weihong, GUO Wenbin, GUO Xiangbing, CHEN Xiao, ZHOU Mingkai

2024, 43(7):  2530-2538. 

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With the large-scale application of clean combustion technology of circulation fluidized bed (CFB) boiler, the disposal CFB ash-slag has become an urgent problem to solve. CFB ash-slag concrete was prepared by using crushed stone as coarse aggregate, CFB slag as fine aggregate and CFB ash as mineral admixture. The effects of CFB slag sand rate and CFB ash content on workability and mechanical properties of CFB ash-slag concrete were discussed, and the mix proportion of CFB ash-slag concrete was optimized. The Cl^- permeability resistance, freeze resistance and dry shrinkage of CFB ash-slag concrete and machine-made sand concrete were compared. The results show that compressive strength of CFB ash-slag concrete first increases and then decreases with the increase of CFB slag sand rate. With the increase of CFB ash content, the slump of CFB ash-slag concrete gradually decreases, and the compressive strength first increases and then decreases. The optimal mix proportion is cement 280 kg/m³, CFB ash 120 kg/m³, mineral powder 40 kg/m³, CFB slag 620 kg/m³, gravel 1 013 kg/m³, water 223 kg/m³, water reducing agent 8.8 kg/m³. Compared with machine-made sand concrete, CFB ash-slag concrete has better Cl^- permeability resistance, freeze resistance and less drying shrinkage, and the small precast components prepared by CFB ash-slag concrete have better application effects in practical engineering.

Preparation and Microanalysis of Geopolymer Low-Strength Grouting Material Based on Self-Combusting Gangue

WU Qiugang, ZHAO Heng, LIU Wei, WANG Xinfu, WANG Yanjun, HE Jianguo, ZHANG Mei, ZHU Bei

2024, 43(7):  2539-2547. 

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With self-combusting gangue as raw material, fly ash and low dosage of composite Portland cement P·C 42.5 as supplementary materials, geopolymer low-strength grouting materials based on self-combusting gangue were prepared by the excitation of calcium carbide slag, and the samples were microscopically analyzed. The experimental results show that when the amount of calcium carbide slag mixing (9.65%, mass fraction) is the same, the compressive strength development of samples is more favorable when the mass ratio of gangue, fly ash and cement is set to 5∶3∶2 or 5∶2∶3, the geopolymerization of the sample system is higher and the compressive strength (55 d) increases by 70%~86% compared to the samples with mass ratio of 7∶2∶1 and 7∶1∶2. At the same time, compared with the samples without adding desulfurization gypsum, adding 20% (mass fraction) desulfurization gypsum greatly improves the compressive strength of samples during the whole process of curing, and the compressive strength (55 d) increases by 21%~50%. The combination of correlation, XRD, SEM and FTIR analyses indicate that the main hydration products of samples are ettringite, C-S-H gel, C-A-S-H amorphous gel and others, and the compressive strength of samples is mainly derived from the C-A-S-H amorphous gels produced by geopolymerization.

Mixture Ratio of Lithium Slag-Based Controllable Low Strength Materials Based on Orthogonal Experiment

LIU Rui, LIU Ze, ZHAO Lijie, ZHANG Shuai, WANG Dongmin

2024, 43(7):  2548-2555. 

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In this paper, controlled low strength material (CLSM) was prepared from lithium slag. Based on the single factor test, the effects of cement content, water-binder ratio and water-reducing agent content on flexural strength, compressive strength, fluidity and bleeding rate of lithium slag-based CLSM were investigated by orthogonal test. The results show that the water-binder ratio and the amount of superplasticizer have significant effects on fluidity and bleeding rate of the materials. In CLSM system with large amount of lithium slag, the cement content has little effect on the bleeding rate, and increasing the cement content would increase the compressive strength and flexural strength of CLSM. Comparing the influence of various factors on CLSM, the suitable mix ratio to meet the requirements of CLSM performance index is as follows: cement content 12% (mass fraction, same below), lithium slag content 88%, water-binder ratio 0.57, water reducer content 0.20%. At this time, the fluidity of CLSM is 231 mm, the bleeding rate is 1.49, the 28 d flexural strength can reach 1.74 MPa, and the 28 d compressive strength is 4.90 MPa. All indicators are excellent.

Experimental Study on New Composite Excited Lithium Slag-Based Curing Agent for Reinforcing Soft Soil

YANG Lin, YANG Jianyu, YANG Weijun

2024, 43(7):  2556-2564. 

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In order to improve the utilization rate of solid waste lithium slag, lithium slag was used as raw material, quick lime was selected as external additive, and calcium carbonate and sodium hydroxide were added as composite activators. A new type of soft soil curing agent material was developed by alkali excitation technology. The curing mix ratio of new composite excited lithium slag-based curing agent (CELS) was studied by orthogonal test, and the influences of various factors on the compressive strength of solidified soil were explored. At the same time, combined with XRD and SEM, the curing mechanism and microstructure evolution between curing agent and soft soil were revealed. The results show that the optimum mixture ratio of curing agent is 73% (mass fraction) of lithium slag, 18% (mass fraction) of lime, 9% (mass fraction) of composite activator, and the mass ratio of calcium carbonate to sodium hydroxide is 1∶1. Under this mix ratio, the unconfined compressive strength of solidified soil at 7 and 28 d is 1.32 and 2.35 MPa, respectively, and the water stability coefficient is 0.80 and 0.87, respectively. Under the synergistic effect of quicklime and composite activator, the cementitious materials such as calcium aluminosilicate hydrate (C-A-S-H) and sodium aluminosilicate hydrate (N-A-S-H) in solidified soil increase significantly, and the density of soil structure increases, thereby improving the strength and water stability of solidified soil.

Adhesion Property of Mortar Prepared by Granite Tailing Sand

HE Juan, LIU Shuang, SONG Xuefeng, XU Shanhansu, LI Mengmeng

2024, 43(7):  2565-2576. 

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Granite tailing sand (GTS) was used to prepare mortar. The influences of binder-sand ratio, polyvinyl alcohol latex powder (PVAP) and polyvinyl alcohol fiber (PVAF) on the adhesion property of mortar were studied. The relationship between mortar failure mode and tensile adhesion strength was analyzed, and its micro-mechanism was studied by SEM. The results show that the adhesion property of the mortar is improved by single-doped with PVAP or PVAF, and be optimal when PVAP and PVAF are mixed-doped. When the binder-sand ratio for mortar is 1∶2, PVAP is 0.9% (mass fraction) and PVAF is 1.5% (volume fraction), the adhesion property of mortar is optimal, and the 28 d tensile adhesion strength is up to 1.75 MPa. The failure mode of mortar is affected by the tensile adhesion strength. The failure mode is mostly interfacial failure when PVAP and PVAF are not added. The failure mode is mostly matrix failure when PVAP and PVAF are mixed-doped. The failure mode is mostly interface-matrix failure when PVAP or PVAF is single-doped.

Effect of Mechanical Activation on Early-Age Performance of Sodium Carbonate-Activated GBFS Binders

HU Kaiwei, CHEN Xuan, LI Tingfeng, ZHANG Junjie, GAO Xuan, YANG Tao

2024, 43(7):  2577-2583. 

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In response to the problem of long setting time and slow early strength development of sodium carbonate-activated ground blast furnace slag (GBFS) binders, the mechanical activation was adoptd to treat granulated blast furnace slag for accelerating the alkali-activation process. The effect of mechanical activation on the setting time, strength development, reaction kinetics and phase evolution of binders were investigated. The results show that mechanical activation can accelerate the dissolution and release of Ca²⁺, SiO₄ and AlO^-₄ in slag to promote the formation of calcium carboaluminate mineralogical phases. Accelerated dissolution of Ca²⁺ is beneficial for consuming CO^2-₃ in the liquid phase, and the initial and final setting time of binders decreases from 23.6 and 30.5 h to 2.3 and 3.2 h, respectively. At the same time, the induction period of alkali-activation is shortened using mechanical activation, the degree of alkali-activation is effectively improved, and the total heat release within 96 h increases from 41.30 J/g to 55.47 J/g. The formation of calcium aluminosilicate hydrate gel phase is promoted, which densifies the pore structure, reduces the total porosity from 30.49% to 27.01%, and reduces the macro-capillary porosity from 17.69% to 2.32%. The 28 d compressive strength of binders achieves 36.58 MPa, which increases to 230% compared with the reference sample.

Effects of Silica Fume and GGBS on Mechanical Properties of High Volume Fly Ash Mortar and Its Mechanism

LIU Yang, WANG Jiali, LUO Dong, YUAN Heping, LU Naiwei, WANG Bowen

2024, 43(7):  2584-2594. 

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Using silica fume and ground granulated blast furnace slag (GGBS) as auxiliary cementitious materials and polyhydroxylic acid high-performance water reducer, the effects of silica fume and GGBS on the compressive strength of high volume fly ash mortar were studied. The pore structure, microstructure, and phase composition of prepared specimens were analyzed by mercury intrusion test (MIP), scanning electron microscope (SEM) and X-ray diffraction (XRD), and the mechanism of the effect of silica fume and GGBS on the strength of high volume fly ash mortar was obtained. The results show that with the increase of silica fume content, the compressive strength of high volume fly ash mortar mixed with silica fume increases first and then decreases. The law of GGBS mixing is similar to that of silica fume. Whether it is mixed alone or mixed, silica fume and GGBS are mixed together, the strength of mortar is improved compared with other age groups, and they show good synergy. Both silica fume and GGBS can improve the strength of high volume fly ash mortar. The total porosity and proportion of macropores of mortar specimens are negatively correlated with compressive strength. The higher the strength of mortar specimens is, the denser the microstructure is. But compared with the total porosity, the proportion of pores and macropores shows a better correlation with compressive strength. When the mass fraction of silica fume and GGBS is 8% and 6% respectively, the strength of mortar at 28 d is the highest, which is 88.05 MPa.

Preparation of New Lightweight Ceramic Bricks Based on Silt and Carbide Slag

CAO Dan, SHEN Ding, YAO Shunyu, DING Zhiyao, HUANG Ziyu, LI Mengqi, HUANG Muyang, BAO Shenxu

2024, 43(7):  2595-2601. 

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In order to realize the efficient resource utilization of silt and carbide slag, the optimal process for preparing lightweight ceramic bricks was explored by using silt and carbide slag as the main raw materials and compressive strength as the main index. The effects of raw material mix ratio, calcination temperature and holding time on the compressive strength of lightweight ceramic bricks were discussed by single factor experiment, and the optimum experimental conditions were obtained. The reaction process and mechanism of preparing lightweight ceramic bricks were studied by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that when the content of silt is 90%(mass fraction), the content of carbide slag is 10% (mass fraction), the calcination temperature is 1 100 ℃, the holding time is 40 min, and the heating rate is 4 ℃/min, the prepared lightweight ceramic bricks have the best performance. The compressive strength can reach 25.94 MPa, while taking into account the low density characteristics of lightweight ceramic bricks. Halloysite is converted into quartz during the heating process. Quartz can promote the raw material to become liquid phase under high temperature conditions, which is the reason why the product is densified. This study provides a new idea for the comprehensive utilization of two kinds of bulk solid waste, which is beneficial to reduce the harm of solid waste storage to the environment and the dependence on natural resources in the preparation process of traditional ceramic bricks.

Solid Waste and Eco-Materials

Experimental Study on Road Performance of Weak Alkali-Activated Phosphorus Slag-Cement Composite Filler

YIN Yuan, LIN Kang, ZENG Weixin, CHENG Shufan

2024, 43(7):  2602-2611. 

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Taking solidified phosphorus slag as filler for roadbed or pavement base is an effective way to utilize solid waste resources, which has wildly economic benefits and social value. In this paper, the road performance of phosphorus slag-cement composite filler was analyzed in terms of strength and water durability through laboratory and on-site tests. Then, the availability of the solidification method was discussed through specific engineering cases. The test results indicate that under weak alkali activation (pH=8.0), the compacted phosphorus slag mixture can form a solidified body, whose strength could meet the requirements of roadbed filler. However, strength incensement of solidified body is relatively slow. The compressive strength of solidified body after 7 d is about 50% of the compressive strength after 28 d. The solidified phosphorus slag-cement composite filler is water resistance. Once the cement clinker content is greater than 7% (mass fraction), the damage that affects the integrity of the sample cannot be observed during a 60 dfree soaking, and the softening coefficient of the solidified sample decreases as the content of cement increases. Moreover, keeping the strength as a constant, using curing agent (Na₂SiO₃) can save the amount of cement used and improve the economic efficiency of solidification method. Excessive alkali activation (pH=10.0) can only improve the early strength of solidified body and has little effect on the 28 d strength. Finally, the on-site engineering practice shows that the weak alkali-activated phosphorus slag solidification method can effectively reuse of phosphorus slag resource, which has strong generalizability in highway roadbed and pavement base filling engineering.

Effect of Soluble Phosphorus on Core Strength and Paper Core Bonding Property of Paper-Based Gypsum Board

LI Yi, WANG Hongxia, WU Fade, YU Jian, YU Haiyan, GAO Chunyong, GUO Junhua, GAO Ruijun

2024, 43(7):  2612-2619. 

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In order to improve the efficient resource utilization of phosphogypsum in paper-based gypsum board, the effect of soluble phosphorus, naphthalene water reducer (FDN) and modified starch (MS) on the performance of plasterboard were studied by X-ray diffraction, microcalorimetry and scanning electron microscopy. The results show that in the presence of FDN, soluble phosphorus will aggravate the retarding effect on hemihydrate gypsum and slightly reduce the adverse effect on the strength of gypsum samples. MS significantly shortens the hydration process of gypsum and reduces the strength of gypsum samples. Under the coexistence of MS and FDN, with the increase of soluble phosphorus content, the time for gypsum to reach the highest exothermic peak is prolonged, the peak value of hydration heat release and the total amount of hydration heat release in 2 h are decreased. 0.50% (mass fraction, same below) soluble phosphorus can offset part of the promoting effect of MS on gypsum, and greatly reduce the strength of gypsum samples. In the presence of FDN, soluble phosphorus significantly reduces the aspect ratio of hydration products, the crystal morphology is irregular short column or block, and the crystal contact points are less. When FDN and soluble phosphorus coexist, MS causes the hydration products to appear small blocks and coarse plates. Under the dosage of 0.4% FDN and 0.2% MS, over 0.50% soluble phosphorus will have a more adverse effect on the paper-based gypsum board. In this research, in order to ensure the paper core bonding performance of grade I, the soluble phosphorus content should not exceed 0.25%.

Solid Waste and Eco-Materials

Low-Carbon Preparation of Ceramic Tiles from Building Ceramic Solid Waste by Simulating Hydrothermal Alternation

WU Wenxin, ZHOU Zhengyuan, XIA Guanghua, NING Gaopeng, ZHOU Cailing

2024, 43(7):  2620-2629. 

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Ceramics are usually sintered over 1 000 ℃, which leads to 60% energy consumption of ceramic production process. Low temperature sintering is a key factor for energy saving and carbon reduction of ceramic industry.This article proposes a low-carbon method for preparing ceramics by simulating hydrothermal alteration reaction at 200 ℃ using ceramic solid waste as raw material. Waste ceramics were firstly pre-treated by ball milling to obtain submicron powder. Ceramic tiles were prepared from ceramic powder by hydrothermal alteration simulation. Under the optimal condition of 6 h ball milling of ceramic waste solid, 25% water content of submicron powder, K₂SiO₃ solution and 36 h reaction at 200 ℃, the flexural strength of the final product can reach (32.1±4) MPa fitting application requirement of ceramic tiles. X-ray diffraction, Fourier infrared spectroscopy and scanning electron microscopy were used to characterize the physical phase composition, functional group structure, and microscopic morphology of the samples before and after the reaction, and a possible reaction mechanism was given. It is confirmed that orthoclase and α-quartz crystals are produced during the hydrothermal etching reaction, and the growth of these two crystals effectively improves the flexural strength of ceramic tiles.

Strength Characteristics and Micro Mechanism of Straw-Polyvinyl Alcohol Reinforced Silty Clay under Dry-Wet Cycle

WANG Jindong, LUO Mengting, LU Qingrui, WANG Qiuzhe, LI Dongwei

2024, 43(7):  2630-2639. 

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Curing agent is often used to enhance the mechanical properties of soil when clay sites are encountered in engineering construction. In this paper, the mechanical properties of silty clay reinforced by straw-polyvinyl alcohol (0%, 0.5%, 2.0%, 3.0%, 4.5%, mass fraction) under dry-wet cycle were studied. The microscopic analysis was carried out by means of electron microscope scanning test and IPP software. The results show that when the concentration of polyvinyl alcohol is 2%, the polyvinyl alcohol (PVA) solution fills the pores, wraps the soil particles, and the mechanical properties of soil are the best under different dry-wet cycles.

Effect of Graphene Oxide on Hydration and Mchanical Properties of Natural Hydraulic Lime

ZHANG Biao, LIU Hongyu, QI Nan, WANG Fen, ZHU Jianfeng, LI Li, MA Tao, LUO Hongjie, SHI Pei

2024, 43(7):  2640-2648. 

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The stone cultural relics are important cultural heritage, however, fissures can lead to destabilization, water seepage and weathering diseases. Therefore, it is of great significance to develop a suitable grouting material for repairing fissures in stone cultural relics. The grouting material was prepared by adding graphene oxide (GO) into natural hydraulic lime (NHL2). The influence of GO content on hydration process and products of NHL2 was studied using SEM, TG, XRD and FT-IR. The feasibility of this material for grouting reinforcement of stone cultural relics was evaluated by mechanical properties and simulated grouting tests. The results indicate that the addition of GO can accelerate hydration process and promote formation of regular and dense flower-like aggregated hydration products. When GO content is 0.05% (mass fraction), the sample has the highest content of hydration products and the best mechanical properties. The compressive strength and flexural strength of samples cured for 28 d can reach 2.83 and 1.63 MPa, which increases by 19.91% and 23.40% with the blank sample, respectively. Furthermore, there is excellent bonding strength between grouting material and sandstone, the interface of the two is closely combined with good compatibility. This work provides reference for grouting reinforcement of fissures in stone cultural relics.

Ceramics

Research Status on Influencing Factors of High Thermal Conductivity Si₃N₄ Ceramic Substrate

ZHU Yunrui, HE Yunpeng, YANG Jian, ZHOU Guoxiang, LIN Kunpeng, ZHANG Yanzhao, YANG Zhihua, JIA Dechang, ZHOU Yu

2024, 43(7):  2649-2660. 

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The high degree integration of electronic power technology has put forward higher requirements for heat dissipation and strength of brittle ceramic substrates carrying electronic components. Due to its excellent intrinsic thermal conductivity and mechanical properties, silicon nitride ceramics have broad development prospects in the field of high-power semiconductor device packaging. However, the thermal conductivity of Si₃N₄ that can be achieved in commercial and experimental studies is much lower than its intrinsic thermal conductivity, and how to improve the thermal conductivity of Si₃N₄ on the basis of ensuring its excellent mechanical properties is still a difficult problem. In this paper, the recent development of high thermal conductivity silicon nitride is summarized, and the influencing factors and improvement methods of the actual thermal conductivity of Si₃N₄ are emphatically discussed. At the same time, the advantages and disadvantages of several Si₃N₄ sintering processes are compared, and make a brief introduction of the current mainstream commercial Si₃N₄ ceramic substrate molding process. The development direction of Si₃N₄ ceramic substrate is prospected finally.

Research Progress of Additive Manufacturing SiC Ceramic Mirror

LI Wei, ZHANG Ge, CUI Congcong, BAO Jianxun, GUO Conghui

2024, 43(7):  2661-2671. 

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SiC ceramics have excellent mechanical properties and good thermal properties, and are one of the ideal materials for preparing space optical mirrors. SiC ceramic mirrors prepared by traditional forming technology generally have problems such as low light weight and long preparation cycle, which are difficult to meet the development needs of space optical systems. At present, additive manufacturing technology shows its great potential in the preparation of ultra-lightweight mirrors with low cost and short cycle. In this paper, the material properties of common mirrors are compared firstly. Then, the research progress of additive manufacturing technology for SiC ceramic mirrors is reviewed. The component design, preparation process and densification method of SiC ceramic mirrors preparation process are discussed in detail, and the technical route of SiC ceramic mirrors prepared by additive manufacturing technology is summarized. Finally, the future development of additive manufacturing technology for SiC ceramic mirrors is prospected.

Refractory Materials

Effect of Raw Material Composition on Microstructures and Properties of Microporous Periclase-Composite Spinel (Mg(Fe, Al)₂O₄) Ceramics

CHEN Qianlin, YAN Wen, WANG Xiao, LI Yawei

2024, 43(7):  2672-2679. 

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In the work, microporous periclase-composite spinel (Mg(Fe, Al)₂O₄) ceramics was successfully prepared using calcined MgO, Fe₂O₃ and Al(OH)₃ as raw materials by in-situ decomposition synthesis. Meanwhile, the effects of raw material on its microstructures and properties were studied. The results show that when the periclase-composite spinel (Mg(Fe, Al)₂O₄) content is 0% (mass fraction, the same below), less neck connection form in the sample as well as the compressive strength is low. When the theoretical periclase-composite spinel (Mg(Fe, Al)₂O₄) content is 4%~16%, the content of the liquid increases and the mass transport accelerates. Then, lots of neck connections form and the compressive strength is high. When the theoretical periclase-composite spinel (Mg(Fe, Al)₂O₄) content is 24%, the expansion amounts caused by the formation of composite spinel increase so the inter-particle pore size increases and the neck connections decrease. Therefore, the compressive strength of the sample decreases. When the theoretical periclase-composite spinel (Mg(Fe, Al)₂O₄) content is 12%~16%, microporous periclase-composite spinel (Mg(Fe, Al)₂O₄) ceramics has excellent comprehensive properties, the apparent porosity of 22.3%~24.6%, the bulk density of 2.75~2.80 g/cm³, the compressive strength of 100.6~123.1 MPa.

Preparation of Si₂N₂O/SiC Composite Powders Using Carbothermal Reduction Nitridation Method for Diatomite

WAN Gan, KUANG Meng, HUANG Siyuan, ZHANG Jinjun, WANG Ping, ZHANG Shengzhou

2024, 43(7):  2680-2684. 

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Silicon oxynitride (Si₂N₂O) is a high-performance refractory and high-temperature structural material, which has advantages such as excellent creep resistance, corrosion resistance, and oxidation resistance. In this work, diatomite was used as silicon source, acetylene carbon black was used as reducing agent, and the Si₂N₂O/SiC composite powders were synthesized in situ on the surface of diatomite through carbothermal reduction nitridation method. The samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and N₂ adsorption/desorption isotherms. The results indicate that under the condition of raw materials ratio m(diatomite)∶m(acetylene carbon black)=1∶1, the SiO₂ completely transforms into Si₂N₂O and β-SiC after calcination at 1 450 ℃ for 4 h, and the sample shows a spherical morphology with mesoporous structure, while a large number of layered small particles distribute around the large particles. As a high-performance high-temperature structural material, Si₂N₂O/SiC composite powders could be a promising candidate for application in the field of structural composite materials.

New Functional Materials

Preparation and Electrochemical Properties of Novel Cement-Based Batteries

XIA Donglin, WANG Yajie, JIANG Yang

2024, 43(7):  2685-2696. 

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As a kind of building energy storage device, the novel cement-based battery has the advantages of low cost, environmental friendliness and rechargeability, and has been widely concerned by researchers at home and abroad. In this study, the electrode of a new cement-based rechargeable battery was made by mixing different conductive fillers with positive and negative active substances and grinding, and then drying by vacuum. And the effects of the kinds and content of the conductive fillers on the electrochemical property of the rechargeable cement-based batteries were investigated. The results show the cement-based battery with the mass fraction of 25% carbon black possesses a battery capacity of 12.5 mAh, an energy density of 1.575 Wh/m², and the discharge lifespan exceeds 3.3 h, its electrochemical properties are better than that of graphite cement-based batteries and graphene cement-based batteries with the same mass fraction.

Preparation and Mechanism of AgCl/Ag Composite Powder Material

YANG Huajian, ZHAO Yuanyun

2024, 43(7):  2697-2705. 

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AgCl powder materials with different morphologies were prepared by ultrasound-assisted dealloying method using Ca-Mg-Cu-Ag amorphous strips as precursors, Cu-Ag nanoporous material as intermediate product, and hydrochloric acid solutions with different solvent compositions as reaction solution. The morphology, structure, and composition of samples were characterized and analyzed using SEM, XRD and other detection methods, and the formation process and mechanism of AgCl/Ag composite powder material were revealed in different reaction solutions. The results show that under ultrasound-assisted, when using hydrochloric acid ethanol solution as reaction solution, Cu-Ag nanoporous material can be completely dissolved in the solution and then different morphologies of AgCl powder material can be reprecipitated form the same solution after changing the volume ratio of concentrated hydrochloric acid solution to ethanol solvent.When using hydrochloric acid aqueous solution as reaction solution, Cu-Ag nanoporous material can only directly transform into nearly spherical AgCl powder material after changing the volume ratio of hydrochloric acid aqueous solution to distilled water solution, which cannot be dissolved in hydrochloric acid aqueous solution first and then reprecipitated form the same solution. With the coexistance of ultrasound treatment and hydrochloric acid ethanol solution for the Cu-Ag nanoporous material, there exists a novel AgCl ‘formation-dissolution-precipitation’ mechanism, which can be used to accurately control the morphology, structure, and size of the reprecipitated AgCl powder material.