Table of Content

15 March 2024, Volume 43 Issue 3

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Cement and Concrete

Comparative Study on Performance of Two Water Resistant Long Afterglow Materials for Preparing Luminescent Concrete

LYU Yajun, SONG Caihong, DANG Juntao, DONG Binbin, QIAO Min, ZHANG Kangjie, MA Xiaofeng

2024, 43(3):  781-792. 

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The hydrolytic instability of fluorescent powder can diminish luminescent concrete's mechanical strength and luminescent performance. This study used two methods, SiO₂ coating and hydrophobic treatment, to treat long afterglow fluorescent powder with water resistance and prepare luminescent concrete. The compressive strength, luminescent performance and microstructure of luminescent concrete prepared by adding fluorescent powder with different water resistance treatments were tested to reveal the mechanism of improving the performance of luminescent concrete by fluorescent powder. The results show that, compared to the SiO₂ encapsulation method, the hydrophobic treatment of fluorescent powder achieves superior water resistance performance. And the 28 d compressive strength of hydrophobic treated fluorescent powder luminescent concrete has increased by 8.0%~25.7%, with a maximum strength of 80.2 MPa and an optimal dosage of 5%~10% (mass fraction). Excessive addition will have adverse effects. Compared with the luminescent concrete without water-resistant fluorescent powder, the microstructure density, compressive strength and luminescent performance of the two types of water-resistant fluorescent powder luminescent concrete are significantly improved.

Effects of Triethanolamine and Zinc Stearate on Properties of Foam Concrete

LI Zhaorui, WANG Zhenjun, ZHANG Haibao, ZHANG Yaming, ZHANG Songlin, ZHANG Bolun

2024, 43(3):  793-805. 

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In order to solve the long-standing problem of high water absorption of foam concrete, the effects of triethanolamine (TEA) and zinc stearate (ZS)on the pore characteristic, mechanical property and waterproof performance of foam concrete were studied. And the modification mechanism of TEA and ZS on foam concrete was studied by contact angle test, scanning electron microscopy with energy spectroscopy and X-ray diffractometer test methods. The results show that the addition of 1.6% (mass fraction) TEA and 0.4% (mass fraction) ZS can increase the proportion of pores with a diameter of less than 500 μm, and increase 28 d compressive strength of foam concrete to 1.66 MPa. The addition of 0.4% (mass fraction) TEA and 1.6% (mass fraction) ZS can reduce the water absorption of foam concrete to 2.8%, 7.9% and 10.5% at 1, 2, 3 d, and the contact angle reaches up to 134.9°, so that the foam concrete has a hydrophobic surface. The co-doping of TEA and ZS can enhance the stability of foam in the solidified cement slurry, refine the pore structure, reduce the number of connecting pores and improve the mechanical property and waterproof performance of foam concrete.

Mechanical Properties and Energy Evolution of Cellulose-Basalt Hybrid Fiber Sprayed Concrete

LIU Fuqiang, MA Qinyong

2024, 43(3):  806-815. 

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In order to study the effect of cellulose fiber and basalt fiber content on the mechanical properties of sprayed concrete, work performance and mechanical performance tests were conducted on sprayed concrete with different fiber content. Based on the energy evolution curve, the energy changes at different stages of sprayed concrete were compared and analyzed, and the toughening and crack resistance mechanism of fibers on sprayed concrete was analyzed by combining macroscopic experiment and SEM. The results show that the addition of cellulose fiber and basalt fiber can lead to a decrease in the slump of sprayed concrete. The compressive strength and splitting tensile strength of sprayed concrete increase first and then decrease with the increase of the content of two fibers. Under the load action, the energy evolution curve of sprayed concrete mainly goes through four stages: initial damage stage, linear elastic stage, mutation damage stage and destruction stage. The incorporation of appropriate amount of cellulose fiber and basalt fiber enhances the crack resistance and energy consumption capacity of sprayed concrete. After adding cellulose fiber, the particle distribution of hydration products in the interface transition zone of sprayed concrete becomes more uniform, and the interface structure becomes smoother and denser. The friction between fibers and matrix provides the energy required for crack propagation, enhancing the ductility and crack resistance of sprayed concrete.

Durability Deterioration Law of Basalt Fiber Concrete under Early Salt-Freezing Coupling Effect

XU Cundong, LI Bofei, LI Zhun, WANG Hairuo, CAO Jun, XU Hui

2024, 43(3):  816-824. 

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To address the problem of rapid durability degradation of early freezing plain concrete in the cold and arid regions of northwest China under the action of salt-freezing coupling effect, based on the indoor rapid freezing and thawing test, the durability deterioration law of concrete with different volume content of basalt fibers was studied using a 3.5% (mass fraction, the same below) NaCl+5.0% Na₂SO₄ composite salt solution as a freeze-thaw medium, and scanning electron microscope, ultrasonic defect detection and nuclear magnetic resonance pore size detection were applied to explore the improvement effect of basalt fibers on the macroscopic properties of concrete under the salt-freezing coupling effect at the micro level. The results show that the addition of basalt fibers in the early freezing plain concrete can effectively improve the compressive strength and reduce the mass loss. With the increase of fiber content, the compressive strength and relative dynamic elastic modulus increase first and then decrease. With the increase of freeze-thaw cycle time, the ultrasonic pulse propagation velocity of different volume content of basalt fibers in the early freezing plain concrete gradually increases, and the total porosity of each group specimens is positively correlated with the freeze-thaw cycle time, and the addition of basalt fibers increases the proportion of harmless pores, reduces the proportion of multi-harmful pores, and improves the durability resistance of concrete. In the tests, the fiber of 0.15% (volume fraction) group of test blocks has the most superior performance among all of test blocks. The research results can provide a reference for the study of durability of early freezing plain concrete in cold and arid irrigation areas and later maintenance.

Experimental Study on High Temperature Performance of Hybrid Fiber Reinforced Ultra-High Performance Concrete

LUO Yiming, ZHANG Bo, LIU Yanyu, WU Shoujun, FU Guo

2024, 43(3):  825-832. 

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In this work, the physical and mechanical properties of hybrid steel fiber (SF)-polypropylene fiber (PPF)-calcium sulfate whisker (CSW) reinforced ultra-high performance concrete (UHPC) were investigated before and after exposed to 200~800 ℃. The morphologies of hybrid SF-PPF-CSW reinforced UHPC were observed with optical microscope and scanning electron microscope, respectively. And the action mechanism of multi-scale fibers in the process of fracture development in matrix was discussed. The results show that with the increase of temperature, the mass loss of UHPC increases while the ultrasonic pulse velocity decreases. Meanwhile, the SF-PPF-CSW has a certain slowing effect on the decrease of ultrasonic pulse velocity of matrix. The hybrid SF-PPF-CSW reinforced UHPC shows slight change (<5%) in flexural strength below 400 ℃, while sharply decreases above 400 ℃. After exposure to 800 ℃, the residual flexural strength of UHPC is about 19.2%~24.7% of initial value. With the increase of temperature, the residual compressive strength increases first and then decreases. The residual compressive strength reaches the maximum value at 400 ℃, which is 48.9%~62.0% higher than that at normal temperature. The hybrid SF-PPF-CSW can effectively improve the physical and mechanical properties of UHPC at all of tested temperatures, and mechanical property enhancement is optimal with 1.7%(volume fraction) SF、0.3%(volume fraction) PPF and 1.0%(volume fraction) CSW.

Preparation and Performance of Sleeve Grouting Material Modified with Polymer Emulsion for Prefabricated Buildings

FU Wanwan, LAO Jiayue, GUO Keyu, CHEN Liuwei, WU Shifang, ZHOU Wei, TAN Xiaoming, PENG Hao

2024, 43(3):  833-843. 

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In this study, two kinds of polymer emulsion-modified sleeve grouting materials were prepared with vinyl acetate-ethylene copolymerization emulsion (EVA) and acrylate emulsion (PAE), respectively. The effects of polymer emulsion on the fluidity, compressive strength, water absorption, expansion rate, durability, tensile property and microstructure of the sleeve grouting material were investigated and its cost accounting was executed. The results show that polymer emulsion can significantly improve the fluidity, compressive strength, water absorption, sulfate resistance and freeze thaw resistance of grouting materials, and the comprehensive properties of PAE modified sleeve grouting materials are better than EVA modified ones. PAE modification enhances the overall cohesion and density of grouting material, ensuring that the expansion rate of the grouting material has little negative impact and no bleeding phenomenon. At the same time, it can enhance the tensile performance, tensile strength, and bonding strength of grouting material joint. When the PAE content is between 0.3% and 1.0% (mass fraction), the performance of PAE modified grouting material meets the corresponding national standard requirements, and the preparation cost is relatively low.

Effect of Ferrous Sulfate on Properties and Hydration Products of Aluminate Cement Paste

ZHANG Mengzhen, LOU Guanghui, LIU Zixian, CAI Jiwei, XU Gelong, QIAO Yijia, ZHANG Xiangfei

2024, 43(3):  844-850. 

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Iron phase has a significant positive effect on the durability of cement concrete. In order to broaden the sources of iron phase, the effects of iron salts on the properties and hydration products of aluminate cement were studied. The combination of aluminate cement and sulfate (gypsum and ferrous sulfate) was used to form ettringite as a main hydration product of aluminate cement. Then, the influence of the proportion of ferrous sulfate in sulfate on the setting time, compressive strength and volume stability of aluminate cement paste was studied. The type and microstructure of the hydration products were also analyzed by XRD and SEM to reveal the influence mechanism of ferrous sulfate on properties of cement paste. The results show that appropriate amount of sulfate can improve the compressive strength of aluminate cement paste. Ferrous sulfate has a slight promoting effect on the setting time and a significant inhibiting effect on the expansion rate of aluminate cement. Ferrous sulfate inhibits the formation of ettringite, and an appropriate amount of ferrous sulfate makes the generated ettringite with smaller size and uniform distribution, which is conducive to improving the compressive strength of the hardened paste.

High Temperature Performance of Blended Fiber Cement Mortar

GUO Zirong, YANG Dingyi, CAO Zhonglu, JIA Xiangfeng, ZHAO Jian, CHEN Longxiang, MAO Xiang

2024, 43(3):  851-865. 

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The high temperature caused by fire will cause serious damage to cement-based composites, and mixing basalt fiber can improve the high temperature resistance of cement-based composites to some extent. In order to study the performance changes of cement mortar mixed with different kinds of basalt fiber and polypropylene fiber after high temperature, the basic mechanical properties of blended fiber cement mortar after high temperature were tested, and the microstructure of blended fiber cement mortar was analyzed by means of scanning electron microscope (SEM) and mercury intrusion test. The results show that the mixture of different types of basalt fiber and polypropylene fiber can improve the high temperature resistance of cement mortar. When the temperature is 200 ℃, due to the secondary hydration in the cement mortar, the compressive strength and flexural strength of blended fiber cement mortar are significantly improved. As the temperature rises to 800 ℃, the internal structure of cement mortar is destroyed, the porosity gradually increases, and the mechanical properties gradually decline. However, the performance of blended fiber cement mortar is still higher than that of the reference group, because the polypropylene fiber leaves a large number of pores after melting at high temperature, alleviating the internal pore pressure of cement mortar, and the basalt fiber plays a bridging role in cement mortar, and the propagation of high temperature cracks is alleviated.

Thermal Performance Test and Numerical Simulation of Phase Change Thermostatic Wall Board

ZHANG Luman, HOU Feng

2024, 43(3):  866-877. 

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In order to address the spatial and temporal contradiction in wall energy supply and further enhance building comfort, phase change microcapsules (Micro-PCM) were incorporated into cementitious materials to develop a phase change mortar, leveraging the advantages of both phase change materials and cement. A layer of phase change mortar was applied onto the surface of a wallboard, which was subjected to simulated solar radiation using incandescent lamp heating. The thermal performance of the phase change thermostatic wall board under solar radiation was experimentally investigated, while numerical simulations were conducted using COMSOL software. The results demonstrate that with the increase of Micro-PCM content, the heat storage capacity of phase change thermostatic wall board increases. When the Micro-PCM content reaches 40% (volume fraction), compared to ordinary wallboards, there is a reduction in peak temperature by 5.166 ℃, delay in peak temperature time by 145 min, decrease in peak temperature amplitude by 4.509 ℃, and reduction in peak heat transfer by 22.202 W/m². Furthermore, when phase change mortar is placed within aerated concrete block walls, there is a decrease in peak temperature amplitude to 2.38 ℃ and maximum instantaneous heat transfer reduced by 1.61 W/m². The developed phase change mortar exhibits excellent heat storage performance along with sufficient mechanical strength for application on envelope structures to effectively regulate temperatures.

Solid Waste and Eco-Materials

Research Progress on Adsorption Behavior of Gibbsite and Boehmite

ZHOU Zongke, QIN Zonghua, WAN Quan, NIE Xin, YU Wenbin, YANG Shuqin

2024, 43(3):  878-890. 

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Gibbsite and boehmite are not only widely distributed aluminum hydroxide minerals in soil and water, but also important industrial raw materials and products. Their adsorption with inorganic non-metallic ions, inorganic metal ions, and organic compounds in the environment significantly affects the migration and enrichment of substances in the ground environment and the adsorption and removal of environmental pollutants. Due to structural characteristics and surface properties, their also have critical applications in the studying of efficient and economical adsorbents. Based on summarizing the structure and surface physicochemical properties of gibbsite and boehmite, this article reviews the adsorption behavior of various non-metallic ions, metal ions, and organic compounds on the surface of gibbsite and boehmite, with the hope of deepening the understanding of the role of aluminum hydroxide minerals in the cycling of ground environmental substances and expanding their industrial applications.

Axial Compressive Performance Experimental Study and Finite Element Analysis on Coral Aggregate Seawater Sea-Sand Concrete Columns Confined with CFRP-PVC Tube

ZHU Helong, XU Ruitian, LIANG Yuhan, LIANG Ying, YANG Qian, CHEN Zongping

2024, 43(3):  891-904. 

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To study the axial compression performance of coral aggregate seawater sea-sand concrete (CSSC) columns confined with carbon fiber reinforced polymer-polyvinyl chloride composite tube (CFRP-PVC), six specimens were subjected to axial compression load tests and finite element parameter analysis. The effects of the number of CFRP layers on inner and outer surfaces of PVC tube and void defects on the axial compression performance of composite column were studied. The results show that CFRP-PVC tube can effectively confine CSSC, placing it in a triaxial compression state. When CFRP is pasted on both the inner and outer wall with tube, it can effectively alleviate the characteristic of sudden failure. With one layer of CFRP pasted on the inner wall of PVC tube, better ductility and bearing capacity can be achieved under same conditions. With two layers of CFRP pasted on the outer wall of PVC tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defects only have a significant impact on ductility. A finite element model of CSSC column confined with CFRP-PVC tube is established based on ABAQUS software, accurately restores the failure process and CFRP damage morphology of composite columns under axial load. Parameter analysis shows that when the confinement coefficient of composite column is less than 0.3 or the aspect ratio is greater than 14.54, the load-displacement curve will lose strengthening section. Increasing the number of outer CFRP layers will slightly increase the stiffness of strengthening section. A bearing capacity calculation method suitable for CSSC column confined with CFRP-PVC tube is proposed, with an error of 1.2%.

Prediction and Analysis of Strength Response of Calcium Carbide Slag Excited Coal Gangue Geopolymer Based on Gaussian Process Regression Model

NING Huiyuan, ZHANG Ju, YAN Changwang, BAI Ru

2024, 43(3):  905-913. 

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The compressive strength of geopolymer is one of key factors in evaluating whether geopolymer can replace cement as a new building material, but relying only on many tests to test its strength wastes resources and improves costs. To solve this problem, the data of calcium carbide slag excited coal gangue geopolymer collected through early experiments, different mixing ratios, water-binder ratios, and ages were used as input parameters and compressive strength was used as output results. The strength response prediction model—Gaussian process regression (GPR) model was constructed based on machine learning methods. The geopolymer strength of different mixing ratios and ages was predicted by using the model, then the influence curves of each component content, water-binder ratio and age on the strength were established and the reasons were explored. The results show that the GPR model can predict the strength of geopolymer well after fitting the sample data, and the error is in the range of (-0.001 93~+0.001 83). The strength prediction of geopolymer with unknown compressive strength is made by the trained model, and the influences of each input parameters (calcium carbide slag content, coal gangue content, water-binder ratio, and curing age) on the strength were analyzed through the prediction results. It is found that the strength is closely related to the above variables, among which the calcium carbide slag content, coal gangue content and curing age have more influence on the strength.

Dynamic Compressive Mechanical Behavior of Basalt Fiber Reinforced Geopolymer Concrete under High Temperature

LENG Lingye, ZHANG Pengfei, LIANG Wenwen

2024, 43(3):  914-921. 

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In order to study the dynamic compressive mechanical behavior of basalt fiber reinforced geopolymer concrete (BFRGC) after high temperature, BFRGC specimens with fiber volume content of 0%, 0.1%, 0.2% and 0.3% were prepared, and dynamic impact tests of BFRGC specimens at 20, 200, 400, 600 and 800 ℃ were carried out. The results show that the static compressive strength, dynamic compressive strength and specific energy absorption of BFRGC specimens have obvious temperature enhancement effect and high temperature damage effect, and the peak strain shows a significant temperature plasticization effect. The temperature threshold of static compressive strength and dynamic compressive strength of BFRGC specimens is 400 ℃. With the increase of temperature, the static compressive strength, dynamic compressive strength and specific energy absorption of BFRGC specimens increase first and then decrease, and the peak strain increases continuously. The static compressive strength and dynamic mechanical properties of geopolymer concrete at room temperature and high temperature can be improved by adding appropriate content of basalt fiber, and the optimal content of basalt fiber is 0.1%.

Effect of Mineral Admixture on Static Yield Stress of Complex Binder Paste

YAN Peiyu, LIU Yu

2024, 43(3):  922-928. 

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The static yield stress of complex binder paste characterizes its internal microstructure build-up process, which affects the construction and 3D printing process of fresh cementitious materials. The effects of kind and dosage of mineral admixture on the varying regular of the static yield stress of complex binder paste were studied. It is found that the increase of fineness of mineral admixture reduces the thickness of water film on the surface of particles and results in the increase of the static yield stress of complex binder paste. The static yield stress of complex binder paste increases slowly during the initial period after mixing with water, and the paste structure build-up rate is small. The static yield stress of complex binder paste increases quickly after mixing with water about 1.5 h. It means that the linking of paste internal structure is almost non-destroyable, and paste begins setting and transforming to a solid.

Effects of Sodium Carbonate, Sodium Hydroxide and Water Glass Composite Activation on Properties of Geopolymer Cementitious Materials

JIANG Mingshen, LI Fei, ZHOU Li'an, NING Jiarui, ZHANG Zheng

2024, 43(3):  929-937. 

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Composite alkali activator was prepared by using sodium carbonate instead of sodium hydroxide to adjust the modulus of water glass. The effects of different alkali content and sodium carbonate replacement ratio on fluidity, setting time, and compressive strength of geopolymer cementitious materials were studied. The phase composition and microstructure of hydration products of geopolymer cementitious materials were analyzed through FT-IR, XRD, and SEM experiments. The results show that the combined effects of sodium hydroxide and sodium carbonate combined with composite water glass activators are superior to the effects of their individual combined with water glass activators. When alkali content is 6% (mass fraction) and the replacement ratio of sodium carbonate is 40%(mass fraction), the fluidity of geopolymer cementitious materials reaches 185 mm, and 28 d compressive strength reaches 94.4 MPa. The increase of replacement ratio of sodium carbonate can prolong the setting time of geopolymer cementitious materials. When the replacement ratio reaches 100%, the initial setting time and final setting time of geopolymer cementitious materials reach 372 and 420 min. When different alkali components are used as activators, similar hydration products are observed in geopolymer cementitious materials, mainly consist of amorphous aluminosilicate C-(A)-S-H gel.

Durability of Ternary Geopolymer Grouting Materials Based on Response Surface Methodology

CHEN Shijun, GONG Mulian, LIU Suyi, HUA Sixu, JIN Xiuwei, WANG Hao

2024, 43(3):  938-947. 

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To meet the durability requirements of synchronous grouting materials for tunnels under complex geological conditions, ternary geopolymer grouting materials were prepared using materials such as fly ash, slag and metakaolin, and their durability performance was studied. On the basis of exploring the physicochemical properties of raw materials, a durability test was designed using Box Behnken in response surface methodology. The test results were analyzed for significance, variance and three-dimensional response surface methodology. XRD, SEM and EDS were used to analyze the microstructure and hydration products of the polymer stone body. The results show that fly ash, metakaolin and slag can form a complementary effect, and their interaction has a significant impact on the erosion coefficient of grouting materials, which can effectively enhance their resistance to sulfate ion erosion. Prediction determination coefficient R²_pred is 0.932 8, the relative error of the experiment is 0.71%, and the model accuracy is high. Through optimization, the optimal mix ratio parameters are cement 45.183% (mass fraction, the same below), fly ash 20%, metakaolin 20% and slag 14.817%. The hydration products of geopolymer grouting materials are mainly calcite, C-A-S-H and N-A-S-H gel, which are closely connected and grow in a staggered manner, forming a dense three-dimensional spatial network structure support system, effectively enhancing the durability of the materials. The research results can provide reference for the subsequent research and production application of durability performance of ternary geopolymer grouting materials.

Effects of Mixing Mineral Admixtures on Properties of Ultra High Performance Wet-Joint Concrete

GE Keyu, LONG Yong, CHEN Luyi, LI Xin, LIU Kaizhi, WANG Yu, SUN Tao

2024, 43(3):  948-955. 

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Limestone powder and fly ash microbeads were used as mineral admixtures to adjust the properties of ultra high performance wet-joint concrete. The effects of limestone powder and fly ash microbeads on rheological properties, mechanical properties, shrinkage properties and impermeability of ultra high performance wet-joint concrete were studied by setting different mixing ratios. In addition, the hydration performance of ultra high performance wet-joint concrete was analyzed by hydration heat. The results show that when limestone powder is higher than 30% (mass fraction), with the increase content of limestone powder, the plastic viscosity of ultra high performance wet-joint concrete increases first and then decreases. The plastic viscosity of concrete is reduced by 38.0% when added with 50% limestone powder and 50% (mass fraction) fly ash microbeads. The addition of limestone powder promotes the early hydration of cement and improves the early compressive strength of ultra high performance wet-joint concrete, and the maximum growth rate of 3 d compressive strength is 11.6%. The autogenous shrinkage of ultra high performance wet-joint concrete is reduced by adding limestone powder and fly ash microbeads. The impermeability of ultra high performance wet-joint concrete is the best when the content of limestone powder is 30%, and the 28 d chloride ion diffusion coefficient is 0.15×10^-12 m²/s.

Effects of Mineral Admixtures on Frost Resistance and Renewability of Recycled Aggregate Concrete

CHENG Xu, ZHU Pinghua, WANG Xinjie, LIU Hui, WANG Huayu, WANG Yueying, CHEN Chuirui

2024, 43(3):  956-964. 

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In order to explore the effects of mineral admixtures on frost resistance and renewability of recycled concrete, three kinds of mineral admixtures, such as silica fume fly ash, fly ash silica fume and granulated blast furnace slag, were selected. Five groups of recycled aggregate concrete with different cementitious systems were prepared by different dosage combinations. The freeze-thaw test of recycled aggregate concrete was carried out by rapid freezing method. By measuring the relative dynamic elastic modulus, mass loss rate and compressive strength loss rate of recycled aggregate concrete during the freeze-thaw process, the frost resistance of recycled aggregate concrete with different cementitious systems was evaluated. The microstructure of recycled aggregate concrete after freeze-thaw cycle was observed by SEM. In addition, the recycled aggregate concrete after freeze-thaw cycle was crushed to obtain the second generation of recycled coarse aggregate, and the renewability of recycled aggregate concrete was evaluated according to its apparent density, crushing value, firmness value and water absorption. The results show that the mass loss rate and compressive strength loss rate of combination of 5% (mass fraction, the same below)silica fume +20% fly ash +20% slag +55% cement are significantly lower than those of combination of 5% silica fume, 5% silica fume +20% fly ash and 5% silica fume +20% slag, and the relative dynamic elastic modulus is also higher than that of other combinations. The second generation of recycled coarse aggregates of four combinations all meet the grade Ⅲ aggregate standard, which can be reused for structural concrete with strength grade of C25.

Freeze-Thaw Resistance of Activated Red Mud Based Cementitious Materials

LI Zichao, ZHU Junge, YUE Hongzhi, MA Laijun, ZHAO Haoyu, ZHONG Jiayi

2024, 43(3):  965-976. 

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The utilization of red mud resources is of great significance for the sustainable development of the alumina industry and environmental protection. The article studied the freeze-thaw resistance of red mud based cementitious materials prepared by red mud and thermally activated red mud as the main raw materials, and various solid wastes as auxiliary materials such as steel slag. The working conducted freeze-thaw experiments on gel samples cured for 14 and 28 d, and characterized the strength, phases, microstructure, porosity of samples before and after freeze-thaw using universal testing machines, XRD, SEM, industrial CT and other detection methods.The freeze-thaw damage mechanism in samples also was discussed based on characterization results. The results show that there are significant differences in mass loss, strength loss and microstructure of cementitious materials prepared by the synergistic method of red mud and different industrial solid wastes before and after freeze-thaw. The freeze-thaw resistance of cementitious material prepared by red mud and ordinary Portland cement is significantly better than that of other red mud solid waste cementitious materials. Its mass loss and strength loss of sample cured for 14 d before and after freeze-thaw are 23.68% and 50.75%, respectively. The mass loss of red mud-steel slag cementitious material prepared from heat-activated red mud was reduced by 16.30% after freeze-thaw compared to that before freeze-thaw.

Comprehensive Evaluation of Performance and Environmental Impact of Mineralization Curing Alkali Activated Solid Waste Cementitious Materials

WANG Yixiao, XU Yaoqun, ZHANG Ang, LIN Xinhao, YANG Manman

2024, 43(3):  977-986. 

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CO₂ mineralization curing solid waste cementitious materials can achieve diversified and reduced consumption of solid waste, while fixing and storing CO₂, which has dual carbon reduction benefits. To comprehensively consider the mechanical properties, carbon sequestration effect, and environmental impact of materials, this article selected compressive strength, carbon sequestration rate, carbon sequestration degree, carbonization efficiency, carbon emission, and energy consumption as evaluation indicators, and designed 11 sets of mixed proportion specimens for quantitative analysis and evaluation of comprehensive performance. The results show that compared with standard curing, the compressive strength and carbon sequestration effect of mineralization curing alkali activated solid waste cementitious materials have been significantly improved. Solid waste has excellent emission and consumption reduction advantages, but the use of alkali activator has a significant impact on the environment. When the mass ratio of fly ash, red mud, and steel slag is 7 ∶2 ∶1, the water-solid ratio, alkali adhesive ratio, and water glass modulus are 0.28, 0.26, and 1.2, the comprehensive performance of mineralization curing alkali activated solid waste cementitious materials is the best. The combination of CO₂ mineralization curing technology and solid waste utilization can unleash enormous carbon sequestration potential, which is an important measure to promote the synergistic effect of pollution reduction and carbon reduction.

Effects of Different Biomass Slags on Slurry Properties and Mechanical Properties of Autoclaved Aerated Concrete

XUE Wenhao, JIAN Shouwei, LI Baodong, HUANG Jianxiang, TAN Hongbo, MA Xiaoyao, WANG Caifeng

2024, 43(3):  987-994. 

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In the process of using biomass for power generation in power plants, the composition and properties of the incineration slag generated by different incineration processes are different, which poses significant challenges for its resource utilization. In this study, autoclaved aerated concrete (AAC) was prepared using biomass slag, cement and lime as the main raw materials. The effects of slags generated by two mainstream biomass incineration processes on the slurry properties and mechanical properties of AAC products were studied. Hydration products and micromorphology of AAC were also systematically studied by SEM and XRD. The results show that with the addition of mechanical grate incinerator slag(MGI), the initial fluidity decreases significantly, the fluidity loss of slurry increases, the gas volume decreases and the specific strength of AAC increases first and then decreases. When the MGI mass fraction is 28%, it is the best dosage to take into accont the strength and density of ACC, with the compressive strength and density are 3.6 MPa and 593.22 kg/m³, respectively. Due to the presence of a large amount of anhydrite and free calcium oxide in circulating fluidized bed combustion slag (CFBC), the solidification and hardening of the slurry are affected. With the increase of CFBC content, the initial fluidity of AAC slurry gradually increases, the gas generation volume increases, and the specific strength of AAC test blocks continues to decrease. In addition, the morphology and bulk density of tobermorite, hydration product, in AAC have a significant impact on the mechanical properties of the product.

Effect of Nano-SiO₂ on Optimum Gypsum Content in Supersulfate Cement

WANG Ruoyu, WANG Huanhuan, CHEN Heng, HOU Pengkun, LI Beibei

2024, 43(3):  995-1002. 

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There is an optimum gypsum content in supersulfate cement (SSC), although nano-SiO₂ (NS) can effectively improve the strength of SSC, but it can inhibit the hydration reaction of gypsum and aluminum phase, and the optimum gypsum content is changed. So optimizing the content of gypsum in the system is expected to further improve the performance of SSC. In this paper, the effect of mixing with or without 3% (mass fraction) NS on the mechanical and microscopic properties of SSC with gypsum content (5.0%~15.0%, mass fraction) was studied. The results show that the overall strength of SSC without NS develops slowly, the strength shows a downward trend with the increase of gypsum content at 1 d, and the optimum gypsum content is 7.5%. When NS is added, the strength increases significantly, the 3~28 d strength increases 100%~200%, the optimum gypsum content shows an increasing trend and the maximum strength is obtained when the gypsum content is 15.0% (the maximum content designed in this paper). NS lags gypsum consumption rate and inhibits ettringite formation, but does not affect the final consumption of gypsum. After the addition of NS, the chemical binding water content and gypsum consumption of SSC show an increasing trend, indicating that the demand for gypsum in the system increases. By exploring the change of the optimal gypsum content in NS-modified SSC, this paper provides new ideas for further reducing the amount of mineral powder, and improving the green and low carbon properties of SSC.

Composition Design and Property Regulation of High Content Phosphogypsum Hydraulic Cementing Material

LIU Aiping, WU Chiqiu, SHUI Zhonghe, LYU Wei, LIAN Jiuyang

2024, 43(3):  1003-1011. 

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The hydraulic phosphogypsum cementing material system studied in this paper is composed of 80% (mass fraction) phosphogypsum and a small amount of auxiliary cementing materials such as slag, cement, metacaolin, fly ash and silica fume. Mechanical properties test and molecular dynamics (MD) simulation are used to provide a basis for the composition design of high content phosphogypsum system, and then the strength shrinkage of the system is adjusted. The results show that when the content of phosphogypsum is fixed, the n(CaO)/n(SiO₂+Al₂O₃) molar ratio of the supplementary cementitious material (SCM) is close to 1, and the mechanical properties of the sample are the best. The results of molecular dynamics simulation on the atomic surface area and pore structure distribution of the model are consistent with the mechanical properties. The smaller the pore structure, the higher the compressive strength. On the atomic scale, O, Ca, Al and S atoms show high diffusion ability in molecular dynamics simulations with the molar ratio of n(CaO)/n(SiO₂+Al₂O₃) close to 1, which can give full play to alkali and sulfate excitation effects, and at the same time, increase the bond length of OO, Al—O and Si—O, resulting in unstable hydrolysis and promote the formation of calcium vanadite as a hydration product. Finally, by adjusting the types of auxiliary cementing materials, adding metakaolin, wollastonite and fly ash into phosphogypsum-slag-cement system, the problem of strength shrinkage at 90 d age is improved. It is of great significance to design and use phosphogypsum based on chemical composition and obtain better cementing materials.

Durability of Recycled Brick Powder ECC under Salt-Freezing Coupling Environment

CHU Liusheng, ZHANG Peng, HE Yuexi, YUAN Chengfang, CHENG Zhanqi

2024, 43(3):  1012-1020. 

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Recycled brick powder engineered cementitious composites (ECC) was prepared by replacing quartz sand in ECC with recycled brick powder. The mass loss rate and relative dynamic elastic modulus of recycled brick powder ECC under the erosion of NaCl solution, Na₂SO₄ solution and NaCl+Na₂SO₄ solution were studied by rapid freeze-thaw test of concrete. The damage model of ECC under salt frost erosion environment was established, and its durability was evaluated. The results show that after 300 freeze-thaw cycles, the mass loss rates of recycled brick powder ECC in water, NaCl salt solution, Na₂SO₄ solution and NaCl+Na₂SO₄ salt solution are 2.884%, 4.984%, 1.955% and 6.891%, respectively. The relative dynamic elastic modulus decreases by 6.468%, 16.300%, 24.303% and 39.861%, respectively. The frost resistance grade of recycled brick powder ECC is greater than F300 in the case of single salt-freezing, and the frost resistance grade is greater than F250 in the case of composite salt-freezing, which has good salt-freezing resistance. The established freeze-thaw damage model can better reflect the relationship between the damage degree D_n of ECC under different freeze-thaw media and the number of freeze-thaw cycles, which can provide an effective reference for structural durability design in severe cold regions.

Effect of Waste Glass Powder on Properties and Micro Pore Structure of Foamed Concrete and Its Value Engineering Analysis

YIN Pengxiang, LI Jing

2024, 43(3):  1021-1029. 

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The main composition of glass after grinding is similar to that of fly ash, which has potential pozzolanic activity. In order to improve the recycling rate of waste glass, the combination of foamed concrete and waste glass powder is used to improve the performance of foamed concrete, reduce cement consumption and enhance the recycling rate of waste glass. The effect of waste glass powder used as cementitious material to replace part of cement on compressive strength, dry density, drying shrinkage rate and softening coefficient of foamed concrete were studied. The results show that compressive strength of foamed concrete can improve by adding waste glass powder content within 0%~30% (mass fraction,the same below) of total mass of alternative cementitious materials. When waste glass powder content is 20%, the compressive strength of 28 and 56 d reach the maximum value, while the compressive strength of foamed concrete with 30% waste glass powder content reaches the maximum value at 120 d. Waste glass powder reduces the dry shrinkage value of foamed concrete, and the greater the content, the greater the reduction of dry shrinkage value, which helps to improve the problem of foamed concrete easily to crack. The addition of waste glass powder can significantly improve the softening coefficient of foamed concrete, which is conducive to its application in wet or underwater environments. In addition, from the perspective of changes of micro pore structure, the rules of mechanical and durability properties of foamed concrete caused by waste glass powder were explained. Finally, by analyzing the value of foamed concrete with waste glass powder, its environmental protection and economy were quantitatively proved.

Effect and Mechanism Analysis of CaF₂ Sludge on Ordinary Portland Cement

HU Chuan, YANG Wenwei, ZHAO Huanhuan

2024, 43(3):  1030-1038. 

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Solid waste utilization is one of the important ways to achieve the goal of “double carbon”. Taking solid waste CaF₂ sludge as cement admixture, the effect of CaF₂ sludge content on the properties of cement cementing material was investigated through compressive strength and slurry fluidity tests, and the mechanism was analyzed by XRD, SEM and TGA-DSC microscopic characterization tests. The results show that the addition of CaF₂ sludge can improve the early strength of cement cementing material. The compressive strength of cement cementing material with 8% (mass fraction) CaF₂ sludge is better. The addition of CaF₂ sludge leads to the decrease of slurry fluidity, but the addition of less than 10% (mass fraction) has no significant effect on slurry fluidity, compared with the cement without CaF₂ sludge, the slurry fluidity of the cement with 8% and 10% (mass fraction) CaF₂ sludge is reduced by 3.0%. CaF₂ sludge mainly plays a physical effect in cementing material, and CaF₂ sludge can form more crystallization sites to promote cement hydration. The dilution effect and agglomeration effect of CaF₂ sludge to cement increase significantly. The microscopic properties of cement with 8% (mass fraction) CaF₂ sludge are better.

Influence Mechanism of Waste Slurry in Mixing Station on Hydration Hardening of Cement

DING Zheng, LIAO Guosheng, LIAO Yishun, HE Junlin, HU Sida

2024, 43(3):  1039-1047. 

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In order to reduce the environmental impact of waste slurry from the mixing station and promote the recycling of waste slurry, the influence of waste slurry on hydration and hardening process of cement was studied through the setting time, compressive strength, resistivity, hydration heat, pore structure test and hydration product analysis and by using waste slurry to replace part of mixing water. The results show that after adding waste slurry, the setting time of sample is shortened, the compressive strength increases, the second exothermic peak in the DSC curves appears in advance, 3 d resistivity increases, the amount of hydration products increases, and the porosity decreases. The higher waste slurry content is, the better the effect of coagulation is, and the higher hydration product Ca(OH)₂ content is. When waste slurry content is 100% (mass fraction) and the storage time is 12 h, the initial setting time and the final setting time of sample are shortened by 69 and 87 min, respectively, compared with the blank group. At the age of 28 d, the production of Ca(OH)₂ increases, and the improving effect of strength of sample is the best, which increases by 36.2% at 3 d, 32.7% at 7 d, and 8.1% at 28 d compared with the blank group.

Ceramics

Effect of La³⁺ on Densification Process, Optical and Mechanical Properties of MgAl₂O₄ Transparent Ceramics

XING Yupei, LIU Peng, HAN Dan, ZHANG Jian, WANG Jun, MA Jie, XU Xiaodong

2024, 43(3):  1048-1057. 

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Magnesium aluminum spinel (MgAl₂O₄) transparent ceramics have excellent optical and mechanical properties, which have been widely used in bulletproof armor windows and high Mach fairing. To achieve densification of MgAl₂O₄ transparent ceramics, a relatively high sintering temperature is generally required. However, higher sintering temperature can lead to excessive grain growth of ceramics, which will affect its performance. Therefore, it is very significance for improving the performance and reducing costs of ceramics by introducing appropriate sintering aids to reduce its heat treatment temperature. In this article, the high-purity commercial MgAl₂O₄ powders were used as raw materials and La(OH)₃ powders were used as sintering aids. The MgAl₂O₄ transparent ceramics were fabricated using vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The evolution of microstructure and phase composition were tested by XRD and SEM. The optical and mechanical properties of transparent ceramics were characterized using UV-Vis-NIR spectrophotometer and multifunctional mechanical material testing machine, respectively. The results indicate that La³⁺ effectively improves the densification rate of ceramics in the early and middle stages of sintering, and inhibits grain growth of ceramics in the later stages of sintering. After adding 0.01% (mass fraction) La₂O₃, the optical and mechanical properties of MgAl₂O₄ are excellent. The HIP sintering temperature required to achieve optimal optical quality is decreased from 1 650 ℃ to 1 600 ℃ and the corresponding average grain size is reduced from 7 μm to 3 μm.

Effect of Silane Coupling Agent on Flow and 3D Printing Performance of Alumina Ceramic Pastes

MIAO Xinyu, LIU Shuangyu, LU Ping, ZHANG Fulong, Vasilieva Tatiana Mikhailovna, HUANG Chuanjin, WANG Liyan, WANG Binhua

2024, 43(3):  1058-1069. 

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In order to prevent cracks, holes, warpage and other defects in sintered ceramic parts, ceramic paste with high solid content and low viscosity is needed based on light-curing 3D printing technology. By testing the flow and curing proformances, the selection and ratio of resin monomers were optimized. KH550, KH560 and KH570 were used to modify the surface of Al₂O₃ powder to improve flow performance and stability of ceramic paste. The mechanism of silane coupling agent reducing the viscosity of Al₂O₃ ceramic paste was discussed. Al₂O₃ ceramic paste with a solid content of 75% (mass fraction) (volume fraction of 45.5%) and a viscosity of 4 540 mPa·s was obtained. An optimization method for the preparation of light-curing Al₂O₃ ceramic paste was proposed, which is expected to be helpful for the preparation of 3D printing Al₂O₃ ceramic paste with high solid content and low viscosity for complex ceramics.

Preparation of Cordierite Based Porous Ceramics byImpregnation Method

CHEN Dongli

2024, 43(3):  1070-1077. 

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Cordierite porous ceramics were prepared by organic foam impregnation method using kaolin from Panxi region as main raw material and adding a small amount of alumina and magnesium oxide, to study the effects of organic foam pretreatment time and slurry solid content on the microstructure and physical properties of cordierite porous ceramics. The results show that when m(kaolin) ∶m(Al₂O₃) ∶m(MgO)=66 ∶21 ∶13, the sintering temperature is 1 250 ℃ and the holding time is 0.5 h, the pore size of cordierite porous ceramics is 1.0~1.2 mm, the apparent porosity is 75.42%~96.27%, the compressive strength is 0.23~1.78 MPa, and the permeability coefficient is 18.58~25.86 cm·s^-1. When the mass fraction of slurry solid content is 40%, the water permeability and apparent porosity of cordierite porous ceramics produced by pretreatment of organic foam (NaOH solution soaking) for 6 h, and heat preservation at 1 250 ℃ for 0.5 h are 20.45 cm·s^-1 and 90.73%, respectively.

Finite Element Simulation of Stress Characteristics of Silicon Nitride Ceramic Penetrator under Calcium Carbide Furnace Sampling Conditions

ZHAO Qing, PAN Jiangru, MAO Yun, XU Yuanyuan, GUO Hongxin

2024, 43(3):  1078-1086. 

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In order to study the influences of mechanical properties on deformation of silicon nitride ceramic penetrator at high temperature, this paper modeled the penetrator which served as calcium carbide reclaiming by using SolidWorks software, coupled and simulated it in Workbench module of Ansys software to analyze the deformation condition of silicon nitride material under different mechanical properties. The results show that the maximum deformation variable of silicon nitride ceramic penetrator at 25 ℃ is 3.12 mm, and the change rate is 0.7%. With the increase of temperature, the deformation of silicon ceramic nitride penetrator decreases. At 1 800 ℃, the maximum deformation is 2.95 mm, and the change rate is 0.6%. The numerical simulation results show that it is feasible to use silicon nitride ceramics as penetrator, which can complete the reclaiming operation of calcium carbide furnace.

Glass

Research Progress of Near-Infrared Polarized Glass for Optical Isolators

HE Yongtao, MA Xiao, HU Yuhao, HOU Tianjiang, HU Lu, ZHAO Wenqi, FENG Jinyang

2024, 43(3):  1087-1102. 

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Near-infrared polarized glass is widely used in optical communication, optical modulator and laser industry because of its excellent polarization performance, high transmittance, low plug loss in the near-infrared band and excellent durability. This kind of material is prepared by forming a long rod or needle array of nano-metal particle structure in the glass, and the main preparation method is stretching-reduction method. The principle of polarization and performance testing of near-infrared polarized glass are introduced in detail. The current research status of main near-infrared polarized glass system and preparation technology of near-infrared polarized glass at home and abroad are reviewed. The development of near-infrared polarized glass is also prospected.

Effect of Crystallization Temperature on Properties of Silicon Fume Glass-Ceramics

ZHONG Kangdong, NIU Libin, ZUO Tongyao, ZHANG Guochen, CHEN Guofang

2024, 43(3):  1103-1109. 

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In order to respond to the national call for recycling of solid waste resources and adhere to the concept of green development, high-silicon waste silica fume was used as the main raw material, and CaO-Al₂O₃-SiO₂ series glass-ceramics were prepared by the overall crystallization method. The crystal phase type and micromorphology of glass-ceramics were characterized by TG-DSC, XRD, SEM, and the physical and chemical properties of glass-ceramics were tested. The studies show that after 2 h nucleation at 900 ℃ and the crystallization temperature is 1 150 ℃ for 2 h, glass-ceramics with anorthite as the main crystal phase can be prepared. When the crystallization temperature continues to rise to 1 200 ℃, a small amount of bubbles appear in glass-ceramics, and internal defects appear, which results in the decline of crystallization effect and physical and chemical properties. The glass-ceramics prepared by this method have excellent mechanical properties, the flexural strength is 93.58 MPa, the Vickers hardness is 845.62 HV_0.5, the bulk density is 2.88 g/cm³.

Refractory Materials

Application of FactSage Thermodynamic Calculation on Slag Corrosion Resistance of Refractories

GUO Weijie, ZHU Tianbin, LI Yawei, LIAO Ning, SANG Shaobai, XU Yibiao, YAN Wen

2024, 43(3):  1110-1122. 

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Commercial thermodynamic calculation software FactSage plays an important role in the analysis of slag corrosion process,therefore it has been widely used in the research of refractories. Application of thermodynamic calculation on slag corrosion resistance of refractories and thermodynamic calculation models which are commonly used in the slag corrosion resistance of refractories were introduced. The mechanisms, characteristics, applicable situations, accuracy and limitations of every model were discussed, and the detailed examples were given. Furthermore, the application examples of FactSage combined with other methods including ANSYS, kinetic analysis and MD simulation were given, aiming to avoid the limitations of thermodynamic calculation and comprehensively analyze the slag corrosion behavior. Lastly, the common problems of thermodynamic calculation were summarized, and the direction of further development was proposed.

Effect of Sintering Temperature on Microstructure and Properties of Anorthite Insulation Refractory

CHEN Xi, LIU Ying, YAN Wen

2024, 43(3):  1123-1132. 

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In this work, bauxite cement and clay were used as raw materials to prepare anorthite insulation refractory by foaming method. On the basis of analyzing the effect of sintering temperature (1 110~1 310 ℃) on the microstructure and properties of anorthite insulation refractory by XRD, SEM and thermal conductivity meter, the synthesis mechanism of anorthite insulation was studied. The results show that when the sintering temperature is between 1 110 ℃ and 1 160 ℃, anorthite begins to form, but the reactions between raw materials are not complete, the liquid phase content is less and the strength is lower. When the sintering temperature is between 1 210 ℃ and 1 260 ℃, the liquid phase content increases, the rate of anorthite formation was accelerates, the strength increases, and the samples have a low thermal conductivity. When the sintering temperature is 1 310 ℃, the liquid phase content increases rapidly, the linear shrinkage rate increases rapidly, and the samples have higher strength, but the bulk density increases significantly and the porosity decreases. At 1 260 ℃, the anorthite insulation refractory is prepared, with bulk density of 0.53 g/cm³, porosity of 82.6%, flexural strength of 1.15 MPa, compressive strength of 1.99 MPa, and thermal conductivity of0.101 W/(m·K) at 800 ℃.

Structural and properties Evolution of Al₂O₃-SiO₂ Refractories under Simulated Hydrogen-Based Shaft Furnace Condition

XIE Fubo, LI Yawei, LIAO Ning, SHI Chenglong, CAI Guoqing, QIN Jiantao

2024, 43(3):  1133-1142. 

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Currently, research on hydrogen-based shaft furnaces mainly focuses on the reduction thermodynamics and kinetic processes and furnace structure design, while research on refractories is rare. Based on the strong reducing environment of H₂/CO mixed gas, this study simulated the service conditions of atmospheric pressure hydrogen-based shaft furnaces, and researched the performance changes and instability mechanisms of typical Al₂O₃-SiO₂ refractories after reduction treatment. The results show that under the condition of V(H₂) ∶V(CO)=5 ∶2, the heat treatment temperature rises from 450 ℃ to 950 ℃, and the reduction ability of mixed gas to Al₂O₃-SiO₂ refractories is gradually enhanced. Under current conditions, the two key factors leading to the instability of Al₂O₃-SiO₂ refractories are the Fe₂O₃ content and the phosphate binder. 1) When the Fe₂O₃ content in Al₂O₃-SiO₂ refractories is high, it is easily reduced to elemental iron in the H₂/CO atmosphere. At the same time, this situation will lead to a certain degree of volume change and significant decrease in mechanical properties of Al₂O₃-SiO₂ refractories. 2) Phosphate-bonded Al₂O₃-SiO₂ refractories materials also face phosphate volatilization, leading to an increase of apparent porosity and a decrease in structural stability. However, it is found that when the Fe₂O₃ content in the phosphate-bonded alumina-mullite brick is lower and accompanied by a certain amount of TiO₂, the refractories exhibits good resistance to H₂/CO gas reduction. By comparing the mechanical properties of Al₂O₃-SiO₂ refractories in CO atmosphere and H₂/CO atmosphere, it is found that the heat treatment condition which holding 3 h at 850 ℃ in the atmosphere of V(H₂) ∶V(CO)=5 ∶2 has a stronger reducing ability than the heat treatment condition which holding 100 h at 500 ℃ in CO atmosphere.

Road Materials

Morphological Characteristic Parameter Analysis and Performance Evaluation of Road Aggregate

WANG Yongliang, YI Jiangtao, LIU Yue

2024, 43(3):  1143-1152. 

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The long-term anti-skid performance of asphalt pavement depends on the skid-resistant and abrasion-resistant performance of aggregates, so it is very important to calculate the morphological characteristics of aggregates accurately and quickly. In the research, 88# calcined bauxite, a new type of high skid resistance road aggregate, was introduced. Image-Pro-Plus 6.0 (IPP), IBM SPSS Statistics 26.0 (SPSS) and other digital image processing softwares were used to analyze and evaluate the morphological characteristics of aggregates. Meanwhile, grey entropy correlation analysis was carried out to obtain the grey entropy correlation degree between the aggregate morphological characteristic parameters and polished stone value (PSV) under different polishing times. The results show that the morphological characteristic parameters of each aggregate can be accurately obtained by IPP software, and compared with traditional aggregates, 88# calcined bauxite has richer angular characteristics and higher roughness. According to grey entropy correlation analysis, the correlation between fractal dimension and PSV is the most significant.

Influence of Steel Slag Fine Powder on Properties of Asphalt Mortar and Mixture

XU Xinqiang, HAN Fangyuan, CHEN Weibin, XU Tengfei, CUI Yu

2024, 43(3):  1153-1161. 

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In order to investigate the effect of steel slag fine power (SSFP) on performance of asphalt mortar and mixture, SSFP was prepared using steel slag with a particle size less than 5 mm. With limestone powder (LP) as a comparison group, the performance of SSFP asphalt mortar was analyzed and evaluated with different filler-asphalt ratio (F/A), and the effect of SSFP on the performance of asphalt mixture was also investigated. The results show that, compared with LP, SSFP improves the high temperature performance, low temperature performance and fatigue performance of asphalt mortar and mixture, with the greatest improvement in low temperature performance, 190.57% for bending creep stiffness modulus of SSFP asphalt mortar and 9.93% for low temperature bending fracture strain of mixture. The increase of F/A improves the high temperature performance of asphalt mortar, but damages its fatigue performance and low temperature performance. The application of SSFP in asphalt mixture has strong feasibility and popularization value.

Influence of Content of Reclaimed Polyurethane Concrete on Pavement Performance of Recycled Mixture

XU Shifa, ZHANG Ziqian, WU Hongliang, GUO Qianyun, MA Haotian, HAN Haoyue

2024, 43(3):  1162-1171. 

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The recycling of reclaimed polyurethane concrete (RPC) has not been explored yet. Therefore, this paper proposes an indoor simulation preparation method of RPC. Polyurethane recycled mixture (PRM) with 7 kinds of RPC content was prepared with polyurethane as binder. The bonding properties of polyurethane and RPC interface and the influence of RPC content on the road performance and durability of PRM were studied, and the prediction model of PRM road performance and durability with RPC content was established. The results show that RPC meets the relevant technical requirements of the specification for aggregates. The los angeles wear loss, soft stone content, sand equivalent and angularity are higher than those of limestone, and the crushing value and apparent density are lower than those of limestone. The bonding performance of the interface between polyurethane and RPC is superior; with the increase of RPC content, the road performance and durability of PRM show a downward trend. Under the same RPC content, splitting strength of PRM gradually decreases and tends to be stable with the increase of freeze-thaw cycles and aging time. With the increase of RPC content, the splitting strength of PRM decreases more significantly with the increase of freeze-thaw cycles and aging time.

Effect of Steel Slag Fine Aggregate on Road Performance of Cement Stabilised Sandstone Base Layer

LI Chao, JIANG Yunliang, LI Shaoyong, YAN Feng, TANG Changxi, LI Xiaolong

2024, 43(3):  1172-1180. 

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The application of steel slag to pavement subgrade can improve the comprehensive utilization of steel slag as well as help to reduce the consumption of natural sand and gravel materials. In order to analyse the effect of steel slag fine aggregate on road performance of cement stabilised sandstone base layer (CSSB), the compressive strength, splitting strength, shrinkage properties and water stability of CSSB were comparatively analysed under different steel slag fine aggregate replacement limestone fine aggregate, and SEM combined with energy spectroscopy were used to reveal the effect of steel slag fine aggregate on microstructure of CSSB. The results show that steel slag fine aggregate can effectively improve late strength of CSSB, in which the 60 d strength of CSSB with 100% steel slag fine aggregate replacement rate increases by 18.7% compared with that of undoped steel slag specimens, however, there is a certain negative effect on the early strength of CSSB. Steel slag fine aggregate can improve shrinkage properties of CSSB, and the higher the doping amount, the more obvious the improvement of the performance. Although steel slag fine aggregate can improve the long-term water stability of CSSB, it will reduce its short-term water stability to some extent. Compared with the undoped steel slag samples, m(Ca)/m(Si) ratio in the interface transition zone of CSSB with 100% steel slag fine aggregate replacement rate at the age of 28 d reduces by 62.95%, and the C-S-H gel is obviously increases, with a denser structure. The study shows that by controlling the reasonable content, steel slag fine aggregate can be used as a substitute aggregate for traditional sand and gravel fine aggregate, and has a good application prospect in the pavement base layer.