Table of Content

Volume 44 Issue 1
15 January 2025

Previous Issue 　

Cement and Concrete

Effect of LDHs-NO₂ on Properties of Cement Mortar and Corrosion of Steel Bar

ZHANG Yi, ZHANG Biao, DENG Xiangwen, HE Hongjie

2025, 44(1):  1-10.  doi:10.16552/j.cnki.issn1001-1625.2024.1003

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In this paper, NO^-₂ was intercalated into the interlayer of Zn-Al-LDHs (layered double hydroxides, LDHs) by hydrothermal method to prepare modified hydrotalcite (LDHs-NO₂), and LDHs-NO₂ was characterized. The effect of different LDHs-NO₂ content on the fluidity, mechanical properties, chloride ion diffusion coefficient, pore structure, chloride ion adsorption of cement mortar and corrosion resistance of steel bar was investigated. The test results show that the compressive strength and flexural strength of cement mortar are improved, and the chloride ion diffusion coefficient and porosity are decreased by adding different content of LDHs-NO₂ into cement mortar. Compared with the reference group, the performance of cement mortar with 2% (mass fraction) LDHs-NO₂ is the most significant. Then, with the continuous increase of LDHs-NO₂ content (4%, 6%), the fluidity and mechanical properties of mortar decrease, but still higher than the reference group. The porosity of cement mortar has increased, but it is still lower than the reference group. LDHs-NO₂ achieves the adsorption of Cl^- through interlayer ion exchange, which is accompanied by the release of interlayer NO^- ₂ during the adsorption of Cl^-. LDHs-NO₂ can effectively delay the corrosion of steel bars in cement mortar, and the more LDHs-NO₂ content in a certain range, the better the corrosion resistance of steel bars.

Effect of Typical Pore-Blocking Curing Agent Solution Curing on Surface Properties of Different Mortars

ZHANG Yu, YANG Jinbo, JI Shanhao, ZHANG Ze

2025, 44(1):  11-20.  doi:10.16552/j.cnki.issn1001-1625.2024.0960

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In this paper, the effects of three typical pore-blocking curing agent solutions, sodium silicate solution, sodium bicarbonate solution, complex sodium silicate solution and sodium hydroxide solution, on the surface properties of different mortars were investigated. The surface rebound strength, surface capillary water absorption and surface carbonization depth of mortar after curing with curing agent solution were measured, and the effect of design parameter of main mix ratio of mortar on the curing effect of surface property of mortar was compared and analyzed. The results show that the curing system of early curing agent solution can effectively improve the surface properties of mortar. After curing with 5% (mass fraction) sodium bicarbonate curing solution, the mortar surface rebound strength increases by 18.8% on average, the surface capillary water absorption decreases by 21.0%, and the surface carbonization depth decreases by 14.1%. In addition, the curing effect of curing agent solution on mortar with high water-cement-density ratio is more obvious.

Effect of Nano-C-S-H Seeds Early-Strength Agent on Early Hydration of Cement

ZHANG Jinlong, TANG Mengxiong, ZHONG Conghao, HU Jiabing, SHAO Qiang, ZHONG Kaihong

2025, 44(1):  21-30.  doi:10.16552/j.cnki.issn1001-1625.2024.0788

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Investigating the impact mechanisms of nano-C-S-H seeds early-strength agent on the early hydration of cement is pivotal for advancing their application in practical engineering. By comparing mechanical properties and hydration heat tests, the effect of varying content of synthesized nano-C-S-H and the differences in effects compared to commonly early-strength agents were analyzed. Additionally, XRD, TG-DTG and SEM were employed to elucidate the effect of nano-C-S-H on the cement hydration process. The results demonstrate that increasing the content of the synthesized nano-C-S-H seeds early-strength agent leads to an initial rise in 1 d compressive strength, hydration heat release rate, and total hydration heat, followed by a decline. The optimal early-strength effect is observed at content of 0.6% by mass of the cementitious materials. When the content of nano-C-S-H is 0.6%, the nano-C-S-H seeds early-strength agent has the best early-strength effect and has no negative effect on the compressive strength at 7 and 28 d. Compared to the blank group, the addition of nano-C-S-H significantly enhances the hydration rate during the cement induction period, as well as the formation and density of AFm, AFt and C-S-H gels during the 1 d age, but has no significant effect on the formation of hydration products at the middle and late ages.

Sulfate Corrosion Behavior in Solution Fully Soaked Magnesium Potassium Phosphate Cement Slurry

HOU Yuying, YANG Jianming, XU Xiaohui, HU Xuexin, CHEN Weiliang, HU Xiamin, JIANG Dequan, XIONG Caiqiang, LI Tao

2025, 44(1):  31-39.  doi:10.16552/j.cnki.issn1001-1625.2024.0917

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Through macro performance test, chemical analysis and microscopic analysis, this paper studied the diffusion of sulfate ions and strength development of magnesium potassium phosphate cement (MKPC) specimens immersed in a Na₂SO₄ solution with a mass fraction of 5%. The results show that with the extension of soaking age, the content of sulfate ions inside the specimens and the depth of erosion gradually increases. The relationship between the depth of erosion of sulfate ions in MKPC specimens and the sulfate ion content generally fits a second-order or third-order polynomial (with a correlation coefficient R² greater than 0.998). By solving the analytical expression using Fick's second law of diffusion with established boundary conditions, the diffusion coefficient of sulfate ions in MKPC specimens is in the range of 10^-7 mm²/s, which is one order of magnitude lower than that of Portland cement concrete. The diffusion coefficient of sulfate ions in MKPC specimens exhibits a decreasing trend for soaking age not exceeding 180 d. After more than 180 d, the diffusion coefficient of sulfate ions in MKPC specimens gradually increases. After 360 d of soaking, the diffusion coefficient of sulfate ions in MKPC specimen is 3.9×10^-7 mm²/s, and the sulfate ion content at 2 mm from the surface is 0.218% (mass fraction). The strength of MKPC specimens increases initially and then decreases as the soaking age extends, following a similar trend to that of the diffusion coefficient of sulfate ions. After 360 d of soaking, the loss rates of flexural and compressive strength of MKPC specimens are both less than 5%.

Preparation of Nanofiber and Its Effect on Water Invasion Resistance of Oil Well Cement Paste

MA Jiang, TANG Wenli, SONG Huiguang, LIU Kaiqiang, DENG Lin, PEI Xuefeng, ZHANG Xingguo

2025, 44(1):  40-48.  doi:10.16552/j.cnki.issn1001-1625.2024.0379

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Aiming at the problems that the oil-recovery-efficiency of oilfield in very high water-cut stage is low and polymer water invasion resistance agents reduce the early hydration rate of cement paste and cementing quality of high-pressure water-cut stratum, this study was carried out to prepare nanofiber as a new type of water invasion resistance agent using plant cellulose fibers combining wet ultrafine ball milling and 2,2,6,6-tetramethylpiperidine oxide (TEMPO) oxidation methods. The effect of nanofiber on the rheological properties, consistency time, compressive strength and water invasion resistance of cement paste was investigated. The results show that the nanofiber have the effects of increasing viscosity and promoting early hydration of cement paste. When the mass fraction of nanofiber increases to 0.2%, the liquidity index of cement paste decreases from 0.849 to 0.557, the yield stress increases from 2.305 Pa to 10.061 Pa, the consistency time slightly reduces from 260 min to 219 min, and the 14 d compressive strength improves from 26.8 MPa to 41.0 MPa. The nanofiber could enhance the cohesion of cement paste by bridging and adsorption, and increase the hydration rate and early compressive strength of cement by changing nucleation site, which is beneficial for improving the bonding quality between cement stone and stratum rocks and cementing quality.

Effects of Different Dopants on Wave-Absorbing Properties of Cement-Based Composites

ZHANG Yan, XIE Jianbin, WANG Dafu, LI Kenu, YANG Le, CHEN Zimin

2025, 44(1):  49-58.  doi:10.16552/j.cnki.issn1001-1625.2024.0718

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Incorporating suitable wave-absorbing agents into cement and performing appropriate electromagnetic modification is an effective way to realize electromagnetic wave-absorbing. In this paper, cement-based composites were prepared with slag, graphite and ferrite as wave-absorbing agents, and mechanical property test, microstructure test and reflectance test were carried out to investigate the effects of different dopants and sample thickness on the wave-absorbing properties and mechanical properties of cement-based composites. The results show that the cement-based composites have the best wave-absorbing performance when the doping of slag is 30% (mass fraction) and graphite is 5% (mass fraction), and there exists the best matching layer thickness. The reflection loss is -40.84 dB at 2.65 GHz when the thickness is 36 mm. When the cement-based composite is composed of 30% slag, 10% (mass fraction) ferrite, and the matching layer thickness is 36 mm, the cement-based composites have the lowest reflectivity of -26.63 dB at 2.53 GHz. Both slag and ferrite reduce the strength of cement-based composites, and graphite (no more than 5%) is able to fill in mortar pores at the early stage of cement hydration, which enhances early mechanical properties.

Experimental Study on Cracking Resistance of Polyvinyl Alcohol Fiber Concrete under Dynamic Loading

HAN Zimo, YANG Guoliang, LI Feng, ZHANG Zhifei, BI Jingjiu, ZHAO Kangpu, LIU Yi

2025, 44(1):  59-68.  doi:10.16552/j.cnki.issn1001-1625.2024.0794

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In order to investigate the effect of fiber volume content on the cracking resistance of polyvinyl alcohol fiber engineered cementitious composite (PVA-ECC) under dynamic loading, impact tests were carried out on the notched semi-circular bending (NSCB) specimen with five fiber volume content (0%, 0.75%, 1.50%, 2.25%, 3.00%) by separated Hopkinson pressure rod device (SHPB). Combined with the dynamic fracture process recorded by high speed camera, the dynamic cracking toughness and energy dissipation characteristics of material were analyzed, and the fractal dimension of cracking growth path was calculated according to the theory of box dimension. The results show that the dynamic cracking toughness of material increases first and then decreases with the increase of fiber volume content, and the dynamic cracking toughness is higher when the fiber volume content is in the range of 1.50% to 2.25%. The dissipative energy increases with the increase of fiber content in the range of 0.75% to 2.25%, but the total absorbed energy decreases with the increase of fiber content. Under constant velocity impact, the fractal dimension of final crack growth path after material failure is the highest when the fiber content is 2.25%, and the cracking resistance is best. When the fiber content is more than 2.25%, the fractal dimension of cracking growth path shows a downward trend, and the fiber cracking resistance gain effect decreases.

Dynamic Mechanical Properties of Steel-Basalt Hybrid Fiber Concrete after High Temperature

RAN Qiushuo, XU Zehui, QI Wenchao, LIU Lei

2025, 44(1):  69-80.  doi:10.16552/j.cnki.issn1001-1625.2024.0731

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In order to study the influence of high temperature on the dynamic mechanical properties of steel-basalt hybrid fiber reinforced concrete (HFRC), a φ50 mm split Hopkinson pressure bar (SHPB) system was used to carry out dynamic compression and dynamic splitting experiments on steel fiber reinforced concrete (SFRC), basalt fiber reinforced concrete (BFRC), and hybrid fiber reinforced concrete at different temperatures (25, 100, 200, 400, 600, 800 ℃). The volume content of steel fiber and basalt fiber was 1% and 0.2%, respectively. The dynamic stress-strain process under different temperature conditions was obtained. The corresponding dynamic compressive strength, dynamic splitting strength and peak strain were obtained. The results show that the residual mechanical properties of specimens can be ensured at high temperature by adding basalt fiber, and the dynamic splitting tensile strength of specimens can be improved obviously by adding steel fiber. Temperature damage softening has an important effect on the mechanical properties of concrete. The addition of steel fiber and basalt fiber can effectively relieve the deterioration of high temperature, and steel-basalt hybrid fiber concrete exhibits better mechanical properties under normal and high temperature conditions.

UHPC-NC Interface Feature Recognition and Bonding Performance Based on Digital Image Technology

ZHANG Jiangjiang, SUN Wen, XIAN Xuelei, LI Ruize, ZHAN Shumin, WANG Jiaze

2025, 44(1):  81-89.  doi:10.16552/j.cnki.issn1001-1625.2024.0817

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In order to more accurately analyze the influences of ultra high performance concrete-normal concrete (UHPC-NC) interface features on bonding strength, this paper quantitatively characterized the three-dimensional feature information of the substrate surface based on digital image technology, and studied the influences of different substrate surface roughness and coarse aggregate area on the interface bonding strength. The results indicate that there is a strong correlation between the substrate surface roughness and the area of coarse aggregate, and the correlation coefficients between the contour arithmetic mean deviation R_a and standard deviation S_td of the obtained profiles and the coarse aggregate area S_c are 0.838 and 0.855, respectively. The substrate surface roughness increases with the increase of coarse aggregate area. The failure load of the interface group specimen treated with high-pressure water jet on the substrate surface increases by 143.0% to 240.0% compared to the smooth interface group specimen, while the high-pressure water jetting treatment interface group specimen could obtain 53.4% to 89.6% of the overall specimen failure load. The surface characteristics of NC substrate are key factors affecting the interface bonding strength. The characteristic parameters of the substrate surface roughness, the profile arithmetic mean deviation R_a, standard deviation S_td and coarse aggregate area S_c, are positively correlated with the interface bonding strength, and their correlation coefficients are 0.935, 0.927 and 0.959, respectively. The interface bonding strength increases with the increase of substrate surface roughness and coarse aggregate area.

Interfacial Bond-Slip Performance of Square Aluminum Alloy Tube-Seawater Sea-Sand Geopolymer Concrete

LU Junhui, LYU Hai, LI Junyuan, YANG Haifeng, CAO Huayi

2025, 44(1):  90-100.  doi:10.16552/j.cnki.issn1001-1625.2024.0848

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The bond-slip performance of square aluminum alloy tube-seawater sea-sand geopolymer concrete (SSGC) structure is the cornerstone to ensure its ability to work together. In order to study the interfacial bond-slip performance of square aluminum alloy tube-SSGC, nine specimens were made for push-out test with concrete strength, diameter-thickness ratio and length-diameter ratio as research parameters. The load-slip curve of specimen, the longitudinal strain distribution on the surface of the square aluminum alloy tube and the influence of the research parameters were analyzed by tests. Based on the test data, the calculation formula of bond strength and bond-slip constitutive equation of square aluminum alloy tube-SSGC were proposed. The results show that the typical load-slip curve of square aluminum alloy tube-SSGC can be divided into four stages, namely linear rising stage, nonlinear rising stage, slow falling stage and residual horizontal stage. The longitudinal strain on the surface of the square aluminum alloy tube shows a exponential distribution along the height direction, and increases from the loading end to the free end. The bond strength of specimen decreases with the increase of the diameter-thickness ratio and the length-diameter ratio.

Evolution Law of Bond Performance Between Steel Bar and Nano-TiO₂ Concrete after High Temperature

ZHAO Yanru, LI Huan, LI Yuping, JIA Zongming, SHI Lei

2025, 44(1):  101-111.  doi:10.16552/j.cnki.issn1001-1625.2024.0693

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Through the central pull-out test and high temperature test, the influence of different nano-TiO₂ content on the bond performance of reinforced concrete after high temperature was analyzed. The relationship between residual compressive strength and ultimate bond stress damage degree of reinforced concrete with different nano-TiO₂ content after high temperature was discussed. The results show that after high temperature, the addition of appropriate amount of nano-TiO₂ can enhance the bond performance of reinforced concrete and delay the high temperature damage of concrete. However, when the content of nano-TiO₂ exceeds 2% (mass fraction), the bond performance between steel bar and concrete is weakened. The prediction formula of bond strength of reinforced concrete with different nano-TiO₂ content after high temperature is established. The experimental value is in good agreement with predicted value.

Development Law of Air Content of Hydraulic Concrete under Different Air Pressure Environments

DAI Wei, YANG Tao, SUN Yanmei, ZHANG Ruiyu, QIN Xiaofeng, CAI Junyi, LI Yang

2025, 44(1):  112-123.  doi:10.16552/j.cnki.issn1001-1625.2024.0935

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Southwest and northwest part of China has a large terrain height difference, relatively low air pressure. Hydraulic concrete is often exposed to low air pressure environment, resulting in a reduction of its durability. This paper investigated the influences of different air pressure environments on air content of hydraulic concrete and the performance of air-entraining agent solution. The results show that low air pressure significantly weakens the air-entraining capacity of air-entraining agent solution, and the rate of bubble decay is higher. Range and variance analysis show that in 101 and 80 kPa environments, the degree of influence of each factor on air content is in descending order: air-entraining agent dosage, water-cement ratio, and fly ash dosage. In 50 kPa environment, the influence of each factor on air content is in descending order: water-cement ratio, air-entraining agent dosage, and fly ash dosage. With the reduction of air pressure, the air content of hardened concrete decreases, the bubbles in the low air pressure environment are more likely to converge to form large bubbles, and the pore structure of hydraulic concrete is gradually deteriorated after hardening, which is specifically reflected in the serious deterioration of the pore structure of the specimen. The average pore diameter and average pore spacing coefficient of hardened concrete increase, and the air content of hardened concrete is significantly smaller than that of fresh concrete. The low air pressure environment retards the cement hydration process, resulting in a decrease in the stability of bubbles in the matrix, which in turn causes a decrease in air content of hardened concrete.

Forming Methods and Properties of Ceramsite Foam Concrete

GENG Chunlei, GUO Hongda, DONG Yang, ZHANG Dong, GONG Siyu, LI Qiao

2025, 44(1):  124-132.  doi:10.16552/j.cnki.issn1001-1625.2024.0900

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Based on the forming methods of ceramsite foam concrete, this paper studied the influences of the pretreatment method of ceramsite, the incorporation method of ceramsite and the adding method of mixing water on the work performance, dry and wet density, compressive strength, bottom grip performance and ceramite distribution of ceramsite foam concrete, and determined the optimal forming methods of ceramsite foam concrete. The results show that slurry expansion degree can be effectively improved by the saturated water pretreatment method of ceramsite and the method of adding mixing water twice. Different forming methods have little influence on the aggregate expansion degree of ceramsite foam concrete. The dry and wet density of ceramsite foam concrete is affected by the incorporation method of ceramsite and mixing water. The adding method of mixing water twice and wet mixing of ceramsite are beneficial to improve the compressive strength of ceramsite foam concrete. The pretreatment method of ceramsite determines the bottom grip performance, and the adding method of mixing water also affects the bottom grip performance.

Time-Varying Study on Effect of Coarse Aggregate on Concrete Performance under Environmental Action

ZHANG Wenjing, ZHANG Rongling, ZHANG Yan, WANG Yulin, ZHANG Fukui, WANG Xianlong, AN Kangle

2025, 44(1):  133-141.  doi:10.16552/j.cnki.issn1001-1625.2024.0053

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In order to explore the effects of gabbro (SMK), granite (LBH), diabase (HYS), gneiss (LFS), silicified dacite (SSH) on the properties of concrete under freeze-thaw and sulfate corrosion environment, the macro-micro tests of concrete such as compressive strength and pore structure were carried out to study the time-varying law of concrete prepared by five kinds of coarse aggregates undergoing different freeze-thaw cycle times under semi-immersion of Na₂SO₄ solution. The results show that with the increase of freeze-thaw cycle times, the apparent loss of HYS concrete and LFS concrete is more serious, the internal part of coarse aggregate is loose, the strength is reduced, and the interfacial bonding strength between aggregate and cement mortar is reduced. At the beginning of freeze-thaw cycle test, the pores in the five groups of concrete specimens expand rapidly and many new pores generate. The number of small pores increases, the number of large pores decreases, and the compressive strength also increases. In the later stage of freeze-thaw cycle, the large pore size in specimen increases, the coarse aggregate in LFS concrete is loose and expanded, and the concrete cracking is aggravated. LFS concrete has the largest pore expansion, followed by the HYS concrete pore expansion. The pore size variation trend of the five groups of concrete specimens is basically the same. The strength of concrete decreases and is positively correlated with the pore change, but the strength reduction is related to the performance of coarse aggregate itself. This study can be crude in freeze-thaw and sulfate corrosion environment. The research results can provide reference for quality control of coarse aggregate and sustainable utilization of concrete under freeze-thaw sulfate corrosion environment.

Performance Evolution Law of Silane-Impregnated Concrete under Coupling Effect of Irradiation-Wet/Dry Cycling-Chloride

MA Jinliang, HU Juan, WANG Wei, JU Zhicheng, YANG Haicheng, FAN Zhihong

2025, 44(1):  142-150.  doi:10.16552/j.cnki.issn1001-1625.2024.0920

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In order to clarify the influences of typical harsh marine environments on the performance evolution of silane-impregnated concrete, three different simulated environmental experiments were designed, including immersion, ordinary wet/dry cycling, and irradiation wet/dry cycling. After exposure to these environments for 90 and 180 d, experiments on contact angle, water absorption ratio, alkyl content and chloride content were carried out. The results indicate that the performance evolution of silane-impregnated concrete is closely related to the exposure environment and the action time. The silane gradually fails and destroys in the typical marine environments. The initial contact angle of freshly impregnated concrete is 97.0°, which decreases to 73.1°, 46.4°, 28.2° after 180 d of immersion, ordinary wet/dry cycling, and irradiation wet/dry cycling, respectively. The alkyl content at 1 mm of silane-impregnated concrete is lower than that at 2 mm. Compared with immersion, short-term irradiation wet/dry cycling reduces the water content in surface pores of concrete, facilitating the dehydration condensation reaction of silane, reducing the early water absorption ratio and improving the chloride resistance of silane-impregnated concrete. Specifically, the irradiation wet/dry cycling group exhibits the lowest water absorption ratio and chloride diffusion coefficient at 90 d. However, with the extension of irradiation wet/dry cycling, the degradation of silane accelerates, and the water absorption ratio and chloride diffusion coefficient at 180 d both increase significantly.

Solid Waste and Eco-Materials

Research Progress of Migration Law of Harmful Elements and Environmental Risk Assessment in Process of Coal Fly Ash Placement and Utilization

HAO Longlong, QIN Shenjun, PANG Wei, LI Shenyong, LYU Dawei, ZHENG Xue, HOU Jiajia, MEN Changquan

2025, 44(1):  151-168.  doi:10.16552/j.cnki.issn1001-1625.2024.0862

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Coal fly ash, as a bulk aluminosilicate solid waste, poses environmental risks due to the migration of harmful elements during its placement and resource utilization. This paper reviews the occurrence state of harmful elements in coal fly ash, the migration of these elements during placement and utilization, influencing factors, and methods for environmental risk assessment. The majority of harmful elements in coal fly ash primarily exist in residual or iron-manganese oxide states. During the placement process, the migration of harmful elements in coal fly ash is influenced by factors such as the geochemical properties of elements, particle size, and pH value, exhibiting different characteristics. In the process of resource utilization, harmful elements also show different migration rules. During the process of soil improvement using coal fly ash, the migration of harmful elements to the surface or deep soil layers varies due to their different properties, but there is a tendency for migration to the surface soil over time. In the preparation of functional materials based on coal fly ash, metal harmful elements mainly migrate into the product, while non-metal harmful elements primarily migrate into the waste liquid. In the extraction process of valuable elements from coal fly ash, harmful elements migrate into waste liquid, waste residue, and products, but specific details are currently lacking. Finally, this paper summarizes existing standards and regulations related to the environmental risk of harmful elements in coal fly ash, as well as environmental risk assessment methods, analyzes existing problems, and proposes research prospects.

Research Status of Hydration and Activation of Slag

YANG Siyu, HUANG Wen, ZHAO Jiaqi, ZHANG Wenming, WANG Lei, WANG Jianfeng

2025, 44(1):  169-179.  doi:10.16552/j.cnki.issn1001-1625.2024.0996

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With the decline in ore grade and the adjustment of production processes within the steel industry, the composition and structure of slag changes, resulting in the decrease of cementitious activity of slag and rendering its utilization in cement-based materials. Based on the composition and structure of slag, this paper analyzes the potential factors influencing the hydration activity of slag. It reviews traditional slag activation methods and their corresponding issues, elucidates the mechanism of action, advantages, and disadvantages of alkanolamine complexation activation method, and introduces a novel slag activation approach based on the synergistic effect of complexation and carbonation, which aims to enhance the resource utilization rate of slag.

Research Progress on Durability of Rubber Concrete

LI Hanjun, SU Haoran, YU Haonan, ZHAO Jing, ZHANG Jiupeng, HU Zhe

2025, 44(1):  180-194.  doi:10.16552/j.cnki.issn1001-1625.2024.1015

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The application of waste tires to concrete preparation is an effective way to realize the resource utilization, recycling of roadside waste as well as low-carbon green construction. In order to further expand the application range of rubber concrete and prolong its service life in complex environments, this paper systematically summarizes and concludes the durability of rubber concrete. Firstly, this paper introduces the common pretreatment methods of rubber particles for the preparation of rubber concrete, then summarizes the effects of rubber particles on its water absorption, dry shrinkage resistance, freeze-thaw resistance, carbonation resistance, chloride ion permeability resistance and corrosion resistance from a macroscopic point of view, and finally explores the role of rubber particles on the durability of concrete from a microscopic point of view. Pretreatment of rubber particles helps to improve the insufficient bonding at the interfacial transition zone between rubber particles and cement matrix in concrete. In addition, the rubber concrete structures show better chloride ion permeability resistance, freeze-thaw resistance, carbonation resistance and corrosion resistance.

Synthesis of Pure Vaterite Regulated by Vitamin C and Its Formation Mechanism

WU Guangwu, BAI Rong, FANG Hu, ZHAO Cheng, CHEN Peiyuan

2025, 44(1):  195-201.  doi:10.16552/j.cnki.issn1001-1625.2024.0824

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In order to establish a process of synthesizing high purity vaterite calcium carbonate with calcium chloride as raw material and storing CO₂, this paper used calcium chloride as calcium source, CO₂ carbonization method and vitamin C as crystal form regulator to control the synthesis of vaterite. The products were characterized by X-ray diffractometer, Fourier transform infrared spectrometer, scanning electron microscope, etc. The effects of different concentrations of vitamin C on calcium carbonate crystals and morphology were studied, and the possible formation mechanism of vaterite under the regulation of vitamin C was discussed. The results show that vitamin C has a significant effect on stabilizing the crystalline form of vaterite. When vitamin C is not added, the product is a mixture of vaterite and calcite, while vaterite with a purity of 100% can be obtained by adding 0.1% (mass fraction) vitamin C. Moreover, with the increase of vitamin C concentration, the specific surface area of calcium carbonate increases from 3.63 m²/g to 11.62 m²/g, and the crystal size decreases from 1~3 μm to 0.3~0.6 μm. This study provides a simple, green, and low-cost method to prepare pure vaterite while safely and effectively sequestering CO₂ greenhouse gases.

Leaching and Kinetics of Aluminum and Silicon from Kaolinite-Rich Coal Gangue

WANG Yangyang, YAO Longfan, DAI Lufei, LI Zhong, MENG Fanhui

2025, 44(1):  202-211.  doi:10.16552/j.cnki.issn1001-1625.2024.0793

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Kaolinite-rich coal gangue contains a large amount of SiO₂ and Al₂O₃. In this work, the coal gangue was selected to leach the Al₂O₃ by using hydrochloric acid and then to leach the SiO₂ from the acid leaching slag by NaOH alkaline. The effects of acid leaching concentration, acid leaching temperature, acid leaching time and liquid-solid ratio on the leaching rate of Al₂O₃ from calcined coal gangue were investigated, and the effects of alkaline leaching conditions on the leaching rate of SiO₂ from acid leaching slag were also explored. The results show that when the conditions of acid leaching and alkali leaching are optimized by single variable experiment, the leaching rate of Al₂O₃ in coal gangue is 92.6%, and the leaching rate of SiO₂ in acid leaching residue is 99.1%. The study of the kinetic models of acid leaching and alkaline leaching processes shows that, the kinetics model of the acid leaching process of coal gangue is in accordance with the mixed control model of internal diffusion and chemical reaction, while the alkaline leaching agreed well with the chemical reaction control model. There is a good linear relationship between the logarithm of the apparent reaction rate constants ln k_c and ln k_b versus T^-1, for the acid leaching mixed control model and the alkaline leaching chemical reaction control model, respectively. In this paper, the kinetic rate equations of acid leaching process and alkali leaching process are also obtained. The results of this study can be used to guide the production of aluminum and silicon leaching from industrial coal gangue.

Influence of Secondary Aluminum Ash Sintered Slag on Mechanical and Shrinkage Properties of High-Strength Concrete

JI Luxin, MA Hongrui, MA Zheyang, WANG Sheng, CUI Jiaming, BA Mingfang

2025, 44(1):  212-222.  doi:10.16552/j.cnki.issn1001-1625.2024.0868

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In order to explore the way of building materials utilization of secondary aluminum ash sintered slag, the influence and mechanism of different content of sintered slag on the mechanical and shrinkage properties of C50, C60 and C70 concrete were studied. The results show that the compressive strength of C50 and C60 concrete is slightly higher than that of unadded sintered slag reference specimen when the content of sintered slag is 15% (account for total fine aggregate mass), while for C70 concrete, the compressive strength of high-strength concrete specimens with different sintered slag content is lower than that of unadded sintered slag reference specimen. When the sintered slag content is in the range of 10%~15%, the reduction of compressive strength is the lowest. The effect of low content sintered slag on peak strain, ultimate strain, elastic modulus and Poisson ratio of high-strength concrete is not obvious, but the effect of high content sintered slag is significant, and the effect is the greatest on higher strength grade concrete. When the sintered slag content is 15%, the total shrinkage rate and self-shrinkage rate of high-strength concrete are the lowest, among which the total shrinkage of C50, C60 and C70 concrete decreases by 29.05%, 22.17% and 27.88%, and the self-shrinkage rate decreases by 15.24%, 26.52% and 30.56%, respectively, compared with the reference group without sintered slag. Therefore, when the content of sintered slag is 15%, the internal curing effect of high-strength concrete is equivalent to the negative effect of low self-strength, so that high-strength concrete can obtain the appropriate compressive strength and the lowest shrinkage rate.

Experimental Study on Hydration Activity Modification of Fluorgypsum

XUE Lutao, LI Yubiao, WU Xiaoyong, LI Rui, SUN Xuchao, WU Kaizhen, CHI Ru’an

2025, 44(1):  223-230.  doi:10.16552/j.cnki.issn1001-1625.2024.0784

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The high acidity and low hydration activity of fluorgypsum restrict its application in the field of plastering gypsum. In order to solve this problem and promote the large-scale application of fluorgypsum in plastering gypsum, CaO and Ca(OH)₂ were selected as neutralizer while Na₂C₂O₄, Na₂SO₄, K₂SO₄, K₂SiO₃ and gypsum hemihydrate were selected as activator, to modify fluorgypsum. The effects of type and dosage of activator and neutralizer on modification effect were investigated. The results show that 3%(mass fraction) neutralizer can improve the pH value of fluorgypsum to around 9 and keep its free fluorine content around 0.02% (mass fraction). Considering the cost, the cheaper CaO is choose as neutralizer. In addition, K₂SO₄, Na₂SO₄ and gypsum hemihydrate as activator have good excitation effect, among which Na₂SO₄ has the best excitation effect. Plastering gypsum excited by 1.0% (mass fraction) Na₂SO₄ is prepared, with initial setting time of 119 min and final setting time of 252 min. Moreover, the compressive strength is 10.30 MPa while the flexural strength is 3.85 MPa. It should be noted that all indicators reach the requirements of “Plastering gypsum”(GB/T 28627—2023).

Effect of Phosphogypsum on Carbonation and Seepage Resistance of Basalt Fiber Concrete

LUO Guoyi, XU Guihong, REN Xu, DENG Wenbo, CHEN Ziwei, LIU Ciqi

2025, 44(1):  231-242.  doi:10.16552/j.cnki.issn1001-1625.2024.0915

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The use of phosphogypsum as a cement-based filling material to replace cementitious materials is an effective comprehensive utilization. At present, there is a lack of systematic research on the internal pore distribution characteristics and the properties of carbonation and seepage resistance of phosphogypsum incorporated into concrete, which can easily lead to structural failure. In this paper, six groups of basalt fiber concrete specimens with different proportions of phosphogypsum content were prepared and tested for carbonation and seepage resistance, and the effect of different phosphogypsum content on the carbonation and seepage resistance of basalt fiber concrete was investigated by combining with XRD, SEM, and specific surface area and pore size analysis. The results show that the carbonation depth of basalt fiber concrete increases with the increase of phosphogypsum content and carbonation age, and there is a functional relationship between phosphogypsum content, carbonation age and carbonation depth. The water penetration height of basalt fiber concrete shows a trend of increasing first and then decreasing with the increase of phosphogypsum content. The microstructural analysis reveals that with the increase of phosphogypsum content, the specific surface area of basalt fiber concrete and pore volume of different pore sizes increase, and the amount of ettringite (AFt) increases. The increase of total pore volume leads to the increase of carbonation rate and water penetration height growth in the early stage. AFt has micro-expansion property, and the joint action of AFt and C-S-H gel to fill up some of the pore channels, which not only lead to the decrease of carbonation rate in the late stage of basalt fiber concrete, and the decrease of water penetration height in the phosphogypsum content more than 6% (mass fraction), but also lead to the decrease of specific surface area and pore volume of different pore sizes of basalt fiber concrete with 15% (mass fraction) phosphogypsum. The research results provide reference information for further enrichment and improvement of phosphogypsum resource utilization technology.

Mechanical Properties and Hydration Mechanism of Chemically Activated High Content Fly Ash Composite Cementitious Materials

DOU Zhanshuang, LI Xiaomin, QIN Hongtao, WEI Dingbang, WU Xu, YAN Sheng, ZHANG Fuqiang, HAN Fangyuan

2025, 44(1):  243-252.  doi:10.16552/j.cnki.issn1001-1625.2024.1007

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In this study, a high content fly ash (m(slag powder)∶m(fly ash)=1∶3 (mass ratio)) was used as matrix, and the composite activators under different compounding methods were obtained by orthogonal test design. The effects of different single-doped and co-doped activators on the mechanical properties and hydration mechanism of high content fly ash cementitious system were studied by XRD, FT-IR, TG-DTG, SEM and other test methods. The results show that Na₂SiO₃ has the best activation effect on the high content fly ash composite cementitious system in the single-doped activator. When Na₂SiO₂ content is 1.0% (mass fraction), 7 and 28 d compressive strength of high content fly ash composite cementitious system is 17.5 and 31.7 MPa, respectively. The optimal mass ratio of multiple activators to the excitation effect of high content fly ash cementitious system is m(slag powder)∶m(fly ash)=1∶3. The compressive strength of 7 and 14 d is 27.5 and 35.5 MPa, respectively. The compressive strength of 28 d is increased to 49.2 MPa, reaching the strength index of 42.5 cement. This is due to the secondary pozzolanic reaction of the active substances of fly ash in alkaline environment, and the hydration products such as AFt and C-(A)-S-H gradually increase, which significantly enhances the compressive strength of the cementitious material. This study not only provides a new way for the high-content utilization of fly ash, but also provides a reference for the research and development of solid waste composite materials.

Mechanical Properties and Microstructure of Recycled Brick Powder ECC after Physical Excitation

CHU Liusheng, DU Feixiang, TIAN Ye, YUAN Chengfang, CHENG Zhanqi

2025, 44(1):  253-263.  doi:10.16552/j.cnki.issn1001-1625.2024.0812

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The waste clay brick contains a large amount of active mineral components such as SiO₂ and Al₂O₃. After crushing and grinding, recycled brick powder (RBP) can be prepared. By improving the pozzolanic activity of RBP through effective excitation methods, RBP can be applied to engineered cementitious composite (ECC) as part of cementitious materials, which has great economic and environmental benefits. By analyzing the activity index, microstructure and XRD pattern of RBP after physical excitation, the optimum physical excitation time of RBP was determined. On this basis, the recycled brick powder-engineered cementitious composite (RBP-ECC) was prepared with RBP after active excitation. The flexural, compressive, uniaxial tensile and four-point bending tests were carried out to study the influence of RBP replacement rate on the mechanical properties of RBP-ECC. The results show that the strength indexes of RBP-ECC decrease with the increase of RBP replacement rate after physical excitation, while the ultimate tensile strain and mid-span deflection increase gradually, up to 5.22% and 55.53 mm, respectively. When the RBP replacement rate is 20% (mass fraction), the bending toughness index of RBP-ECC increases the most, which is about 59% higher than that of benchmark ECC. Each strength index of RBP-ECC has a lower decline, but still can maintain high strength and toughness. The strength, toughness and sustainability indexes of RBP-ECC were comprehensively considered, and 20% was selected as the best brick powder replacement rate of RBP-ECC, and microscopic analysis of RBP-ECC fiber-matrix interface under this replacement rate was carried out. The results show that there are fiber pull-out failure modes and fiber breaking failure modes in RBP-ECC at 20% RBP replacement rate, and RBP-ECC shows higher tensile toughness and suitable tensile strength compared with benchmark ECC.

Mechanical Properties of Steel Fiber Reinforced Self-Compacting Concrete with Recycled Aggregate

YU Fang, LI Linbo, YAO Dali

2025, 44(1):  264-273.  doi:10.16552/j.cnki.issn1001-1625.2024.0787

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Self-compacting concrete with recycled aggregate (RASCC) with 100% (mass fraction) recycled aggregate (RA) is an environmentally friendly and green building material with high workability, which limits its engineering application due to its lower strength than pure natural concrete. The mechanical properties of RASCC were improved by incorporating steel fiber, and compressive, split tensile and flexural tests were carried out to investigate the optimum steel fiber volume fraction V_f and length-to-diameter ratio L_f/d_f, and to compare the mechanical properties of RASCC under different RA replacement rates at the optimum V_f and L_f/d_f. The results show that the effects of V_f and L_f/d_f on the flowability of steel fiber reinforced self-compacting concrete with recycled aggregate (SFRASCC) are greater than those of RA substitution rate. Compared with RASCC without steel fiber, the best enhancement of cubic compressive strength is achieved at 0.25% V_f, which increases by 20.9%, whereas the best enhancement of split tensile strength and flexural strength is achieved at 0.50% V_f, which increases by 50.0% and 58.3%, respectively. Compared with the RASCC without steel fiber, the best improvement in cubic compressive strength is achieved when L_f/d_f is 33.3, while the best improvement in split tensile strength and flexural strength is achieved when L_f/d_f is 63.6. In the case of steel fiber volume fraction and appropriate aspect ratio, it is feasible to use 30% RA or 100% RA to replace the natural aggregate, but it is more environmentally friendly to use the replacement rate of 100% RA. The established formulae for the compressive strength and split tensile strength of SFRASCC cubes can be used for reference.

3D Percolation Performance of Recycled Aggregate Concrete in Real Marine Exposure Environments

ZHU Yuanlang, ZHANG Mingliang, WEI Jinghua, ZHANG Hengwu, LIU Zipan, GAO Song

2025, 44(1):  274-288.  doi:10.16552/j.cnki.issn1001-1625.2024.0897

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To elucidate the dynamic evolution of pore structure characteristics in recycled aggregate concrete (RAC) under real marine exposure environments, this study integrated percolation theory with advanced micro-testing techniques, including X-ray computed tomography (X-CT), alongside macro-performance analyses. The investigation focused on the pore distribution and chloride ion corrosion in RAC modified with fly ash (FA) and metakaolin (MK) subjected to real marine exposure. The study provided a comprehensive assessment of the effect of chloride ion corrosion on the progression and development of internal pores and cracks within RAC, and examined the percolation performance across various RAC formulations and real marine exposure ages. Findings reveal that the strategic incorporation of FA and MK significantly improves RAC compressive strength and resistance to chloride ion corrosion. A discernible correlation between fractal dimension and both macro-performance and percolation parameters is established. Percolation theory effectively predicts chloride salt migration and elucidates the underlying erosion mechanisms. This research offers critical insights into ion transport mechanisms in concrete and enhances the understanding of RAC durability.

Effect of Carbonated Recycled Concrete Powder on Alkali-Activated Slag Materials

LI Qi, WANG Liang, WANG Hao, WANG Chenglong, XU Jian, HU Wei

2025, 44(1):  289-296.  doi:10.16552/j.cnki.issn1001-1625.2024.0818

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In order to promote the application of recycled concrete powder (RCP) in alkali-activated slag (AAS) materials, this paper uses carbonization technology to improve the quality of RCP and replaces 10%~40% (mass fraction, the same below) granulated blast furnace slag (GBFS) with RCP to prepare AAS mortar. The effect of the dosage of carbonated recycled concrete powder (CRCP) on the hydration performance, mechanical strength, and microstructure of AAS mortar was investigated. The results show that main components of CRCP are fine-sized calcium carbonate and silica gel, which have high water absorption and can reduce the fluidity of AAS mortar. CRCP can promote hydration of GBFS by filling and activity effects, improving the packing density and pore structure of AAS mortar, thereby increasing compressive strength. It is observed that when CRCP content reaches 20%, the resulting AAS mortar exhibits an optimal compressive strength approximately 16%~20% higher than that achieved with non-carbonated RCP.

Effect of Calcium Silicon Ratio on Sintering Behavior and Carbon Sequestration Capacity of Calcium Silicate Mineral Phase

CHEN Ping, LI Fangbin, XIANG Weiheng, HU Cheng, LIU Jun, WANG Qijie

2025, 44(1):  297-304.  doi:10.16552/j.cnki.issn1001-1625.2024.0797

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Calcium silicate carbonatable binder is an important direction to realize the green and sustainable development of building materials industry. In order to study the effect of calcium silicon ratio (n(CaO)∶n(SiO₂), molar ratio) on the composition of calcium silicate mineral phase and their carbon sequestration capabilities, calcium silicate carbonatable binders were synthesized with controlled calcium silicon ratio (n(CaO)∶n(SiO₂)=1.8~2.2). Techniques such as t-pH, XRD, TGA, and SEM were employed to examine the evolution of phase composition, carbonization hardening process, CO₂ uptakes and carbonization products of calcium silicate carbonatable binders. The results indicate that the content of γ-dicalcium silicate (Ca₂SiO₄, γ-C₂S) initially increases and subsequently decreases as the calcium silicon ratio rises. When the calcium silicon ratio is no higher than 2.0, the content of rankinite (Ca₃Si₂O₇, C₃S₂) gradually increases with the decreasing of calcium silicon ratio. When the calcium silicon ratio is higher than 2.0, the content of β-dicalcium silicate (Ca₂SiO₄, β-C₂S) progressively increases with the increasing of calcium silicon ratio. The reaction of carbonization for 0.5 h is intense, and the compressive strength initial increases and subsequent decreases as the calcium silicon ratio increases. The reaction produces calcite, aragonite and vaterite. With the content of C₃S₂ and γ-C₂S decreasing significantly, and the calcite content remains largely unchanged even when the carbonization reaction is extended to 24 h. C₃S₂ decelerates the early reaction of binder, but a more sustained carbonization reaction and a greater variety of carbonization products can enhance its subsequent compressive strength. The compressive strength and CO₂ uptakes after carbonization for 24 h reach 129.76 MPa and 18.57%, respectively.

Ceramics

Research Progress on Low Temperature Synthesis Method of Magnesium Niobate Powder

TONG Yaqi, ZHANG Wei , LI Hui, ZHENG Yu, ZHANG Jie, SHI Shuangshuang

2025, 44(1):  305-311.  doi:10.16552/j.cnki.issn1001-1625.2024.0759

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Magnesium niobate microwave dielectric ceramics have attracted much attention because of their excellent dielectric properties. Magnesium niobate powder is a crucial raw material for preparing high-performance magnesium niobate ceramics, the quality of which plays a vital role in the performance of final product. In this paper, the current preparation methods of magnesium niobate powder at home and abroad are systematically summarized, the advantages and limitations of solid state reaction method, wet chemical method,co-precipitation method and sol-gel method are analyzed, and the future development direction of magnesium niobate powder preparation technology is prospeced, which provides useful reference and enlightenment for the research and development of high-performance magnesium niobate powder materials.

Durability Evaluation and Application Scenario Analysis of Sealing Materials for Qianling Green Glaze Tang Tri-Color

SHI Pei, CHEN Le, JIA Weiming, ZHEN Gang, MA Tao, ZHANG Xin, WANG Fen, ZHU Jianfeng, ZHANG Biao

2025, 44(1):  312-320.  doi:10.16552/j.cnki.issn1001-1625.2024.0821

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In this study, 10% (mass fraction) acrylic resin (Paraloid B67, Paraloid B72), fluorocarbon resin (FEVE) and silicone material (WD-10) were used to seal the glaze surface of Qianling green glaze Tang tri-color replica. The color difference, hydrophobicity, ultraviolet (UV) aging resistance, salt spray aging resistance and acid corrosion resistance of different sealing materials were compared and studied by chromaticity meter, video optical contact angle tester, ultraviolet-visible spectrophotometer, infrared spectrometer and super depth of field microscope, and their application scenarios were analyzed. The results show that Paraloid B67 exhibits good color difference and hydrophobicity in the early stage of UV aging, but its performance decreases significantly with the extension of UV aging time, and its acid corrosion resistance and salt spray aging resistance are general, which is suitable for the sealing of indoor glazed pottery cultural relics in humid climate. Paraloid B72 is similar to Paraloid B67 in UV aging performance, but its acid corrosion resistance and salt spray aging resistance are the best, which is suitable for indoor glazed pottery cultural relics protection in complex environments. FEVE performs poorly in acid corrosion resistance and salt spray aging resistance, but the color difference and hydrophobicity change range before and after ultraviolet aging are the smallest, and the anti-ultraviolet aging performance is the best, which is suitable for outdoor glazed pottery cultural relics in areas with stable climate and environment. WD-10 is difficult to form a film on the glaze surface of the replica, which is not suitable for the sealing of glazed pottery relics.

Refractory Materials

Preparation and Properties of Mullite Whisker Reinforced Aluminum Silicate Fiber Composites

MA Xiaoliang, WANG Guigen, ZHANG Mengyu, ZHAO Baojun, ZHONG Yesheng, SHI Liping, HE Xiaodong

2025, 44(1):  321-331.  doi:10.16552/j.cnki.issn1001-1625.2024.0779

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In this paper, a non-toxic and low-energy-consuming process for in-situ growth of mullite whiskers on the surface of aluminum silicate fiber was developed. Firstly, the thermophysical properties and morphology of mullite whisker reinforced aluminum silicate fiber composites were characterized, and the optimum heat treatment temperature for in-situ growth of mullite whiskers under borax fluxing was determined. Then, under the optimum heat treatment temperature, silica sol and aluminum nitrate were used as silicon source and aluminum source respectively, and borax was used as flux. The effects of flux concentration and holding time on whisker morphology, phase composition, density and compressive strength were analyzed. The results show that mullite whiskers with “thin needle shape” are successfully grown on the surface of aluminum silicate fiber under borax fluxing. The optimum conditions are as follows: heat treatment temperature 900 ℃, holding time 2 h, flux concentration 0.17 mol/L, silica sol concentration 0.17 mol/L, aluminum nitrate concentration 0.51 mol/L. The compressive deformation of mullite whisker reinforced aluminum silicate fiber can reach up to 60%, and the compression strength of this material can reach up to 0.462 MPa at 60% compression deformation.

Preparation and Performance Optimization of Aerogel-Porous Zeolite Composite Loaded Inorganic Composite Polystyrene Insulation Board

ZHANG Weiyi, LUO Jianlin, WU Dagang, WANG Chunzeng, SHANG Huaishuai, LIU Zhijun

2025, 44(1):  332-342.  doi:10.16552/j.cnki.issn1001-1625.2024.0772

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Under the background of energy saving, emission reduction and "double carbon" target, it is urgent to develop a type of inorganic composite polystyrene A class thermal insulation board integrated with diversified functions. Aerogels and porous zeolites possess porous structural characteristics and are excellent materials with low thermal conductivity coefficient. In this paper, aerogel-porous zeolite composite was firstly synthesized, and the influences of different dosages of EPS particles, aerogel-porous zeolite composite and modifying agent on the dry density, thermal conductivity, mechanical strength, fire prevention and waterproof performance of aerogel-porous zeolite composite loaded inorganic composite polystyrene insulation board (AIPIB) were comprehensively studied. AIPIB with dry density of 152 kg/m³, thermal conductivity coefficient of lower than 0.050 W/(m·K), combustion performance of class A, 14 d compressive strength of higher than 0.15 MPa, 7 d saturation absorption of less than 5% is achieved, and the interface bonding of AIPIB is good. Compared with the performance of the A class thermal insulation board specified in “Thermal composite polystyrene foam insulation board” (JG/T 536—2017), AIPIB has lower thermal conductivity coefficient, higher compressive strength, better waterproof and fire prevention performance, and the bonding performance between inorganic and organic component is good with outstanding comprehensive advantages.

Effect of Y₂O₃/ZrO₂ on Properties of MgO-CaO Refractory

JIN Hulin, MA Yan, WANG Zhoufu, DENG Chengji, WANG Xitang, LIU Hao, DONG Yunjie, TONG Guangda, FU Weidong

2025, 44(1):  343-352.  doi:10.16552/j.cnki.issn1001-1625.2024.0878

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MgO-CaO refractories have a broad application prospect as furnace lining materials for clean steel and special steel smelting due to their good high temperature resistance and ability to purify steel. However, these materials still have problems such as difficult sintering, easy hydration and mechanical properties need to be improved. In this work, Y₂O₃/ZrO₂ co-doped MgO-CaO refractories were prepared by comparing with Y₂O₃ and ZrO₂ single-doped MgO-CaO refractories. The effect of Y₂O₃/ZrO₂ introduction on the microstructure and properties of materials was investigated. The results show that some Y₂O₃ dissolves into the CaO lattice, while other Y₂O₃ locates at the intergranular region in the Y₂O₃ single-doped MgO-CaO materials. The intergranular Y₂O₃ hinders the sintering of the material. When a small amount of ZrO₂ is synergistically introduced, the density of the material increases, and the room temperature flexural strength and hydration resistance are improved. This is due to the in-situ generated CaZrO₃ filling in the voids, which is favourable to the sintering properties of the materials. However, when excessive ZrO₂ is introduced, more CaZrO₃ generates in the materials, and the significant volume expansion leads to the increase of apparent porosity, leading to a decrease in the mechanical properties and hydration resistance of the materials.

Functional Materials

Luminescence Properties and Energy Transfer of Y₂MgTiO₆∶Dy³⁺,Eu³⁺ Phosphors

JIANG Xiaokang, GAO Feng, ZHOU Hengwei

2025, 44(1):  353-359.  doi:10.16552/j.cnki.issn1001-1625.2024.0701

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A series of Y_2(0.97-x)Dy_0.06MgTiO₆∶2xEu³⁺(YMT∶0.06Dy³⁺,2xEu³⁺) phosphors were successfully synthesized by sol-gel method. The effect of Dy³⁺, Eu³⁺ co-doping on phase, microstructure and fluorescence properties of samples was investigated. The results show that the prepared YMT∶0.06Dy³⁺,2xEu³⁺ phosphors are double perovskite structure (crystallized in monoclinic space group P2₁/n) and the particle size is 1~2 μm. Under the excitation of 262 nm ultraviolet light, the emission spectra show a typical linear characteristic spectra of Dy³⁺ and Eu³⁺. The main emission peaks are located at 483(⁴F_9/2→⁶H_15/2), 579(⁴F_9/2→⁶H_13/2) and 619 nm (⁵D₀→⁷F₂), respectively. There is a significant energy transfer between Dy³⁺and Eu³⁺, which is mediated by electric dipole-electric dipole (d-d) interaction. The luminescence intensity of the obtained phosphors at 423 K could remain 74.36% of that at room temperature, showing excellent thermal stability. By changing the concentration of Eu³⁺, the luminescence color of phosphors shift from yellow region to orange-red spectral region. YMT∶0.06Dy³⁺,2xEu³⁺ phosphors are expected to be candidate materials for solid-state LED lighting.

Road Materials

Influence of Raw Soil Liquid Limit on Engineering Properties of Self-Compacting Solidified Soil

XU Jie, LIANG Jianhui, QI Le, GONG Ying, GAO Yufeng

2025, 44(1):  360-367.  doi:10.16552/j.cnki.issn1001-1625.2024.0769

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Self-compacting solidified soil has been extensively utilized in various backfilling projects due to its advantages such as on-site soil extraction, synergistic disposal of construction waste, self-leveling, and pumpability. This study investigated the influence of liquid limit of raw soil on the engineering properties of self-compacting solidified soil through a series of tests including fluidity, bleeding rate, wet density, drying shrinkage, and unconfined compressive strength tests, complemented by free water separation tests to further explore the role of free water content in strength characteristics. The results demonstrate that under identical cement content and water-to-soil ratio, the freshly mixed slurry of self-compacting solidified soil made from high liquid limit clay exhibits lower fluidity but higher unconfined compressive strength after curing. With an increase in the water-to-soil ratio, the increment in fluidity of the freshly mixed slurry remains relatively constant, while the reduction in unconfined compressive strength after curing begins to diminish. Regardless of the curing age, the content of free water in self-compacting solidified soil made from high liquid limit clay is consistently lower. At a curing age of 7 d, the free water content in self-compacting solidified soil made from high liquid limit clay is only 2.2%, compared to 11.7% in samples made from low liquid limit clay. This research unveils the mechanism by which different liquid limits of raw soil affect the free water content in self-compacting solidified soil, offering scientific guidance for the selection of raw soil and the design of its mix proportion in engineering applications.

Mix Ratio Optimization Research on Composite Cured Soil Based on Response Surface Method

ZHANG Kunpeng, ZHANG Ning, DING Beidou

2025, 44(1):  368-377.  doi:10.16552/j.cnki.issn1001-1625.2024.0720

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In order to improve the poor grading, loose overall structure and low strength of silt as subgrade material, the composite curing agent was prepared with red mud (RM), carbide slag (CS) and desulphurized gypsum (DG) as raw materials, and the mix ratio optimization of composite cured soil was carried out in this paper. The reasonable content range of red mud, carbide slag and desulfurized gypsum cured soil was determined by single factor test, and the mix ratio of composite cured soil was optimized by Box-Behnhen response surface method. A second-order regression model was established with 7 and 28 d unconfined compressive strength (UCS) as response values. The results show that the significant degree of influence of single factor on the unconfined compressive strength of cured soil at 7 and 28 d is carbide slag, red mud and desulphurized gypsum. The influences of two factors on the unconfined compressive strength of cured soil at 7 d is in the order of red mud and carbide slag, red mud and desulphurized gypsum, carbide slag and desulphurized gypsum, and the influence on the unconfined compressive strength at 28 d is in the order of red mud and carbide slag, carbide slag desulphurized gypsum, red mud and desulphurized gypsum. The optimal mix ratio of composite cured soil is 15.84% (mass fraction) red mud, 14.32% (mass fraction) carbide slag and 7.32% (mass fraction) desulphurized gypsum. The error range of the measured and predicted response values is controlled within 3%, which proves the accuracy and scientificity of the response surface method in optimizing the mix ratio of composite cured soil. The main products of cured soil are calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) with gelling effect, and the resulting ettringite (AFt) is interspersed between the gel and soil particles to enhance the strength of soil.

Study on High Efficiency Particle Size Range of Biological Enzyme-Directed Action on Red Sandstone Soil

GUAN Hongxin, ZHENG Tianyi, ZHANG Haixiang, YANG Fei, YANG Hairong, PAN Wang, LI Huili

2025, 44(1):  378-387.  doi:10.16552/j.cnki.issn1001-1625.2024.1061

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In order to enhance the solidification effect of biological enzymes on red sandstone soil more efficiently, the process of preparing test specimens was optimized in the laboratory, which involved screening the red sandstone soil into a target particle size range (P_≤2.36, P_2.36~4.75, P_≥4.75), and directing the biological enzyme to act on the red sandstone soil in the target particle size range. Unconfined compressive strength, static compressive elastic modulus, splitting strength and erosion resistance tests were conducted on biological enzyme cement composite solidified red sandstone soil specimens. In addition, in order to further study the influencing factors of biological enzyme-directed action, SEM tests were carried out on different proportions of soil with particle size below 0.075 mm accounting for the total mass of particles with particle size below 2.36 mm and below. The test results show that a particle size below 2.36 mm is the highly efficient particle size range for biological enzyme cement composite solidified red sandstone soil. Compared with the conventional method of adding biological enzyme to the specimen, the highly efficient particle size of biological enzyme-directed action on red sandstone soil can further improve the unconfined compressive strength, splitting strength and static compression elastic modulus of the specimen, and significantly reduce the quality loss of erosion. The microscopic test results show that the content of clay material has a significant impact on the solidification effect of biological enzyme, and the proportion of particle size below 0.075 mm has a significant impact on the surface morphology of the soil. It is suggested that the biological enzyme be applied to solidify red sandstone soil by improving its construction technology, so that the biological enzyme is only used on soil particles below 2.36 mm.