Table of Content

15 June 2024, Volume 43 Issue 6

Previous Issue    Next Issue

Cement and Concrete

Effect of Low Humidity and Varying Temperature Environment on Performance of Cement under Sulfate Attack

JIA Yantao, LI Zhiheng, WANG Dafu, WU Meng

2024, 43(6):  1965-1974. 

Asbtract ( 223 )   PDF (12856KB) ( 163 )  

References | Related Articles | Metrics

Based on environmental characteristics of reinforced concrete infrastructure in western China, cement mortar specimens were subjected to semi-immersed sulfate corrosion in low humidity and varying temperature. The influences of low humidity and varying temperature on semi-immersion sulfate attack cement-based materials were studied by combination of XRD, SEM, LF-NMR, and conductivity titration of sulfate ions. The results show that under low humidity and varying temperature, the mortar subjected to semi-immersion sulfate attack has a water film zone within 30 mm above the surface of sulfate solution, and the corrosion degree is relatively low. The evaporation zone above the solution surface of 30~60 mm has a higher degree of corrosion and obvious peeling phenomenon. Corrosion of evaporation zone of mortar semi-immersed in Na₂SO₄ solution is more seriously than that semi-immersed in MgSO₄ solution due to their difference in saturation under different temperatures. The expansive salt crystallization within pores above 1 000 nm is prone to the occurrence in evaporation zone, which leads to the micro cracks inside mortar and an increase in the proportion of harmful pores, resulting in physical expansion damage being the main cause of this zone. Chemical corrosion in the immersion zone of mortar is dominant due to the formation of swelling corrosion products such as gypsum and ettringite. As corrosion products accumulated in the pores with pore sizes of 50~1 000 nm, the surface of mortar cracks and the proportion of macroscopic pores with pore sizes above 1 000 nm increases. The addition of ground granulated blast furnace slag in cement increases the sulfate corrosion resistance of the immersion zone of mortar via its secondary hydration effect, and the addition of limestone powder decreases the sulfate corrosion resistance of mortar due to its dilution effect.

Effect of Silica Fume Heat-Welded Modified Plastic Particles on Compressive Strength and Microstructure of Mortar

WANG Xianggeng, CHEN Peiyuan, LI Jin, ZHAO Cheng, GU Zhicheng

2024, 43(6):  1975-1982. 

Asbtract ( 74 )   PDF (8958KB) ( 31 )  

References | Related Articles | Metrics

In order to address the issue of reduced compressive strength in plastic mortar caused by the hydrophobic nature of plastic, this study utilizes the thermoplasticity of discarded polypropylene (PP) plastic to prepare silica fume@plastic particle composite particles (SF@PP) by welding silica fume on the surface of PP through the thermal welding process and tests the hydrophilicity and volcanic ash activity of the composite particles. The results indicate that the modified plastic through silica fume heat welding improves the hydrophilicity of PP and enhances its volcanic ash activity, promoting the deposition of hydration products at the interface and increasing the compactness of the interface. Consequently, the porosity of the plastic mortar is significantly reduced, and the compressive strength is significantly increased by 26.07% to 31.04%. The results of the study are conducive to the efficient utilization of waste plastics and provide a basis for the preparation of high-performance plastic mortar.

Effects of Curing Methods on Hydration-Hardening Performance of Reactive MgO Cement

WANG Huanhuan, CAI Tongzhou, HOU Pengkun

2024, 43(6):  1983-1991. 

Asbtract ( 84 )   PDF (18907KB) ( 48 )  

References | Related Articles | Metrics

Reactive MgO cement (RMC), which undergoes hardening through the reaction of MgO with water and CO₂, is a novel cementitious material that has gained significant attention in recent years. The hydration and carbonation processes of RMC samples are significantly affected by the curing method and water content. This work compared the effects of standard curing ((20±1) ℃, 95% relative humidity), water curing ((20±1) ℃), and carbonation curing ((20±3) ℃, 70% relative humidity, 20% (volume fraction) CO₂) on the properties of RMC with water-cement ratio (w/c) of 0.5, 0.6, and 0.7, respectively. The types and content of the phases of the hydration and carbonation reaction products as well as their micro-morphological characteristics were investigated. The results show that the residual content of MgO in samples is 10%~15% (mass fraction) at 3 d and disappears at 14 d under standard curing and water curing. When w/c is 0.6, the compressive strength of paste reaches 7.7 and 3.2 MPa at 14 d under standard curing and water curing, respectively. The strength of paste under carbonation curing is superior to that under standard curing and water curing (3 d compressive strength, 16.19, 0.42, and 0.43 MPa, 14 d compressive strength, 22.34, 7.46 and 7.23 MPa). The quantitative analysis results show that the carbonation product is mainly MgCO₃·3H₂O. When w/c is 0.6, the content of MgCO₃·3H₂O is 12.12% and 11.29% higher than that of samples with w/c=0.5 and 0.7. The main reason for the optimal compressive strength could lies in that these needle-rod MgCO₃·3H₂O are bonded to each other form a dense microstructure.

Characteristics of Interfacial Transition Zone in Manufactured Sand Mortar

CHEN Hao, WANG Huaizhi, WANG Peng, XIAO Min, WU Juan, TANG Yanfeng, LI Fangxian, WEI Jiangxiong

2024, 43(6):  1992-1998. 

Asbtract ( 111 )   PDF (12580KB) ( 129 )  

References | Related Articles | Metrics

The study of interfacial transition zone characteristics in manufactured sand mortar is of great significance in enhancing the strength and durability of manufactured sand mortar. The interface microstructure, microzone mechanical strength, and non-uniform deformation of mortar composed of river sand and manufactured sand were examined through scanning electron microscopy (SEM), nanoindentation, and three-dimensional digital image correlation (3D-DIC) techniques. The results indicate that the width of the interfacial transition zone in manufactured sand mortar exceeds that in river sand mortar. Nevertheless, the interface cracks between fine aggregate particles and mortar matrix are smaller in manufactured sand mortar. Notably, microcracks are prone to occurring at the edges of manufactured sand particles. The elastic modulus of the interfacial transition zone in manufactured sand is slightly higher than that in river sand, suggesting that manufactured sand can mitigate the edge effect of aggregates to a certain extent. The non-uniformity of shrinkage deformation is most conspicuous in sandstone manufactured sand mortar, displaying larger internal tensile strains, ultimately leading to a more severe distribution of damage. This implies that an excessive proportion of blade-shaped particles in fine aggregates may heighten the risk of cracking in mortar.

Influence and Mechanism Analysis of Re-Dispersible Latex Powder on Performance of Steel Structure Interface Mortar

WANG Xiaoyan, YE Wuping, CAO Liqiang

2024, 43(6):  1999-2004. 

Asbtract ( 56 )   PDF (5865KB) ( 29 )  

References | Related Articles | Metrics

Re-dispersible latex powder is the key material for the preparation of steel structure interface mortar. In this paper, the influence of the content of re-dispersible latex powder on the 28 d compressive strength, flexural strength and tensile bond strength of interfacial mortar was researched. At the same time, combined with scanning electron microscopy, X-ray spectroscopy and other microscopic analysis methods, the bonding mechanism of re-dispersible latex powder to enhance the interfacial mortar was analyzed. The results show that the suitable content of re-dispersible latex powder is 15% (mass fraction, same below) in the preparation of steel structure interface mortar. Under the appropriate dosage, the tensile bond strength of the interface mortar reaches 1.12 MPa, and thecompressive-flexural strength ratio is 2.3. The addition of latex powder can effectively improve the flexibility of the mortar. The addition of latex powder changes the pore structure of the mortar, and the porosity becomes larger. The hydration products in interfacial transition zone are mainly polymer film encapsulated hydration products C-S-H gel and Ca(OH)₂.

Effect of Aluminum Sulfate Base Alkali-Free Liquid Accelerating Agent Modified by Fluorine Silicon Slag on Cement Properties

LIU Yuan, LIU Xiaotong, YANG Anxu, ZHANG Yuanyong, YANG Lin

2024, 43(6):  2005-2011. 

Asbtract ( 68 )   PDF (7008KB) ( 51 )  

References | Related Articles | Metrics

In this paper, the aluminum sulfate based alkali-free liquid accelerating agent was modified by fluorine silicon slag, and the performance index of alkali-free liquid accelerating agent modified by fluorine silicon slag was tested. XRD, TG-DTG and SEM were used to explore the action mechanism of aluminum sulfate base alkali-free liquid accelerating agent modified by fluorine silicon slag on cement hydration process. The results show that with the increase of fluorine silicon slag content, the rapid setting effect and strength of mortar increase first and then decrease. When the alkali-free liquid accelerating agent is modified by fluorine silicon slag, the appropriate content of fluorine silicon slag is 5.0% (mass fraction). At this time, the initial setting time is 1 min 20 s, the final setting time is 5 min 20 s, 1 d compressive strength is 13.8 MPa, and 28 d compressive strength is 52.4 MPa. Calcium silicate hydrate is formed by the reaction of silica in fluorine silicon slag and cement hydration product calcium hydroxide, which is beneficial to improve the early strength of cement. However, the process of cement hydration and hardening process is hindered by the reaction of fluorine and calcium hydroxide to produce a large amount of calcium fluoride precipitation.

Crack Repairability of Cementitious Materials by Superabsorbent Polymers in Different Environmental Solutions

YANG Shijie, ZHANG Shiping, NIU Longlong, ZHANG Shouwei

2024, 43(6):  2012-2021. 

Asbtract ( 83 )   PDF (10804KB) ( 39 )  

References | Related Articles | Metrics

Cracking and repair of concrete have always been the focus of attention in engineering field. Superabsorbent polymers (SAP) have a certain crack self-healing function. In this paper, the liquid absorption properties of SAP under different environmental solutions (NaOH, NaCl and distilled water) were tested. The compressive strength recovery rate of cracked specimens, the self-healing rate of different crack widths (0.1, 0.2 mm ) and the crack filling state were used as repair indicators. The repair effect of SAP with different mass fractions (0%, 0.5%, 1.0%) on cracked mortar specimens under different environmental solutions was analyzed. The results show that the liquid absorption rate of SAP in different environmental solutions increases rapidly and then tends to be stable, and the liquid absorption rate of SAP in NaOH environmental solution is the highest. The incorporation of SAP improves the compressive strength recovery rate of cracked mortar specimens under different environmental solutions to a certain extent. Among them, the compressive strength recovery rate of specimens mixed with 0.5% SAP in NaOH environmental solution for 28 d is the highest, which is 17% higher than that of reference group. The incorporation of SAP improves the self-healing properties of mortar specimens with different crack widths in different environmental solutions. With the increase of SAP content, the self-healing properties of mortar specimens with 0.2 mm crack width repaired in NaOH environmental solution for 28 d is significantly higher than that of distilled water and NaCl solution. The self-healing rate of specimens with 1.0% SAP in NaOH environmental solution is 90%. The incorporation of SAP cooperates with hydration products to seal the crack mouth, so it is beneficial to improve the durability of cement mortar.

Evolution Rule of Dynamic Mechanical Properties of Cement-Based Materials Containing SAP

LI Jianfeng

2024, 43(6):  2022-2030. 

Asbtract ( 79 )   PDF (7647KB) ( 47 )  

References | Related Articles | Metrics

There is less research on the mechanical behavior ofcement-based materials containing superabsorbent polymers (SAP) under high strain rate. In this paper, the total porosity and macroscopic pore (>100 μm) porosity of cement-based materials containing SAP were investigated by the use of mercury intrusion and graphical techniques. The effects of SAP particle size and extra water on the quasi-static (10^-5 s^-1) and dynamic (60~110 s^-1) mechanical properties of the modified materials were analysed. Based on the study of the crack propagation behavior, the damage behavior of the cement-based materials was analyzed under high strain rates. The results show that the addition of extra water and the increase of SAP particle size improve the total porosity and macroscopic pore porosity of the materials, which reduce the compressive strength and elastic modulus of the specimens under quasi-static and dynamic compression. The addition of extra water and the increase of SAP particle size also enlarge the compressive strength dynamic increase factor and elastic modulus dynamic increase factor of the cement-based materials, which is due to the fact that an increase in total porosity and macroscopic pore porosity induces a change in the crack extension path, an increase in fragmentation, and a delay in the strain response.

Superhydrophobic Biomimetic Construction and Microscopic Mechanism of Hydraulic Concrete

WANG Bo, QIAN Jun, LUO Jie, XU Yi, CHU Hongqiang, JIANG Linhua

2024, 43(6):  2031-2038. 

Asbtract ( 90 )   PDF (6796KB) ( 68 )  

References | Related Articles | Metrics

The organic isooctyltriethoxysilane (TS) and inorganic nanosilicon dioxide (nano-SiO₂) were combined to prepare monolithic superhydrophobic hydraulic concrete by "binary synergistic" biomimetic method, and the effects of TS dosage and curing conditions on the mechanical properties and hydrophobicity properties of concrete were investigated. The microscopic morphology, phase composition and hydrophobic modification mechanism of materials were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transform infrared spectrometer (FT-IR). The results show that the curing conditions have a large influence on the hydrophobicity of concrete. Under natural curing conditions, when TS dosage reaches 3% (mass fraction), the concrete all exhibits superhydrophobicity, with a maximum contact angle of 155.6°. The incorporation of nanoparticles promotes cement hydration and enhances compressive strength of specimens. The modified hydraulic concrete has good hydrophobicity, and the water absorption rate decreases by 68.8% in 288 h immersion.

Effect of Magnetized Water on Mechanical Properties and Durability of Marine Concrete

ZHENG Biao, LI Shunkai, LI Yulin, SU Youliang, LIN Yian

2024, 43(6):  2039-2046. 

Asbtract ( 64 )   PDF (5232KB) ( 26 )  

References | Related Articles | Metrics

In order to deal with the problem that the marine concrete with large dosage of mineral admixture in the actual project faces the harsh marine environment prematurely and is easy to be eroded by chlorine salt, this paper proposed to use magnetized water instead of tap water to prepare marine concrete, studied the influence law of magnetized water on the mechanical properties and durability of marine concrete at different ages, and analyzed the microstructure of marine concrete using the mercury instrusion porosimetry and scanning electron microscope. The study shows that magnetized water improves the workability of marine concrete. Compared with tap water, magnetized water has obvious improvement on the early mechanical properties of marine concrete, in which the compressive strength and splitting tensile strength of C50 marine concrete with a curing age of 7 d increase by 17.9% and 16.5%, respectively. Regardless of different curing ages, the resistance to carbonation and chloride ion penetration of magnetized water marine concrete are better than tap water marine concrete. The degree of reaction of cementitious materials in magnetized water marine concrete is higher, with fewer cracks, and the microstructure between cementitious materials and aggregates is more compact. The overall porosity is lower, with more harmless pores and fewer harmful pores, leading to a denser microstructure. Thus the mechanical properties and durability of marine concrete are improved.

Effect of Modified High Concentration Boric Acid Solution on Mechanical and Neutron Shielding Properties of Serpentine Shielded Concrete

GAN Xueyu, CHEN Shuai, GENG Haining, LI Zonggang, MA Haosen, CHEN Wei, HOU Suo, LI Qiu

2024, 43(6):  2047-2055. 

Asbtract ( 55 )   PDF (5760KB) ( 19 )  

References | Related Articles | Metrics

Serpentine shielded concrete is a neutron shielding material that can maintain high crystal water content even under high temperature condition for a long time, but its compactness is low and it lacks boron element that can effectively absorb thermal neutrons. As a source of boron, boric acid is an effective material for producing shielded concrete. However, in cement-based hydration systems, the addition of boric acid can inhibit the cement hydration process, leading to deterioration of material strength and durability. This study induced the formation of high boron content and crystalline water content of boric acid in cement slurry by modifying high concentration boric acid solution. The boron content in the system was increased while the inhibitory effect of boric acid on cement hydration was relieved. The effect of modified high concentration boric acid solution on workability, mechanical properties, high-temperature residual compressive strength, microstructure and shielding performance of serpentinite shielded concrete was studied. The results show that the addition of modified high concentration boric acid solution has no adverse effects on the setting time, mechanical properties at room temperature, and high-temperature residual compressive strength of serpentine shielded concrete. After adding modified high concentration boric acid solution, the high-temperature residual compressive strength at 400 ℃ of serpentinite shielding concrete increases by 43.5%, the half value layer at room temperature decreases by 31.7%, and the half value layer decreases by 21.4% after insulation at 350 ℃ to constant weight, enhancing the shielding ability of neutron rays.

Straight Shear Test and Finite Element Simulation of UHPC-NC Interface with Reinforcement Planting

XIAN Xuelei, LIN Mengkai, CHEN Tianming, WANG Daning

2024, 43(6):  2056-2063. 

Asbtract ( 59 )   PDF (6470KB) ( 40 )  

References | Related Articles | Metrics

At present, ultra-high performance concrete (UHPC) is widely used for reinforcement of composite members and normal concrete (NC) structures. After reinforcement, the interface between UHPC and NC becomes the most vulnerable part due to the combined effect of interface normal tensile stress and interface tangential shear stress. Reinforcement planting treatment is a common method to connect the interface between old concrete and new concrete. In this study, the shear strength of UHPC-NC specimens with and without reinforcement planting and the effect of reinforcement rate on shear performance were comprehensively analyzed by straight shear test and finite element simulation. The results show that the shear strength of specimens without reinforcement planting is only 20% of that of integrally cast specimens, while the shear strength of the reinforcement planting specimens could reach 40% to 80%. In specimens without reinforcement planting, the damage form is brittle damage. In reinforcement planting specimens, the development of interface cracks is controlled, the interface shear strength is improved, the slip of interface slip is increased, and the interface is ductile failure.

Bond Strength and Influencing Factors of Magnesium Phosphate Cement Mortar and Concrete in Severe Cold Environment

HOU Tiejun, LI Xiang, ZHANG Chenchen, JIA Xingwen, HOU Pengkun

2024, 43(6):  2064-2072. 

Asbtract ( 55 )   PDF (12153KB) ( 29 )  

References | Related Articles | Metrics

The rapid repair of concrete pavement under severe cold environment requires the repair materials to have high early strength and high bond strength with concrete. Using magnesium phosphate cement (MPC) with high early strength to prepare rapid repair materials is beneficial for achieving rapid repair of concrete pavement under non curing conditions in the winter. The effects of magnesium phosphorus ratio (M/P), boron magnesium ratio (B/M), and water cement ratio (W/C) on bond strength between MPC mortar and ordinary Portland cement concrete (OPC) in severe cold environment were studied, and the interface bonding mechanism were analyzed. The results show that M/P 4~5, B/M 0.02~0.03, and W/C 0.12~0.14 are more conducive to improve bond strength between MPC mortar and OPC in severe cold environment. The 3 h bond strength between MPC mortar and OPC can exceed 2.5 MPa, meeting the requirements for rapid repair of concrete pavement in severe cold environment.

Strength Prediction and Ultrasonic Testing of Desert Sand Concrete after High Temperature

LI Luoyin, DONG Shuibo, LIU Haifeng, YONG Wenjie, CHE Jialing

2024, 43(6):  2073-2083. 

Asbtract ( 47 )   PDF (6738KB) ( 23 )  

References | Related Articles | Metrics

In order to study the compressive properties of desert sand concrete (DSC) after high temperature, desert sand was used to replace medium sand with replacement rate of 0%, 20%, 40%, 60%, 80% and 100% (by mass) to make DSC. The effects of fire temperature and desert sand replacement rate (DSRR) on the rebound value, ultrasonic velocity and compressive strength of DSC were analyzed. The grey prediction strength model of DSC after high temperature was established. Ultrasonic-rebound comprehensive method for measuring strength curve of DSC and formula of fire temperature were deduced. The results show that with the increase of fire temperature, the ignition loss rate of DSC increases gradually, specimen surface colour gradually changes from deep to shallow, and the compressive strength, rebound value, ultrasonic velocity of DSC increase first and then decrease. With the increase of DSRR, the rebound value and compressive strength of DSC increase first and then decrease. When DSRR is equal to 40%, the compressive strength and rebound value of DSC reach the maximum. The NSGM(1,3) model has excellent prediction performance with an average relative error of 8.6%, which can be used to predict the medium and long-term compressive strength of DSC after high temperature. The prediction accuracy of DSC ultrasonic-rebound comprehensive method for measuring strength curve meets the requirements of specification.

Influences of Coarse Aggregate Replacement Ratios on High-Temperature Performance of Recycled Concrete with Manufactured Sand

WANG Fajing, WANG Xinjie, ZHU Pinghua, LIU Xiaolin

2024, 43(6):  2084-2092. 

Asbtract ( 51 )   PDF (6960KB) ( 28 )  

References | Related Articles | Metrics

To explore the influences of different coarse aggregate replacement ratios on the high-temperature performance of recycled concrete with manufactured sand (RCM), RCM specimens were prepared with varying coarse aggregate replacement ratios (0%, 20%, 40%, 60%, 80%, 100%, mass fraction). The surface morphology, mass loss rate, compressive strength, load-deformation curve, and microscopic morphology of RCM were investigated after exposure to high temperatures. Results indicate that the RCM performs well in high-temperature tests below 600 ℃ when the coarse aggregate replacement ratio is between 40% and 60%. At 200 ℃, the specimens in each group show minimal morphological changes, small mass loss rate, and a slight increase in compressive strength. At 400 ℃, cracks begin to appear on the surface of the specimens, with mass loss rate ranging from 4.35% to 6.47%, and compressive strength starts to decline. At this point, the coarse aggregate replacement ratio has a minor impact. At 600 ℃, significant changes in surface morphology are observed, with mass loss rate increasing to 6.42%~8.70%, and compressive strength eventually decreasing to around 80% of the baseline strength. Specimens with coarse aggregate replacement ratio of 40%~60% perform well under these conditions. At 800 ℃, the surface morphology of specimens in all groups intensifies further. The impact becomes particularly pronounced for coarse aggregate replacement ratio exceeding 60%. Simultaneously, various performance parameters indicate that the concrete has experienced a complete loss of effectiveness at this temperature.

Corrosion Effects of Vitamins on Steel Bar in Simulated Pore Solution of Concrete Containing Chlorine

MA Xinmei, WEN Yong, TIAN Peifeng, LIN Haimeng, SHAO Shuai

2024, 43(6):  2093-2101. 

Asbtract ( 50 )   PDF (8752KB) ( 33 )  

References | Related Articles | Metrics

In order to study the corrosion effect of vitamin corrosion inhibitor in reinforced concrete systems,the effects of thiamine (VitB1), nicotinic acid (VitB3), pyridoxine (VitB6) and ascorbic acid (VitC) on steel reinforcement in simulated pore solutions of concrete containing chlorine was investigated using dynamic potential polarization and electrochemical impedance spectroscopy tests. The mechanism of vitamin corrosion inhibition on steel reinforcement was also discussed based on density general function theory with quantum chemical calculations. The results show that VitB6 has the best corrosion inhibition effect in simulated pore solution of concrete containing 0.05 mol/L NaCl because of the strongest bonding stability between its highest occupied molecular orbital and the 3d orbital of iron. All four vitamins have a specific concentration value to achieve the best corrosion inhibition effect IE. At this time, VitB1 and VitB3 are anodic corrosion inhibitors and VitB6 and VitC are mixed corrosion inhibitors. With the increase of vitamin concentration, the IE tends to fluctuate inversely, which is due to the inhibition of cathodic reaction caused by the adsorption of polar groups on steel surface, further aggravating the imbalance between cathode and anode.

Mesoscopic Simulation of Chloride Ion Transport Mechanism in Concrete under Freeze-Thaw Cycles

LIANG Qiuqun, CHEN Xuandong, HU Xiang

2024, 43(6):  2102-2110. 

Asbtract ( 62 )   PDF (7213KB) ( 32 )  

References | Related Articles | Metrics

Based on the classical stress level-fatigue life equation, a mathematical expression for chloride ion diffusion coefficient was proposed with the number of freeze-thaw cycles as independent variable. Furthermore, a three-dimensional mesoscopic numerical model of chloride ion transport in concrete under freeze-thaw cycles was established to investigate the effects of freeze-thaw cycles, mesoscopic structural characteristics of concrete, and bonding effects on chloride ion transport behavior. The results show that the freeze thaw cycle can promote chloride ion diffusion, and this promotion effect is significant when the number of freeze thaw cycles approaches the limit number of freeze thaw cycles. Furthermore, the mechanism of interfacial transition zone promoting chloride ion diffusion is revealed by simulating the diffusion trajectory of chloride ion in concrete meso-structure. Finally, through the simulation of the long-term diffusion performance of chloride ions, it is found that there is a saturated area of bound chloride ion near the ingress surface. And in the saturated area of bound chloride, the concrete loses the curing ability of free chloride and promotes chloride ion diffusion.

Life Prediction of Polypropylene Fiber Reinforced Concrete under Salt-Freeze Erosion Environment

XU Cundong, WANG Zhihang, CHEN Jiahao, LI Zhun, WANG Hairuo, XU Hui

2024, 43(6):  2111-2120. 

Asbtract ( 54 )   PDF (9518KB) ( 43 )  

References | Related Articles | Metrics

In response to the problem of reduced durability of concrete structures in the northwest region of China under salt frost erosion, this study selected concrete specimens with different polypropylene fiber contents (0, 0.6, 0.9, 1.2, 1.5 kg·m^-3) and placed them in clear water, 3%NaCl, and 5%Na₂SO₄ solutions for freeze-thaw cycle testing. The changes in mass loss rate, dynamic elastic modulus and compressive strength of specimens were analyzed, and standard models were established based on Weibull theory and grey theory to predict the maximum service life of polypropylene fiber reinforced concrete structures. At the same time, SEM was used to analyze the mechanism of polypropylene fiber reinforced concrete. The results show that the damage caused by clear water freeze-thaw conditions to concrete is lower than that caused by salt freeze-thaw erosion, with chloride salt causing the most severe erosion damage to mechanical properties of concrete. The infiltration of polypropylene fibers can effectively slow down the degradation rate of mechanical properties of concrete under freeze-thaw erosion and weaken the impact of external erosion on compressive strength. The optimal effect is achieved when the fiber content reaches 1.2 kg·m^-3. The life prediction results of grey prediction model and Weibull model are roughly similar. The grey prediction model can only make large-scale inferences based on data currently contained, while Weibull model has more accurate prediction results. This result can provide theoretical guidance and basis for studying the mechanical properties of concrete and selecting the best model to predict the service life of concrete.

Preparation and Properties of Chloride Resistant Concrete with Manufactured Sand and Extra Fine Sand

WANG Wei, LAI Zengcheng, TAN Peng, JU Zhicheng, YANG Haicheng, FAN Zhihong

2024, 43(6):  2121-2129. 

Asbtract ( 52 )   PDF (4241KB) ( 29 )  

References | Related Articles | Metrics

Using manufactured sand, extra fine sand and other materials to prepare chloride resistance concrete is of great significance to reduce production costs and improve the service life of bridges in coastal areas. In this study, the chloride resistance of concrete was improved by optimizing aggregate design and cement paste composition. The effects of aggregate gradation, extra fine sand content, sand ratio, water-binder ratio and cementitious material type on concrete performance were studied. The results show that the chloride diffusion coefficient decreases from 4.0×10^-12 m²/s to 2.9×10^-12 m²/s when the mass fraction of 8~16 mm gravel increases from 50% to 80%. When 50% (mass fraction) manufactured sand is replaced by extra fine sand, the chloride diffusion coefficient is 3.6×10^-12 m²/s, which can still meet the design requirements. With the increase of sand ratio, the chloride diffusion coefficient decreases first and then increases. The water-binder ratio is controlled in the range of 0.36~0.38, and the chloride diffusion coefficient is less than 3.5×10^-12 m²/s. The hydration of slag component improves the pore structure of concrete, and forms more AFm and C-S-H, which improves the chloride binding capacity. The chloride diffusion coefficient of concrete with slag cement is 40% lower than that of OPC.

Permeability Resistance Test of Steel-PVA Hybrid Fiber High Performance Concrete

XU Chengxiang, ZHANG Jiaqi

2024, 43(6):  2130-2136. 

Asbtract ( 58 )   PDF (10539KB) ( 28 )  

References | Related Articles | Metrics

In order to investigate the effects of steel fiber, polyvinyl alcohol (PVA) fiber and mineral powder contnet on permeability resistance of steel-PVA hybrid fiber high performance concrete (HFHPC). The orthogonal experiment was designed to conduct the permeability resistance test of steel-PVA HFHPC, and the test results were analyzed through range analysis, variance analysis and regression analysis. The results show that the influence degree on the impermeability of HFHPC is steel fiber, mineral powder and PVA fiber from high to low. In the range of test level, the optimal horizontal combination of impermeability of concrete specimens is as follows: steel fiber volume fraction of 1.0%, PVA fiber volume fraction of 0.7% and slag powder mass replacement rate 20%. When the steel fiber volume fraction exceeds 1.0%, the impermeability of HFHPC decreases slightly, but it is still higher than that of standard plain concrete. Finally, multiple regression analysis is used to establish the prediction model of HFHPC permeability and steel fiber, PVA fiber and mineral powder.

Cracking Behavior and Fracture Toughness of Concrete Strengthened by Single/Mixed Amorphous Alloy Fiber and Steel Fiber

QIAO Xiantao, YU Peng, CHEN Xijian, ZHOU Jiale, ZHANG Lianjie, LI Jianpeng

2024, 43(6):  2137-2148. 

Asbtract ( 60 )   PDF (10565KB) ( 42 )  

References | Related Articles | Metrics

To reveal cracking resistance of fiber reinforced concrete (FRC), an experimental investigation was conducted on concrete with various types of fibers (straight steel fiber, amorphous alloy straight fiber, and steel fiber+amorphous alloy fiber) and various volume fractions (1.0%, 1.5% and 2.0%) to evaluate early cracking behavior and post-hardened fracture toughness. First, the concrete early cracking feature was quantitatively analyzed by using plate method and image quantitative technique, aiming to evaluate early cracking behavior of FRC. Then, the three-point bending tests were conducted on notched prism specimens, the hardened fracture toughness of FRC was analyzed and assessed based on the double K fracture parameters. The results show that the single steel fiber reinforced concrete and hybrid fiber concrete exhibit the best cracking resistance at early age. As the fiber fraction increases from 1.0% to 2.0%, the unstable fracture toughness of steel fiber, amorphous alloy fiber, and hybrid fiber reinforced concrete increases by 58.9%, 44.3% and 55.5%, respectively. Meanwhile, the fracture energy of hybrid fiber concrete with 2.0% fiber reaches 11.8 times that of normal concrete. It shows that steel and amorphous alloy fibers have a synergistic effect at different periods of concrete hardening process. As a result, steel fiber and amorphous alloy fiber have a synergistic effect at the different periods of the hardening process, the hybrid steel and amorphous alloy fibers can not only prevent the early-age concrete plastic cracking but also effectively control the formulation and propagation of post-hardened tensile cracks, thus, achieving a staged anti-crack purpose. Considering the early cracking properties, post-hardening tensile properties, and fracture properties of concrete, the overall performance of hybrid fiber concrete with the same fiber content shows better performance.

Solid Waste and Eco-Materials

Influence of Undisturbed Sea Sand on Mechanical Properties of Concrete

ZHENG Jianlan, WANG Yasi, YE Yan

2024, 43(6):  2149-2156. 

Asbtract ( 47 )   PDF (4889KB) ( 23 )  

References | Related Articles | Metrics

In order to explore the mechanical properties of undisturbed sea sand concrete with high chlorine concentration and high shell content, taking the chloride ion content and shell content of sea sand as variables, nine groups of sea sand concrete were designed and prepared to carry out concrete cube compressive strength test and uniaxial compressive stress-strain curve test, and compared with ordinary concrete. The results show that with the increase of chloride ion content, the pore structure of concrete becomes finer, the early strength increases, the peak stress of uniaxial compressive stress-strain complete curve increases, the peak strain decreases, and the elastic modulus increases. With the increase of shell content, the slump of concrete decreases significantly, the pore structure of concrete becomes looser, the strength decreases, and the peak stress of uniaxial compressive stress-strain complete curve decreases, the peak strain increases, and the elastic modulus decreases. Finally, based on the existing models, the formula for calculating the model parameters of chloride ion content and shell content is put forward.

Preparation and High-Strength Micro-Expansion Mechanism of CFB Fly Ash Compaction Slurry

ZHOU Mingkai, RAO Ke, MENG Xiuyuan, WANG Yuqiang

2024, 43(6):  2157-2167. 

Asbtract ( 39 )   PDF (14037KB) ( 12 )  

References | Related Articles | Metrics

The activity and expansibility of circulating fluidized bed coal-fired sulfur-fixed ash (CFB fly ash) were utilized to prepare compaction slurry. The effects of CFB fly ash content and water-binder ratio on the workability, strength and expansion rate of the compaction slurry were investigated.CFB fly ash and mineral powder were mixed in different ratios, and the high-strength and micro-expansion characteristics of CFB fly ash compaction slurry were studied and verified by XRD and SEM analyses. The results show that, with the increase of CFB fly ash replacing cement content, the water demand of the compaction slurry increases and the compressive strength decreases. The 28 d compressive strength of the specimen with 20% (mass fraction) CFB fly ash is close to that of the base sample, up to 85.8 MPa, while the flexural strength rises first and then decreases, and the expansion rate rises sequentially. With the increase of water consumption, the expansion rate decreases but is positive. With the increase of the rate of CFB fly ash replacing mineral powder, the workability decreases, and the 28 d compressive strength rises first and then decreases. The specimen with 20% (mass fraction) CFB fly ash and 10% (mass fraction) mineral powder has the highest 28 d compressive strength, which is 99.8 MPa, and the expansion rate has been increasing. The various properties of compression slurry with CFB fly ash and mineral powder meet the requirements of the iron standard. CFB fly ash not only expands by its own hydration, but also can activate the activity of mineral powder, resulting in a composite enhancement effect.

Fluidity and Mechanical Properties of Waste Glass Powder-Metakaolin Geopolymer Mortar

PENG Lijuan, KE Guojun, SONG Baixing, JIANG Tian, WANG Wenqing

2024, 43(6):  2168-2175. 

Asbtract ( 60 )   PDF (5250KB) ( 34 )  

References | Related Articles | Metrics

Waste glass powder and metakaolin were used to prepare geopolymer mortar. The effects of alkali activator with different sodium silicate modulus and liquid-solid ratios on the fluidity and mechanical properties of the waste glass powder-metakaolin geopolymer mortar were investigated, and the crystal structure, thermochemistry, pore structure, and micromorphology of the geopolymer mortar were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential scanning thermal (TG-DSC), mercury in piezoelectricity (MIP), and scanning electron microscopy (SEM). The results show that the sodium silicate modulus and liquid-solid ratio have more obvious effects on the fluidity and mechanical properties of the geopolymer mortar. With the increase of sodium silicate modulus, the fluidity and strength of geopolymer mortar increase first and then decrease. When the sodium silicate modulus is 1.25, the alkali activator has the best excitation effect on the material, which increases the degree of reaction of the geopolymer, generates more hydration products, optimizes the pore structure of the matrix, and the compressive strength of 28 d reaches 43.0 MPa. The increase of liquid-solid ratio improves the fluidity of the geopolymer mortar, but decreases the compressive strength and has a negative effect on the pore structure. Moreover, the XRD, FTIR and TG-DSC results show that the waste glass in the geopolymer participates in the hydration reaction, provides Ca²⁺, and promotes the generation of C-S-H and C-A-S-H gels.

Performance of Slag-Based Geopolymer Flow Shield-Cured Soil

NIU Jiadong, DU Yunxing, ZHANG Zicheng, LI Yanqiu, QIN Baokun

2024, 43(6):  2176-2185. 

Asbtract ( 59 )   PDF (8798KB) ( 33 )  

References | Related Articles | Metrics

In order to achieve the resource utilization of high moisture content shield soil in underground engineering and explore the feasibility of using geopolymer materials to solidify shield soil, this paper adopts slag-base geopolymer to solidify shield soil. By studying the influences of alkali activator modulus, mineral ratio, alkali activator dosage and temperature on unconfined compressive strength and engineering performance of different types of shield-cured soil, the design of cured soil mix proportion was determined. The influence of geopolymer content on water stability of cured soil was studied. Microscopic analysis of shield-cured soil using SEM to reveal the solidification mechanism. The results show that under the proposed water solid ratio in the test, the two kinds of fluid shield-cured soil with different soil properties have good mechanical and engineering properties. The aggregate of slag base produces amorphous gel, which enhances the cementation and compactness between soil particles. The unconfined compressive strength of shield-cured soil with 22% dry soil mass as cementing agent can reach 5.38 MPa in 28 d under standard curing, 8.08 MPa under 40 ℃ curing, and the water stability coefficient can reach 0.98.

Preparation of High Strength Gypsum Product with Wet-Base α-Hemihydrous Gypsum

ZHOU Mingkai, WANG Xiao, GAO Peng, WANG Yuqiang

2024, 43(6):  2186-2197. 

Asbtract ( 41 )   PDF (17600KB) ( 20 )  

References | Related Articles | Metrics

In order to produce high strength gypsum products from wet-base α-hemihydrous gypsum, the ideal preparation method was identified by analyzing the effects of aging time, grinding time, molding temperature and retarder content on setting time and strength of high strength gypsum. Additionally, scanning electron microscopy and X-ray diffraction were used to clarify how each aspect affected strength. The results show that longer aging period results in lower strength and shorter setting duration of gypsum. As the grinding time prolongs, the setting time of gypsum significantly shortens, and the strength of product increases first and then decreases. The higher the slurry temperature is, the longer the gypsum setting time is, and the lower the product strength is. The optimal preparation process is aging time of 5 min, grinding time of 20 s, and slurry temperature of 20 ℃. On this basis, adding 0.08% (mass fraction) retarder can effectively prolong the setting time of gypsum and improve the hardening strength. The prepared gypsum products have excellent performance, with a drying flexural strength of 14.1 MPa and a drying compressive strength of 58.3 MPa. The microscopic test results indicate that various process parameters can affect the compactness of the internal structure of gypsum and the growth and development of dihydrate gypsum crystals by changing the water content and hydration process of gypsum, ultimately affecting the hardening strength of product.

Adsorption Characteristics of Recycled Sand Derived from Waste Concrete

CHENG Huan, LI Huajian, HUANG Fali, WANG Zhen, YI Zhonglai

2024, 43(6):  2198-2205. 

Asbtract ( 63 )   PDF (5301KB) ( 30 )  

References | Related Articles | Metrics

In order to solve the problem of rapid loss of concrete workability caused by high adsorption of recycled sand, six kinds of recycled sands of C20~C60 were used as objects. The pore structure characteristics of recycled sand were tested by mercury intrusion and low-temperature liquid nitrogen adsorption methods, and the physical composition of recycled sand was tested by X-ray diffraction (XRD). The adsorption law of recycled sand on water, methylene blue, and superplasticizer was explored. The results show that the water absorption rate of recycled sand decreases with the increase of strength grade of waste concrete materials, which is closely related to pore structure. The adsorption of recycled sand on methylene blue decreases with the decrease of clay mineral content, and there is no significant correlation with pore structure. The adsorption of recycled sand on superplasticizer is affected by both pore structure and clay mineral, but mainly depends on clay mineral content.

Effect of Composite Fluxing Agent on Melting Temperature and Phase of Fly Ash from Waste Incineration

LU Fanjie, LI Changcheng, YE Jiayuan, LIU Qiming

2024, 43(6):  2206-2216. 

Asbtract ( 43 )   PDF (24034KB) ( 18 )  

References | Related Articles | Metrics

High temperature melting vitrification is the safest and harmless disposal technology for fly ash from hazardous waste incineration. Fly ash with high calcium content was used as the research object to melt fly ash with low temperature by introducing SiO₂, H₃BO₃ and CaF₂ fluxing agents. The melting temperature, phase change and heavy metal leaching of fly ash were characterized by X-ray diffractometer, ash melting point analyzer and inductively coupled plasma atomic emission spectrometer. The results show that when the alkalinity of fly ash is adjusted to 1.10 by SiO₂ (27.9%, mass fraction), CaSiO₃ minerals with low melting point are formed, and the melting point of fly ash decreases from above 1 400 ℃ to 1 300 ℃. H₃BO₃ (4.5%, mass fraction) and CaF₂ (7.0%, mass fraction) are introduced as fluxing agents, and the melting temperature is further reduced to 1 200 ℃, but SiO₂ is overdoped. After optimization, the composite fluxing agent formula is SiO₂ (20.0%, mass fraction), H₃BO₃ (4.5%, mass fraction) and CaF₂ (7.0%, mass fraction), and the minimum melting temperature of fly ash is 1 124 ℃, the vitreous content of the melt product reaches 87% (mass fraction), and the harmful substances of acid leaching are lower than the limit value, meeting the technical requirements of GB/T 41015—2021 standard for vitrification products.

Strength and Consolidation Mechanism of Glacial Moraine Solidified with Water Glass

YANG Chaoyi, HAN Jiangfeng, ZHU Qiankun, DING Linna, BIAN Libo, LIU Juanhong

2024, 43(6):  2217-2224. 

Asbtract ( 39 )   PDF (7919KB) ( 22 )  

References | Related Articles | Metrics

In order to solve the problem of ground collapse and mudslide caused by the accumulation of loose moraine on the surface of Pulang copper mine in the process of mining, this article prepared a solidified material to solidify moraine with water glass composite ester curing agent. The compressive strength of moraine solidified body was studied, and the consolidation mechanism of water glass composite ester curing agent for consolidating moraine was explored through XRD, FTIR, DSC-TG and SEM. The results show that the moraine solidified body 28 d compressive strength can reach up to 2.05 MPa, indicating good consolidation performance. Under the action of ester curing agent, the hydrolysate of water glass reacts with the hydrolysate of ester curing agent to produce sodium acetate and silicon gel, and silicon gel plays a role in filling the gap between moraine particles and cementing moraine particles.

Ceramics

Research Progress of Pressureless Sintered Silicon Carbide Bulletproof Ceramic Materials

DONG Xinbao, REN Yi, WANG Yang, LIU Futian

2024, 43(6):  2225-2240. 

Asbtract ( 142 )   PDF (7923KB) ( 100 )  

References | Related Articles | Metrics

As the international situation continues to change and conflicts in various countries intensify, improving national defense forces is a necessary condition to ensure the stable development of the country, and bulletproof armor is a key part of it. Pressureless sintered silicon carbide ceramics have been widely used in the field of bulletproof armor because of its simple preparation process and excellent mechanical properties of low density, high hardness and high strength. The hardness and fracture toughness of pressureless sintered silicon carbide bulletproof ceramics directly determine the quality of bulletproof performance. Promoting sintering densification and multi-phase composite sintering are the key ways to improve the hardness and fracture toughness of pressureless sintered silicon carbide ceramics. This study summarizes the research progress of pressureless sintered silicon carbide bulletproof ceramic materials in recent years, focusing on the sintering aids, toughening methods, composite form of pressureless sintered silicon carbide bulletproof ceramic materials.

Preparation and Properties of Aluminum Titanate-Cordierite Composite Ceramics

HUANG Xuehui, CHEN Wenzhen, DENG Penghui, HU Xiang’ao

2024, 43(6):  2241-2249. 

Asbtract ( 71 )   PDF (15725KB) ( 29 )  

References | Related Articles | Metrics

In this study, aluminum titanate-cordierite composite ceramics were successfully prepared by solid-state reaction method, with MgO as a stabilizer and cordierite as a reinforcement. The effects of MgO, cordierite, and sintering temperature on the phase composition, microstructure, sintering performance, and thermodynamic properties of the composite ceramics were systematically investigated. The experimental results show that the introduction of MgO promotes the synthesis and growth of aluminum titanate grains, reduces the sintering temperature, and improves the thermal stability of aluminum titanate ceramics by forming a solid solution of Mg_xAl_2(1-x)Ti_(1+x)O₅. Cordierite plays an important role in sintering densification and mechanical properties. Under the sintering condition of 1 325 ℃, the sample (MgO content of 8.00%, cordierite content of 15.00%) exhibits excellent performance, with a bulk density of 3.49 g/cm³, a porosity of only 2.2%, a flexural strength of 66.8 MPa, and a thermal expansion coefficient of 2.6×10^-6 K^-1 (room temperature to 1 000 ℃). The research results provide new insights for the design and preparation of high-temperature structural ceramics with excellent comprehensive performance.

Effects of Al₂O₃ Particle Sizes on Microstructure and Properties of CA₆ Lightweight Ceramic Materials

SHEN Tianzi, LI Wenfeng, GUO Huishi, CAO Jinjin, HOU Yonggai, DU Juan

2024, 43(6):  2250-2255. 

Asbtract ( 70 )   PDF (4308KB) ( 40 )  

References | Related Articles | Metrics

In order to study the effects of Al₂O₃ particle sizes on microstructure and properties of CA₆ lightweight ceramic materials, lightweight calcium carbonate with an average particle size of 15 μm and α-Al₂O₃ with average particle sizes of 80, 61, 45 and 38 μm were used as calcium oxide and alumina sources, respectively. CA₆ lightweight ceramic materials were prepared by foaming method combined with in-situ sintering technology after being heated at 1 550 ℃ for 5 h. Effects of Al₂O₃ starting materials with different particle sizes on their physical properties, phase composition and microstructure were investigated. The results show that with the decrease of α-Al₂O₃ particle size, the linear shrinkage, bulk density and thermal conductivity of CA₆ lightweight ceramic materials gradually decreases, while their apparent porosity gradually increases and their compressive strength increases firstly and then decreases. Comprehensively considered, the specimen prepared by α-Al₂O₃ with an average particle size of 45 μm as alumina source has better comprehensive performance, and its apparent porosity, thermal conductivity and compressive strength are 87.8%, 0.149 W·m^-1·K^-1 and 0.29 MPa, respectively, which can better meet the needs of application.

Effect of SiC Content on Properties of Aluminum Matrix Composite Materials

WANG Haitao, LIN Chen, FAN Zimin, TANG Mingqiang, ZHAO Fang, LE Chen, CHEN Yihua, HUANG Yuancheng

2024, 43(6):  2256-2261. 

Asbtract ( 64 )   PDF (7099KB) ( 56 )  

References | Related Articles | Metrics

SiC reinforced aluminum matrix composites are widely used in aerospace, electronic packaging and transportation due to their high specific strength, high thermal conductivity and high wear resistance. In this paper, SiC particle reinforced aluminum matrix composites were prepared by hot pressing sintering. The effects of SiC content on the microstructure and mechanical properties of aluminum matrix composites were studied. The phase composition, apparent density and mechanical properties of the samples were determined by X-ray diffraction, Archimedes drainage method, Rockwell hardness analysis and three-point bending method. The microstructure of the samples was analyzed by SEM. The thermal conductivity was measured by laser flash method. The results show that the hardness of the samples increases first and then decreases with the increase of the volume fraction of SiC particles from 0% to 60%, and reaches the maximum value of 90 HRB when the volume fraction of SiC is 50%. The thermal conductivity of the samples increases first and then decreases, and reaches the maximum value of 324.05 W/(m·K) when the volume fraction of SiC is 30%. With the increase of SiC volume fraction, the metal matrix and the reinforcement are closely combined without obvious pores. When the volume fraction of SiC increases to 60%, the porosity of the samples increases, the consistency decreases, and the strength decreases.

Oriented Growth Control and Photocatalytic Activity of FeWO₄ Crystalline Glazes

LI Jiayin, WU Jintao, HUANG Lingyan, ZHANG Jinjin, ZHONG Xinzi, CHENG Kemu, LIANG Duo, WU Yang, WANG Qinggang, LIU Yijun, XIAO Libiao, CAO Liyun, CHENG Zhiwen, HUANG Jianfeng

2024, 43(6):  2262-2268. 

Asbtract ( 63 )   PDF (11468KB) ( 29 )  

References | Related Articles | Metrics

The crystalline glaze structure with photocatalytic activity has important application value for the surface functionalization of ceramic panels, but the structure control of functionalized surface crystalline glaze and the influence of its growth mode on photocatalytic activity are still unclear. This study used tungsten trioxide, ferrous sulfate, aluminum phosphate, kaolin, and other raw materials to successfully produce crystalline glazes with exposed high nucleophilic crystal faces by regulating FeWO₄ with different growth orientation structures at 1 080 ℃. The results indicate that crystalline glaze layers with different orientations exhibit different crystal surface exposures. Crystalline glazes grown with different orientations can provide higher catalytic activity and promote the exposure of highly nucleophilic (100) crystal surfaces, thereby improving the photocatalytic performance of ceramic plate surface. This study can provide theoretical and practical references for the design and regulation of surface functionalization of photo functionalized crystalline glaze materials.

Influence of Iron Oxide on Coloration and Crystallization Behavior of Jian Kiln Oil-Spot Glaze

JIANG Caishui, ZHOU Jianer, FANG Yuan, LIU Kun, BAO Qifu, WU Junming

2024, 43(6):  2269-2278. 

Asbtract ( 79 )   PDF (21319KB) ( 72 )  

References | Related Articles | Metrics

Jian kiln oil-spot glaze is one of the most typical iron crystal precipitation glazes in ancient China, and it is important to clarify the influence of iron oxide on precipitation glazes coloration and crystal precipitation, to provide a scientific basis and theoretical guidance for the development and innovation of iron crystal precipitation glazes with a variety of coloration effects. In this paper, XRD, Raman, SEM and EDS testing methods were used to investigate the microstructure of the precipitated crystals in glaze melt and the change rules of glaze coloration with different iron oxide content, and to reveal the mechanism of the glaze crystal structure on coloration. The results show that with the increase of iron oxide content, the glaze surface precipitates brownish-yellow, silver-blue, silver-white, silver-white and reddish-brown crystal spots, and the crystal spots are colored by chemical color and structural color coupling effect of crystals. The iron enrichment in the middle area of crystal spot is higher than that in edge area, and the phase change from ε-Fe₂O₃ to α-Fe₂O₃ takes place preferentially, forming different color effects. The middle area first precipitates 2~4 μm leaf-shaped ε-Fe₂O₃ crystals, with brownish yellow. With the increase of iron oxide content, the glaze layer precipitates with the glaze surface parallel to the directional arrangement of rod-shaped α-Fe₂O₃ crystals to form crystalline thin film, which produces a strong reflection of light, being silver-white. When the iron oxide continues to increase, the glaze precipitation of 10~20 μm dendritic α-Fe₂O₃ crystals penetrates the crystalline thin film, the structural color (silver) produced by the film is weakened, and the chemical color of α-Fe₂O₃ (reddish brown) is enhanced. The coupling is silver-white with reddish brown. The edge area first precipitates a large number of 30~50 nm grains, resulting in Rayleigh scattering as blue. With the increase of iron oxide content, the surface layer of rod-like crystals also forms a crystal film and the lower layer of film precipitates 100~200 nm plate nanocrystals to form amorphous photonic crystals. The coherent scattering is blue, and the reflected silver-white is coupled with silver blue.

Microstructure and Color Analysis of Jun Porcelain Glaze Layer Regulated by Nano Iron Oxide

LI Xu, ZHU Congxu, FA Wenjun, ZHANG Yange, FENG Minghua, GUO Zhiyong, KONG Chunsheng, ZHENG Zhi

2024, 43(6):  2279-2286. 

Asbtract ( 69 )   PDF (11017KB) ( 26 )  

References | Related Articles | Metrics

Different mass fractions of nano iron oxide were added to Jun porcelain glaze, and analyzed changes in the color and microstructure of Jun porcelain after firing in reducing atmosphere (96%Ar/4%H₂) and oxidizing atmosphere (air). The color change was studied by spectrophotometer, the phase composition of Jun porcelain was studied by X-ray diffractometer and Raman spectrometer, and microstructure of glaze layer was studied by SEM. The results show that with an increase in the gradient of nano iron oxide content, Jun porcelain specimens changes from light blue to blue, then to cyan gray under reducing atmosphere, and from white to yellow, and then to sauce black under oxidizing atmosphere. When nano iron oxide content in the glaze layer reaches 3.0% (mass fraction), the SiO₂ crystal phase on the glaze completely disappeares and the glaze appeares amorphous. With the increase of nano iron oxide content, the glaze exhibites a liquid-liquid phase separation structure, and the microstructure size of reducing atmosphere increases from 85 nm to 150 nm, with a relative increase in Fe²⁺ content. After the glaze of Jun porcelain reaches glass transition in an oxidizing atmosphere, the size of the phase separation structure increased from 217 nm to 307 nm.

Glass

Structure and Leaching Resistance of Ba(NO₃)₂-Pretreated High-Level Liquid Glass Waste Form

NING Haixia, AN Hongna, LEI Jie, WANG Bin, WU Lang

2024, 43(6):  2287-2293. 

Asbtract ( 58 )   PDF (9654KB) ( 25 )  

References | Related Articles | Metrics

In order to increase solubility of sulfur in borosilicate glass, SO^2-₄ ions in simulated high-level liquid waste (HLLW) with relatively high content of sulfur and sodium were pretreated by adding Ba(NO₃)₂ solution, and then borosilicate glass waste form was prepared by melt-quenching method. The effects of pretreated HLLW on the structure and leaching resistance were mainly investigated. The results show that the waste loading can be increased to 23% (mass fraction) without phase separation after the Ba(NO₃)₂ pretreatment. The normalized elemental mass loss of Na, B and Si of the HLLW-loaded samples are one order of magnitude lower than that of the pure borosilicate glass. Furthermore, the leaching resistance of the glass waste form has no significant change with increasing HLLW content. ¹¹B and ²⁹Si MAS NMR analyses indicate that part of BO₃ transforms into BO₄ structural units and a polymerization of the glass network occurs after HLLW addition.

Numerical Simulation of Stone Wool Melt in Direct Current Furnace

HE Dewei, SUN Shibing, KANG Junqi, ZHANG Xudong, CHEN Zilong, WANG Jingjing, TIAN Yingliang

2024, 43(6):  2294-2300. 

Asbtract ( 81 )   PDF (8595KB) ( 33 )  

References | Related Articles | Metrics

ANSYS software was used for numerical simulation of stone wool melt in electric melting furnace. Under stable voltage 130 V, stable melt height 1 600 mm and stable inlet and outlet state, the insertion depth of cathode electrode was changed to study the temperature distribution, flow field distribution and current density distribution of the melting in electric melting furnace. The results show that the melt forms a high temperature zone between the cathode and anode and around the electrode, The temperature decreases from anode to cathode and from top to bottom on the symmetrical side of the inlet, while the temperature increases from top to bottom on the inlet side. With the increase of cathode insertion depth, the overall temperature and corresponding current density of the melt increase. The deeper the cathode insertion depth is, the greater the temperature rise of the whole temperature field is. At the inlet side and the outlet side, the melt forms a circulation due to natural convection, and the self-stirring and self-homogenization of the circulation have important technological significance for melt homogenization. Changing the cathode insertion depth can improve the melt control ability and improve the subsequent fiber forming effect and quality.

New Functional Materials

Preparation and Energy Storage Properties of CaBi₄Ti₄O₁₅-Bi(Fe_0.93Mn_0.05Ti_0.02)O₃ Ferroelectric Solid Solution Thin Films

YU Zhiyao, WANG Wenwen, SI Jingxiang, YUAN Xiufang, LI Chenglong, LIN Xiujuan, YANG Changhong

2024, 43(6):  2301-2309. 

Asbtract ( 57 )   PDF (12010KB) ( 27 )  

References | Related Articles | Metrics

(1-x)CaBi₄Ti₄O₁₅-xBi(Fe_0.93Mn_0.05Ti_0.02)O₃(CBT-xBFMT, x=0, 0.05, 0.10, 0.15) solid solution films were successfully prepared on Pt(111)/TiO₂/SiO₂/Si substrates using metal organic decomposition combined with spin coating technology. And the energy storage properties of CBT thin films were systematically studied by X-ray diffractometer, field emission scanning electron microscope, ferroelectric analyzer and impedance analyzer. The results show that the prepared films all exhibit a polycrystalline bismuth layered structure without other phase formation. The addition of BFMT into thin film obviously enhances the maximum polarization strength P_m and breakdown field strength E_b, reduces the leakage current density. With the increase of BFMT solid solution, the breakdown field strength E_b of CBT-xBFMT film increases first and then decreases, and reaches the maximum value at x=0.10. The maximum polarization strength P_m gradually increases, and the largest polarization strength difference is obtained at x=0.10. The largest polarization intensity difference and breakdown field strength make CBT-0.10BFMT film has the best energy storage properties. The recoverable energy storage density W_rec and energy storage efficiency η of CBT-0.10BFMT film are up to 82.8 J/cm³ and 78.3%, respectively. And its energy storage characteristic has good temperature stability in the temperature range of 25~150 ℃. Therefore, CBT-0.10BFMT ferroelectric film is expected to be used in environmentally friendly micro energy storage devices.

Road Materials

Effect of Surface Treatment on Road Performance of Recycled Aggregate-Asphalt Mixture

YANG Biao, YANG Gang, CHEN Jingqun, ZHOU Zuheng, LI Gengying

2024, 43(6):  2310-2316. 

Asbtract ( 45 )   PDF (7528KB) ( 18 )  

References | Related Articles | Metrics

In order to enhance the utilization rate of recycled concrete aggregate (RCA), this paper proposes a method of ionic precipitation (MIP) to treat RCA by using a saturated solution of sodium bisulphate and calcium hydroxide combined with ultrasonic waves and organosilicon hydrophobes. The effects of MIP on the micro-morphology and physical properties of RCA, as well as the oil/stone ratio and road performance of asphalt mixtures, were analyzed. The test results show that the MIP resulted in the surface of RCA covered by a layer of alkaline cementitious materials. Moreover, the pores of RCA are filled with gypsum, calcium hydroxide and ettringite. Consequently, the crushing index, wear value and water absorption rate of RCA are reduced greatly. MIP treatment significantly reduces the optimal asphalt content of RCA-asphalt mixture and enhances interface adhesion, water stability and high-temperature stability. In addition, according to the test results, the replacement of 60% (mass fraction) original coarse aggregates by using of MIP-RCA can construct an asphalt mixture with excellent road performance and a low optimal asphalt content.