Table of Content

15 August 2021, Volume 40 Issue 8

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Cement and Concrete

Research Progress of Tm³⁺-Doped Glass Fibers

QIAN Guoquan, TANG Guowu, WU Minbo, QIAN Qi, CHEN Dongdan, YANG Zhongmin

2021, 40(8):  2471-2484. 

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Fiber lasers operating at 2 μm band are widely used in some fields such as lidar, biomedical, environmental monitoring, and spectroscopy. Tm³⁺-doped glass fiber is an important gain medium for 2 μm band fiber lasers. Starting from the luminescence characteristics of Tm³⁺-doped glasses, the preparation technologies of Tm³⁺-doped glass fiber were introduced. Then, the research progress of Tm³⁺-doped fibers was introduced based on different glass matrix materials. Finally, the key issues that need to be solved in the preparation of high-performance Tm³⁺-doped glass fibers were proposed. The possible solutions and future development trends of Tm³⁺-doped glass fibers were prospected.

Research Progress on Dynamic Mechanical Properties and Anti-Explosion and Impact Resistance Performance of Engineered Cementitious Composite

YANG Jinhong, LI Xiudi, WANG Qifan, LUO Yinjian

2021, 40(8):  2485-2496. 

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Common cement-based materials have weak tensile strength and easy to crack, however, these shortcomings have been overcome by a new type of fiber reinforced cement-based material—engineered cementitious composite (ECC). High ductility, high toughness and high energy dissipation capacity are the distinctive characteristics of ECC, which are attributed to the steady-state cracking process based on the micromechanical design. After the brief introduction of the development background and design mechanism of ECC, this paper reviewed the researches on dynamic mechanical properties and explosion/impact resistance of ECC. Meanwhile, the influences of high strain rate and high temperature on the performance of ECC were analyzed, and the problems that need to be solved in the application of ECC in protection engineering were also pointed out. Finally, suggestions for future researches and developments of ECC were put forward.

Research Progress of Water Dispersed Polymer Emulsion Modified Cement Mortar

SHI Xin, XU Lingling, FENG Tao, HAN Jian, ZHANG Pan

2021, 40(8):  2497-2507. 

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With the rapid development of construction industry and the improvement of engineering quality awareness, the polymer modified cement mortar is widely used because of its excellent performance. Water dispersed polymer emulsion is a polymer admixture widely used in the modified cement mortar. In this paper, the development history of polymer modified cement mortar was introduced. The properties of polymer modified cement mortar were introduced from mechanical properties and durability. The modification mechanism of polymer emulsion for cement mortar was explored, and the research direction of polymer emulsion was discussed.

Performance and Resistance Mechanism of Calcium Sulfoaluminate Cement Subjected to Acids

QI Qiulin, ZHOU Jian, GE Zhongxi, LI Hui, XU Mingfeng, CHEN Zhifeng, ZHANG Zhenqiu, CUI Suping

2021, 40(8):  2508-2514. 

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The mechanical performance of calcium sulfoaluminate cement (CSA) in hydrochloric and sulfuric acids was studied and the resistance mechanism was investigated. The flexural strength of CSA mortar in water and acids was measured respectively and the resistance index was calculated. X-ray diffraction (XRD), thermogravimetric analysis (TGA), electronic computed tomography (CT) scan, and scanning electron microscopy (SEM) were used to analyze the mineral composition and microstructure. It is found that compared with ordinary Portland cement (OPC), CSA shows better resistance to both hydrochloric and sulfuric acids, with higher residual flexural strength and resistance index values. Compared with the portlandite and calcium silicate hydrate (the main hydration production of OPC), the ettringite (the main hydration production of CSA) is harder to react with acids, which is responsible for the better performance of CSA in acids. The deterioration of CSA in hydrochloric acid is attributed to the dissolution of ettringite due to the hydrogen ions, while both hydrogen ions and sulfate cause the deterioration in sulfuric acid.

Influence of Dispersant on Pressure-Sensitive Properties of Graphene Cement-Based Composites

WANG Yue, WANG Qin, ZHENG Haiyu, ZHAN Dafu

2021, 40(8):  2515-2526. 

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Graphene can significantly improve the smart performance of cement-based composites, and dispersants are a key factor affecting the dispersion of graphene and the performance of composites. In this paper, through ultraviolet (UV) spectrophotometer, ultra-depth-of-field microscope, laser particle size analyzer and Zeta potential test, the polycarboxylate water reducing agent (PCE), polyoxyethylene (20) sorbitan monolaurate (TW-20), sodium dodecyl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS) on the dispersion properties of graphene were studied. The effects of four dispersants on the conductivity and pressure-sensitive properties of graphene cement-based composites were studied through DC two-electrode, DC four-electrode and AC two-electrode tests. The results show that in deionized water and cement pore solution, PCE has good dispersibility for graphene due to the synergistic effect of electrostatic repulsion and steric hindrance. In the cement pore solution, the complexation between TW-20, SDS, SDBS and Ca²⁺ leads to a significant decrease in dispersion efficiency. The conductivity and pressure-sensitive properties of graphene cement-based composites are closely related to the dispersion of graphene in the cement matrix. Graphene cement-based composites doped with PCE have the smallest resistivity and the best pressure-sensitive properties. In addition, the air-entraining effects of SDS and SDBS also affect the pore structure of the cement matrix, resulting in increased resistivity and poor pressure sensitivity.

Effects of EPS Particles on Properties of Ultra-Light Cement-Based Composite Thermal Insulation Materials

WU Zihao, WANG Wuxiang, LIU Guangdong, WANG Aijun, ZHANG Leilei, YANG Jun

2021, 40(8):  2527-2533. 

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EPS particles as the ultra-light aggregate of cement-based composite thermal insulation materials have a significant effect on the mechanical and thermal properties of cement-based composite thermal insulation materials. In this paper, the cement as cementing material, EPS particles, mixes, foams and modifiers, water and other as the main raw materials,ultra-light cement-based composite thermal insulation materials (UCIM) with dry apparent density less than 120 kg/m³ were prepared by physical foaming process. Through the design of different volume of EPS particles, the effect of the EPS particlescontent on the foamed concrete matrix pore structure, the strength and thermal performance of ultra-light cement-based composite thermal insulation materials was analyzed. The results show that the appropriate mix content of EPS particles significantly improves the compressive strength and tensile strength of ultra-light cement-based composite thermal insulation materials, and ensures that ultra-light cement-based composite thermal insulation materials have a good thermal performance. Through the synergistic effect of EPS particles and foamed concrete matrix, the mechanical properties and thermal properties are coordinated, and ultra-light cement-based composite thermal insulation materials with high performance are prepared.

Phase Composition Control and Mechanical Property of New Oil Well Cement

NI Xiucheng, CHENG Xiaowei, LI Junwu, WANG Jing, GAO Xianshu, ZHANG Gaoyin, ZHANG Chunmei, LIU Kaiqiang

2021, 40(8):  2534-2545. 

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In order to solve the problem of damage and failure of cementing ring during shale gas exploitation, the ratio of raw materials through mineral composition was calculated and adjusted. The oil well cement phase composition control research was studied by lithofacies, XRD analysis and scanning electron microscopy tests. And the mechanical properties of cement with different mineral compositions and related hydration products were explored. The results show that the compressive and flexural strength of the developed new oil well cement reach 45.3 MPa and 8.9 MPa for 7 d, 54.2 MPa and 9.6 MPa for 28 d, respectively. The 7 d elastic modulus is reduced to 7.1 GPa, which is 14.4% lower than that of G grade oil well cement, showing more excellent mechanical properties. Through microscopic analysis, it is concluded that the mechanism of the enhancement of the mechanical properties of the new oil well cement is due to the change in the mineral composition, which produces more C-S-H gel in the hydration product. At the same time, the increase in the content of the iron phase also produces more iron (aluminum)-rich gels, forming a tight bridge structure between the hydration products, and the overall structure is more compact. The new type of oil well cement has better compressive strength, flexural strength and toughness than G grade oil well cement, which has important reference value for the safe and efficient exploitation of shale gas.

Effects of Corrosion Inhibitors on Mechanical Properties and Corrosion Behavior of Recycled Mortar Mixed with Seawater

LIAN Songsong, MENG Tao, ZHAO Yuxi, LU Yuqi

2021, 40(8):  2546-2553. 

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In view of the durability of reclaimed aggregate mixed with seawater, effects of corrosion inhibitors on mechanical properties and corrosion behavior of recycled mortar mixed with seawater were analyzed and the mechanism was revealed through microscopic experiments such as X-ray diffraction analysis (XRD) and mercury intrusion (MIP). The results show that recycled mortar mixed with seawater has a fast corrosion speed in the early stage, and then the corrosion speed slows down after 7 d and gradually tends to passivation. In addition, aminomethyl propanol has an adverse effect on mechanical properties of the mortar and accelerates the corrosion of steel bars. The main reason is that aminomethyl propanol inhibits the cement hydration process and increases the number of pores. Sodium metasilicate pentahydrate has a significant rust-inhibiting effect, which is beneficial to promote the passivation of steel bars in recycled mortar mixed with seawater. At the same time, sodium metasilicate pentahydrate is helpful to promote the formation of C-S-H in the mortar and optimizes the pore structure, which has little effect on mechanical properties of recycled mortar mixed with seawater. This research provides reference for the improvement of durability and service safety of recycled concrete mixed with seawater.

Composition Design of Pervious Concrete with Water Purification Function

JIA Junhong, YU Yue, GUO Yuguang, NIU Zidong

2021, 40(8):  2554-2563. 

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In order to purify rainwater and supplement groundwater, a class of metakaolin-based geopolymer pervious concrete with water purification function was designed. By studying the effects of chitosan content, alkali activator modulus and concentration of alkali activator on the mechanical and adsorption properties of the metakaolin-based geopolymer, a kind of paste material with high adsorption for pervious concrete was prepared. The effects of volume structure parameters such as bulk porosity of aggregate and P/A (paste aggregate ratio) on water purification, water permeability and mechanical properties of pervious concrete were studied. The results show that with the increase of chitosan content, the strength of metakaolin-based geopolymer increases firstly and then decreases, and the adsorption capacity of Pb²⁺ increases. With the increase of bulk porosity of aggregate, the mechanical and water purification properties of pervious concrete decrease, and the water permeability increases. With the increases of the P/A, the mechanical and water purification properties of pervious concrete increase, while the water permeability decreases. The 28 d compressive strength, permeability coefficient and Pb²⁺ removal rate of pervious concrete with coordinated water purification, permeability and mechanical properties are 20.1 MPa, 0.67 cm/s and 90.5%, respectively.

Effects of MgO and CaO on the Carbonization Resistance of Alkali-Activated Slag Concrete

ZHENG Hao, LIANG Yongning, ZHAN Jianwei, JI Tao

2021, 40(8):  2564-2573. 

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Compared with ordinary Portland cement (OPC) concrete, alkali-activated slag concrete (AASC) has poor carbonization resistance. In this paper, part of slag was replaced by MgO and CaO to prepare AASC to improve its carbonization resistance. The compressive strength and carbonization depth of AASC seeded with MgO and CaO under accelerated carbonization environment at different carbonization ages were studied. The modification mechanism of MgO and CaO on the carbonization resistance of AASC was analyzed by X-ray diffraction (XRD), simultaneous thermal analysis (TG-DTG) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). The results show that MgO and CaO promotes the formation of Mg-Al hydrotalcite and Ca-Al layered structure in AASC, respectively. These two hydration products absorb and consume CO₂ during the carbonization process, then alleviate the decomposition of C-S-H caused by carbonization. In addition, after accelerated carbonization, calcium magnesium carbonate and magnesium carbonate are formed in the AASC blended with MgO, and the amount of calcium carbonate in the AASC blended with CaO increase significantly. These carbonized products effectively fill the pores and hinder the further diffusion of CO₂ into the interior of AASC. Therefore, under the carbonization environment, the AASC blended with MgO and CaO has a higher compressive strength retention rate, a lower carbonization depth, and a better carbonization resistance than pure AASC.

Fatigue Performance Analysis of Steel Fiber Reinforced Concrete Beams Combined with Homogenization Theory

HE Zhengbo, WANG Huiming

2021, 40(8):  2574-2583. 

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Steel fiber reinforced concrete (SFRC) is widely used in engineering. To explore the internal mechanism of fatigue failure phenomenon of SFRC, Mori-Tanaka homogenization theory was used to predict the elastic modulus of SFRC with different steel fiber volume content. Based on the calculated results, a four-point bending finite element model of SFRC beam was established. Miner fatigue damage criterion was used to carry out bending static test and fatigue test of numerical simulation of the experiment. The simulation results are in good agreement with the relevant test results, which verifies the reliability of the model. The fatigue life and fatigue strength of SFRC beams were predicted by using fatigue analysis software. The influences of fiber content, size effect and fiber length on the fatigue life were analyzed. The results show that steel fiber greatly improves the fatigue life of concrete beams, and the lower the stress level and the greater the fiber content are, the higher the improvement range is. The size effect has a certain influence on the fatigue strength and fatigue life, but the influence on the fatigue performance decreases with the increase of component size. The longer the fiber length is, the better the fatigue performance of the SFRC beam is.

Experimental Study on Static Compressive Properties of Aluminum Foam-Steel Fiber Concrete

LIANG Li, WANG Liran, LI Mingshu, GAO Xuanlin, LI Ming

2021, 40(8):  2584-2590. 

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In order to study the compressive properties of aluminum foam-steel fiber concrete composite layer under static load, the universal testing machine was used to test the pore size of aluminum foams of 3 mm to 6 mm, 6 mm to 9 mm, 9 mm to 12 mm. The compressive properties test was carried out on the aluminum foam-steel fiber concrete composite layer specimens with steel fiber content (volume fraction) of 0%, 0.5%, 1.0% and 1.5%, and the mixture properties were analyzed. Based on different pore sizes of aluminum foam and according to the test data, the influence of aluminum foam on the compressive resistance of the aluminum foam-steel fiber reinforced concrete composite layer specimens was analyzed, and the rules were summarized. The results show that when the steel fiber content is 1.5%, the compressive strength of the steel fiber concrete cube increases by 22.6%, positive correlation between them. The compressive strength of foam aluminum wire reinforced concrete composite layer is about 5.3% to 8.2% higher than the steel fiber concrete, and the static compressive stress-strain curves of the aluminum foam-steel fiber concrete composite layer have a platform area, and the platform area gradually becomes longer with the increase of the aperture of the aluminum foamed.

Influences of Auxiliary Cementitious Materials on Strength and Technology of Prestressed High-Strength Concrete Pipe Piles

FAN Qi, DU Hongxiu, ZHAO Zhuang

2021, 40(8):  2591-2599. 

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To optimize the production process of concrete pipe piles, silica fume (SF) and metakaolin (MK) were used as auxiliary cementitious materials. The influences of silica fume and metakaolin on the compressive strength of concrete under different steam curing time were studied.X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) were used to analyze the hydration products and microstructure. The Box-Behnken test was designed by Design-Expert8.0 software, taking silica fume content, metakaolin content and steam curing time as independent variables, the compressive strength of steam curing concrete as the response value, to construct a multi-factor regression equation model. The results show that when the content of silica fume is 8% (mass fraction), the compressive strength slightly increases by 6.2% to 83.6 MPa; the content of metakaolin of 5%, 8% and 10% (mass fraction) improves compressive strength of steam curing concrete. When the steam curing time for 4 h, 8 h and 12 h, the increase of compressive strength of concrete with 10% metakaolin is 15.6%, 13.2% and 13.6% accordingly. The steam curing time of 4 h, 8 h and 12 h has little effect on the compressive strength of concrete. XRD and SEM-EDS results show that both silica fume and metakaolin consume Ca(OH)₂, which improves the early hydration degree of cement and the internal pore structure. The model established by the response surface method predicts that when the mass fraction of silica fume is 6.6%, the mass fraction of metakaolin is 10%, and the steam curing time is 8.6 h, the compressive strength of concrete is the highest with 104.8 MPa, and has a high degree of confidence.

Design of Air Content of Frost Resistance Air-Entrained Concrete in Plateau Area

LI Xuefeng, FU Zhi, WANG Hualao

2021, 40(8):  2600-2608. 

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The effect of low atmospheric pressure environment of plateau on air content loss, the change of bubble spacing coefficient and the critical value of frost resistance durability index were studied through testing the air content, bubble spacing coefficient and frost resistance durability index of air-entrained concrete with different water-binder ratios in plateau and plain areas, and collecting correlative results of domestic and foreign researches. The results show that compared with the plain area, the air content loss of air-entrained concrete increases under low-pressure environment in the plateau, and the air content loss is about 1.0%~1.5% during the hardening process. There is a good linear relationship between the air content of hardened concrete and the logarithm of the bubble spacing coefficient, but the bubble structure of air-entrained concrete may be degraded in the environment of low atmospheric pressure on the plateau. There is also a good linear relationship between the bubble spacing coefficient and frost resistance durability index, and it is not affected by atmospheric pressure. An air content design method of air-entrained concrete in plateau area based on the objective of frost resistance durability of concrete is proposed by taking bubble spacing coefficient as the link.

Research on Humidity Field and Self Restraint Stress Field in Concrete

ZHONG Zhuo, HUANG Lepeng, ZHANG Heng

2021, 40(8):  2609-2621. 

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In order to prevent the cracking of concrete caused by internal restraint, the internal humidity field and self restraint stress field of concrete were studied in this paper. The shrinkage, internal temperature and humidity of concrete under different strength and curing conditions were tested by displacement sensors, temperature and humidity sensors. Afterwards, through theoretical derivation, a theoretical calculation model for the internal humidity, relationship betweenstrain and internal humidity of concrete were established. Studies indicate that the humidity in concrete decreases with the increase of cement hydration and drying. The moisture diffusion coefficient of concrete is a function of its internal humidity. As the distance from the drying surface increases, the internal moisture diffusion coefficient of concrete increases. There is a significant correlation between the shrinkage deformation and the internal humidity of concrete. The calculation model proposed in this paper is in good agreement with the experimental results. The existence of the humidity field in concrete leads to the existence of a strain gradient, which in turn causes the self restraint stress in concrete. Under the same environmental conditions, the internal self restraint stress of high-strength concrete is higher than that of ordinary-strength concrete.

Solid Waste and Eco-Materials

Research Progress on Treatment of Nitrogen and Phosphorus Wastewater with Fly Ash-Based Zeolite

CUI Jiaxin, WANG Lianyong, ZHANG Kun, SUN Yanwen, HAN Jianli

2021, 40(8):  2622-2630. 

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In recent years, fly ash is often used as a raw material for synthetic zeolite due to its low price, high output and similar structure to zeolite. In terms of water treatment, the research on the treatment of nitrogen and phosphorus wastewater with fly ash-based zeolite is quite popular among scholars. The physical and chemical properties and utilization status of fly ash are introduced. Ion exchange, adsorption and catalysis are the main characteristics of fly ash-based zeolite, due to its unique internal structure. The mechanism of nitrogen and phosphorus removal by fly ash-based zeolite is introduced. The focus is on the progress of the treatment of low, medium and high concentrations of ammonia nitrogen wastewater, phosphorus wastewater and nitrogen-phosphorus coexisting wastewater with fly ash-based zeolite. Finally, the current problems in this field and future development trends are analyzed.

Utilization of Alkali-Activated Lead-Zinc Smelting Slag for Chromite Ore Processing Residue Solidification

FANG Lu, HUANG Xiao

2021, 40(8):  2631-2639. 

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Lead-zinc smelting slag (LZSS) was used to prepare alkali-activated materials and solidify chromite ore processing residue (COPR) to realize waste co-treatment. Single-factor and orthogonal experiments were carried out which aim to explore the effects of various parameters (alkali content, water glass modulus, liquid-solid ratio, and initial curing temperature) for alkali-activated LZSS strength. Based on the above experiments, COPR was solidified by alkali-activated LZSS. Additionally, compressive strength and leaching toxicity were the indexes to evaluate the performance of the solidified bodies containing COPR. The results show that when the alkali content is 2.5% (mass fraction, the same below), the water glass modulus is 1.5, the liquid-to-solid ratio is 0.19, the initial curing temperature is 35 ℃, the compressive strength of alkali-activated LZSS reaches up to 84.49 MPa. With the increase of COPR content, the compressive strength of solidified bodies gradually decreases, and when 40% COPR is added, the compressive strength decreases to 1.42 MPa. However, the leaching concentrations of Zn and Cr from all the solidified bodies (the content of COPR is 0%~40%) are far below the critical limits (US EPA Method 1311 and China GB 5085.3—2007). Heavy metal ions in LZSS and COPR are immobilized successfully by chemical and physical means, which is manifested by the analyses of environmental scanning electron microscope with energy dispersive spectrometry, Fourier transform infrared spectrometry, and X-ray diffraction. The results show that alkali-activated LZSS can solidify COPR effectively.

Strength Chatacteristics and Micro-Mechanism of Alkali-Activated Steel Slag-Blast Furnace Slag Road Base Composite Material

WU Min, XIE Shenghua, GE Genwang

2021, 40(8):  2640-2646. 

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Focusing on the three issues of steel slag recycling, the strength enhancement of steel slag-blast furnace slag composite material as well as the microscopic action mechanism, the macroscopic strength of the mixture under different curing ages was analyzed from the two indicators of unconfined compressive strength and splitting strength. Besides, the internal mechanism of hydration products and strength formation of steel slag-blast furnace slag road base material under the lime activated were researched by XRD, SEM and thermogravimetric analysis. The strength test results show that when the mineral slag content is within 10% (mass fraction) and the mass ratio of lime and slag is between 1∶1 and 1∶2, the unconfined compressive strength and splitting strength of the mixed materials are higher than other lime and slag ratio at all ages. The microscopic test results reveal that an appropriate amount of Ca(OH)₂ can promote the hydration reaction rate of SiO₂ in the mineral slag, and improve the early strength of the composite material. In addition, the filling effect of the ettringite generated by the hydration reaction, fly ash and the inert components in the steel slag is also a favorable factor for the early strength growth of the material. The pozzolanic effect of fly ash and the continuous hydration reaction of C₂S in steel slag are contributed to the improvement of the later strength of the composite material.

Dense Filling Function of Superfine Slag Powder in Cement Particles

HUANG Fali, WANG Zhen, YI Zhonglai, CHENG Huan, WEN Jiaxin, YUAN Zhengcheng, JIN Hao, LI Huajian

2021, 40(8):  2647-2652. 

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Superfine slag powder can fill the porosity of cement-based materials and improve their microstructure and properties. The effect of superfine slag powder content on the bulk density of cement-superfine slag powder system was quantitatively analyzed by five test methods, including micro powder bulk density tester method, Puntke saturation point water consumption method, LCPC minimum water demand method, paste relative density method and water requirement ratio of standard consistency method. The test results of these five methods were compared with the Reschke theoretical values, the Andreasen equation-grey correlation analysis results and the Aim-Goff model predictive values. The results show that the bulk density values of cement-superfine slag powder system obtained by different tests or analysis methods are quite different. However, the tendency of the bulk density of cement-superfine slag system is basically the same as the content change of superfine slag powder. The paste relative density method and water requirement ratio of standard consistency are more sensitive to the change of bulk density of cementitious material system, which are more suitable for characterizing the bulk density of the cementitious material system. The predictive values of the Aim-Goff model are basically consistent with the test results, and the change of bulk density is more sensitive. It is suggested that the Aim-Goff model should be used to predict the change of the bulk density of the cementitious material system.

Experimental Study on Preparation of Sintered Brick from Fine Gold Tailings

DUAN Xuchen, MENG Fantao, WEI Chuncheng, LI Zhanchong, MU Qinglin, LIU Zhekun, WANG Yuliang

2021, 40(8):  2653-2658. 

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In order to solve the problem of environmental pollution and resource waste caused by the stockpiling of fine gold tailings, sintered bricks were prepared with fine gold tailings as the main raw material by adding bentonite and fly ash. The effects of sintering temperature, holding time and different proportion of materials on the properties of sintered bricks were studied. The results show that the optimal composition is 75% (mass fraction, same as bellow) of tailings, 15% of bentonite and 10% of fly ash. The optimum process conditions are 10% water content, 20 MPa forming pressure, 1 175 ℃ sintering temperature and 50 min holding time. The sintered bricks with compressive strength of 38.71 MPa, flexural strength of 10.54 MPa, volume density of 1.908 g/cm³, water absorption of 3.5% can be prepared by this process.

Morphological Characterization and Analysis of Recycled Brick Concrete Coarse Aggregate Particles

YANG Xiufen, HUANG Jiafu, DAI Dawang, YANG Chaojun, MENG Tao

2021, 40(8):  2659-2669. 

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In this study, the digital image processing technology was used to characterize the particle shape of the recycled brick concrete coarse aggregate. The distribution of characteristic parameters such as height width ratio, roundness and compact factor of each component was also analyzed. The experimental results show that the aggregate material is accurately identified through the color analysis, and the height width ratio, roundness and compact factor of the aggregate particles obtained based on the identification results have similar distribution rules. Among the four components of brick, stone, wood and ceramics, brick and stone account for a relatively larger proportion, and their characteristic parameters are also relatively similar, with less needle-like particles and better roundness, while wood aggregate is mostly needle-like particles with a larger height width ratio. Ceramics has the largest area and perimeter due to its higher strength. In addition, the gradation distribution of the brick and stone aggregates is basically a normal distribution, which can be mixed to form a well-graded aggregate. The research results are helpful to reveal the particle morphology characteristics of the recycled brick concrete coarse aggregate, and promote the research and application of the recycled brick concrete coarse aggregate.

Optimization of Mixture Ratio Research of Controlled Low Strength Materials Based on Response Surface Methodology

ZHU Youzeng, LIU Hao, HUANG Rui, ZHANG Peng

2021, 40(8):  2670-2679. 

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To solve the problem of low utilization rate of the recycled fine aggregate in concrete, the recycled fine aggregate was used to prepare controlled low strength materials (CLSM), and a new method for CLSM mixture ratio design was provided by response surface methodology (RSM). In this study, the water-solidratio, the content of polycarboxylic acid superplasticizer, the ratio of cement to the total cementitious material(pc/cm) were used as experimental factors, and the ratio of fluidity to bleeding rate and 28 d compressive strength were used as response values to conduct multi-index optimization. According to the single factor experiment, the increase of water-solid ratio and polycarboxylic acid superplasticizer content leads to the increase of CLSM fluidity and bleeding rate. With the increase of pc/cm ratio, the fluidity and the bleeding rate of CLSM gradually decrease. The results of dual response surface analysis show that the interaction of water-solid ratio and pc/cm ratio, polycarboxylic acid superplasticizer content and pc/cm ratio is significant on the ratio of fluidity to bleeding rate, while the interaction of the parameters on the 28 d compressive strength is not significant. Finally, by simultaneously optimizing the two response values, the optimal mixture ratio of CLSM is obtained, which is basically consistent with the actual results, and the multi-index optimization of CLSM working performance and compressive strength is realized.

Research on Properties of Recycled Concrete Prepared with Brick and Concrete Construction Waste

ZHANG Xianmeng, LIU Xu, BAI Bin, PENG Qian, JI Weiyi

2021, 40(8):  2680-2686. 

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Recycled coarse aggregate prepared from brick and concrete construction waste usually contains part of the brick aggregate. In order to study the failure mode and the influence of brick content on the properties of mixed recycled coarse aggregate concrete, the recycled concrete aggregate and brick aggregate were mixed in various proportions (volume fraction) to prepare mixed recycled aggregate, and the natural aggregate was replaced by mixed recycled aggregate in 30% to produce concrete specimens for test. The experimental results indicate that the natural aggregate in mixed recycled aggregate concrete fails along the interface transition zone between the aggregate and the mortar, while the recycled brick coarse aggregate is fractured through the aggregate. When the brick content is less than 18%, there is no obvious effect on compressive strength and resistance of chloride penetration, and once the brick content is more than 18%, compressive strength and resistance of chloride penetration decrease obviously. The higher the content of brick is, the worse the salt frost resistance of concrete is. When the brick content is constant, the higher the water cement ratio is, the smaller the adverse effect of recycled brick coarse aggregate on the compressive strength of concrete.

Ceramics

Preparation Methods and Research Status of Porous Ceramics

YUAN Qi, TAN Hua, YANG Tingwang, LU Wenlong, ZANG Jiadong, LI Haoyu, YAN Wenchao, ZHANG Shengwei, LU Ya, ZHANG Haibo

2021, 40(8):  2687-2701. 

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During the last decades, porous ceramics have been widely used in the fields of thermal insulation, gas filter, catalytic carrier, separation membrane, kiln furniture, biomedical substitutes, sensor materials and so on. The research on the preparation process and properties of porous ceramics shows a trend of rapid development, and a large number of innovative results were obtained. Based on the preparation process of porous ceramics, the development status and research results of five main preparation methods of porous ceramics were summarized, including partial sintering, sacrificial template, replica template, direct foaming and 3D printing. Meanwhile, the advantages and disadvantages of each preparation method and the direction of future development were also discussed, providing guidance and reference for the further development of porous ceramics.

Thermodynamic Growth Mechanism of SiC/C Fibers

YANG Fanfan, ZHANG Yu, ZHANG Tao, WANG Jian, ZHAO Wei, LI Jinyu, WANG Kun, LIU Yuhao, HAO Huanmin, FAN Lijun, HUANG Xiaoxiao, WEN Guangwu

2021, 40(8):  2702-2712. 

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The silica sol was diluted with ethylene glycol as diluent to obtain different concentrations of silica sol solutions, which were used as raw materials for coating commercial carbon fibers. After surface modification, the carbon fibers were coated with silica sol solution and held at 1 600 ℃ for 30 min in the Ar atmosphere. The silica sol coating and carbon fibers underwent carbothermal reduction reaction to form SiC coating. The morphology and structure of the products were characterized, and the growth kinetics and high temperature diffusion mechanism of SiC coating were studied according to thermodynamic data. The calculation results show that the reaction process is diffusion controlled. The SiC/C fibers have better oxidation resistance at high temperature than the carbon fibers, which provides a useful idea and thermodynamic basis for the low-cost preparation of new ceramic fibers.

Subcritical Hydrothermal Removal of Common Metal Impurity in β-SiC Powder

WANG Bo, DUAN Xiaobo, DENG Lirong, WANG Jiabo, LU Shuhe, WANG Xiaogang

2021, 40(8):  2713-2718. 

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High-purity β-SiC powders are used as raw materials for semiconductor wafers, semiconductor kiln furniture and ceramic devices used in semiconductor chip equipment. A subcritical hydrothermal method was used to remove metal impurities in β-SiC powders synthesized by high-temperature and high-pressure, which promotes the hydrothermal reaction. The removal effect of common metal impurities in β-SiC powders under different acid systems was studied. The content of trace elements was detected by inductively coupled plasma optical emission spectrometry spectrometry (ICP-OES), and the phase composition and microstructure of β-SiC powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results are as follows: the HCl system is better for Cr and Zr removal than the other two; the HCl+HF+HNO₃ system is better for Ca, Fe, Mg and Ti, and H₂SO₄+(NH₄)₂SO₄ system is better for Al and K. The best reaction temperature for treatment with HCl system is 200 ℃, the best reaction temperature for treatment with HCl+HF+HNO₃ system is 220 ℃, and the best reaction temperature for treatment with H₂SO₄+(NH₄)₂SO₄ system is 200 ℃. Among them, H₂SO₄+(NH₄)₂SO₄ system reduces the content of common metal impurities in β-SiC powders to the minimum, and the total content of impurities is 920.31 mg/L. Therefore, H₂SO₄+(NH₄)₂SO₄ system is the optimal scheme for β-SiC powders impurity removal.

Effect of La₂O₃ on Densification and Properties of Transparent Magnesium Aluminate Spinel Ceramics

LYU Simin, YANG Jinping, HAN Dan, LIU Mengwei, ZHANG Jian, WANG Shiwei

2021, 40(8):  2719-2725. 

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Transparent magnesium alumina spinel ceramics have both good optical and mechanical properties, and have broad practical and potential application prospects in the military and civilian fields. Due to its low densification rate, sintering aids are often introduced during the sintering process. Rare earth sesquioxides have high melting point and are not easily volatile at high temperatures. In recent years, some of them are used to promote the densification rate of magnesium aluminate spinel ceramics, but the sintering mechanism is still unclear. In this work, transparent magnesium aluminate spinel ceramics were prepared through pressureless sintering followed by hot isostatic pressing treatment, using high-purity commercial magnesium alumina spinel powders as the raw materials, and La₂O₃ as the sintering aid. XRD, SEM, UV-visible spectrophotometer and universal testing machine were employed to investigate the effect of La₂O₃ on the sintering and densification process of transparent magnesium aluminate spinel ceramics. The results show that La₂O₃ can result in lattice distortion through reaction with spinel or forming the solid solution at the high temperature, which promotes the densification process of spinel, and reduces the presintering temperature about 40 ℃. For samples subjected to hot isostatic pressing at 1 500 ℃/3 h at 190 MPa, La₂O₃ doping increases the transmittance in the ultraviolet region. At the same time, La segregates to the grain surface and inhibits the grain growth, which improves the mechanical strength of the sample. Compared with the undoped sample, the transmittance of 0.05% (mass fraction) La₂O₃ doped sample at 400 nm increases from 63% to 81%, its bending strength increases from 263.7 MPa to 319.0 MPa, and its fracture toughness increases from 1.69 MPa·m^1/2 to 1.82 MPa·m^1/2.

Foaming Properties of Ceramics Foamed by Polishing Slag System

DAI Yonggang, LU Chenglong, ZHANG Yinfeng, ZHANG Guotao

2021, 40(8):  2726-2733. 

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Foamed ceramics were prepared by commercially formula of polishing slag system, and the effects of sintering temperature on foaming properties of samples were studied. By contrastive analysis, the microstructure, linear shrinkage rate and volume expansion rate of samples with foaming agents were reseached, and the effects of pore structure on the strength and thermal stability were studied. It was found that, polishing slags can foam by itself, forming spherical pores with size of 10 μm to 200 μm (1 160 ℃ to 1 220 ℃). And the walls of pores were dense. It is very sensitive to sintering temperature, in the range of 1 180 ℃ to 1 200 ℃, the volume of the foamed ceramics sample expanded twice. The foaming property of samples with SiC was significantly improved, the pores were irregular, and the pore size of samples increased by 10 times. After adding foaming agent, There were small pores in the pore wall, which made the strength and the thermal conductivity loss less, while the porosity increased. However, the distribution of pores in the wall was uneven, decreasing the thermal stability of the foamed ceramics.

Glass

Influences of Melting Atmospheres on Content and Stability of Hydroxyl in Silica Glass

XIAO Peng, WANG Yufen, XIANG Zaikui, NIE Lanjian, WANG Lei, SHAO Zhufeng, FU Bo, JIA Yanan, WANG Hui, WANG Hongjie, RAO Chuandong, ZHANG Chenyang

2021, 40(8):  2734-2739. 

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Taking type Ⅲ silica glass as the research object, from the perspective of actual experiment and melting, the content and distribution of hydroxyl along the radial direction in silica glass under different melting atmospheres were explored. A preliminary analysis was made on the formation and stability of the hydroxyl. Experimental results show that distribution of hydroxyl in silica glass under different melting atmospheres is high in the middle and low in the edge along the radial direction, and the content of hydroxyl is the lowest in neutral atmosphere and the highest in reducing atmosphere. The long-term stoppage and empty burning method improves the situation that the silica glass yield is low in the original oxidizing atmosphere, but it leads to uneven surface of the ingot surface, and the edge hydroxyl content increases significantly. The hydroxyl content of silica glass in different melting atmospheres tends to be the same after high-temperature heat treatment, and the decrease rate is the largest under reducing atmosphere, about 55%.

New Functional Materials

Fabrication and Electrochemical Performances of Ga-Doped FeNb₁₁O₂₉ Materials

HUANG Jinping, CHEN Qing, LI Jianbao, LUO Lijie, CHEN Yongjun

2021, 40(8):  2740-2747. 

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FeNb₁₁O₂₉ is a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (400 mAh·g^-1). However, the reported practical capacities of FeNb₁₁O₂₉ are only 168 mAh·g^-1 to 273 mAh·g^-1. Therefore, it is very necessary to further improve the electrochemical performance of FeNb₁₁O₂₉. A simple and effective Ga-doped method was demonstrated in this study, which enhanced the electrochemical performances of FeNb₁₁O₂₉ materials successfully. XRD results show that Ga-doped doesn't change the orthogonal shear ReO₃ crystal structure of FeNb₁₁O₂₉. Scanning electron microscopy characterization indicats that no significant change in morphology is observed. Ga³⁺ could replace Fe³⁺ in FeNb₁₁O₂₉, the electronic conductivity of Ga_0.2Fe_0.8Nb₁₁O₂₉ is enhanced by two orders of magnitude compared with FeNb₁₁O₂₉. Consequently, Ga_0.2Fe_0.8Nb₁₁O₂₉ exhibits excellent electrochemical performances. At the current density at 0.1 C, the charge capacity of Ga_0.2Fe_0.8Nb₁₁O₂₉ reaches 290 mAh·g^-1, which remains 145 mAh·g^-1 when the current density rose to 5 C. Moreover, Ga_0.2Fe_0.8Nb₁₁O₂₉ presents outstanding cycling stability with a capacity retention of 91.0% at 5 C after 1 000 cycles. In contrast, undoped FeNb₁₁O₂₉ only possesses a charge capacity of 107 mAh·g^-1 with a capacity retention of 55.9% at 5 C after 1 000 cycles. The research indicates that the electrochemical performances of FeNb₁₁O₂₉improves significantly by Ga-doped, and Ga_0.2Fe_0.8Nb₁₁O₂₉ has wide application in LIBs in the future.

Synthesis and Photocatalytic Properties of SiO₂/g-C₃N₄ Composite Powders

XU Zezhong, ZOU Hui, CAO Xianzhi, WU Yang, HAN Chengliang

2021, 40(8):  2748-2754. 

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SiO₂/g-C₃N₄ composite powders were successfully prepared by calcination of proper as-prepared silicon dioxide (SiO₂) and melamine (C₃H₆N₆) composite precursors. The phase composition, morphology,optical absorption performance, and specific surface area of the composite powders were carried out by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), ultraviolet-visible light absorption spectrum (UV-Vis) andBET method. Results show that the average particle size of spherical SiO₂ prepared by modified Stöber method is about 200 nm and it has good dispersibility. When the content of SiO₂ is about 75% (mass fraction) in SiO₂/g-C₃N₄ composite powder, the specific surface area of composite powder is the largest, about 23.7 m²/g. At the same time, the photocatalytic properties of SiO₂/g-C₃N₄ composite powders with different g-C₃N₄ loading content were investigated under visible light irradiation with Rhodamine B and methylene blue as the target pollutants. Results indicate that with the decrease of the content of g-C₃N₄ in the composite powders, the visible light activity of the composite powder increases gradually. The composite powder with about 25% (mass fraction) g-C₃N₄ has the best photocatalytic degradation effect on Rhodamine B and methylene blue. The reason is that the strong absorption of composite powders enhances the visible light photocatalytic property.

Degradation of Tetracycline Hydrochloride by Bi₂MoO₆ Activated PMSunder Visible Light Irradiation

WU Deyong, SU Jishan

2021, 40(8):  2755-2762. 

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For treatment of antibiotic wastewater, the combined effect of semiconductor photocatalysis and sulfate radical (SO^-₄·)-based advanced oxidation processes is considered as a potential solution. Herein, 3D bismuth molybdate (Bi₂MoO₆) microspheres were prepared via a facile solvothermal method and applied to activate peroxymonosulfate (PMS) for tetracycline hydrochloride (TC) elimination under visible light irradiation. The morphology, crystal lattice structure, optical performance, and other properties of the Bi₂MoO₆ sample were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The result show that the 3D Bi₂MoO₆ microspheres with a size of ~1.5 mm are composed of Bi₂MoO₆ nanosheets with a thickness of ~20 nm. Bi₂MoO₆ microspheres exhibite high adsorption capacity and significantly photocatalytic performance for the degradation of TC under visible light illumination. Meanwhile, the addition of PMS enhances the ability of Bi₂MoO₆ microspheres for the degradation of TC under visible light illumination. The effects of catalyst dosage, PMS concentration, co-existing ions, such as chloride (Cl^-), carbonate (CO^2-₃) and nitrate (NO^-₃), and humic acids (HA) on the degradation of TC by Bi₂MoO₆ activated PMS under visible light irradiation were investigated through static experiments. Radical trapping tests suggeste that hydroxyl radical (·OH), sulfate radical (SO^-₄·), peroxy radical (O^-₂·), and hole (h⁺) all play a important role in the degradation of TC. Finally, the detailed photocatalytic mechanism was also proposed.

Finite Element Analysis on Effect of Needle Punching Parameter on Mechanical Properties and Thermal Conductivity of Basalt Fiber Preform

ZHENG Yun, QIAO Zhiwei, LIU Yanyou, NIU Bo, DUAN Wenjiu, ZHOU Guoxiang, YANG Zhihua

2021, 40(8):  2763-2769. 

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Needle punching parameter, such as needle density and needle depth, have a significant impact on the performance of the basalt fiber preform. Based on the finite element analysis method and the secondary development of ABAQUS software using Python language, the representative volume element (RVE) of the basalt fiber preform of different needle depth and needle density was established. The influence of these parameter on the mechanical properties and thermal conductivity of the basalt fiber preform were studied combined with the experimental results. The results show that the fiber mesh layer is mainly combined by needle punching fibers, and the shear performance of the prefabricated body can be improved by increasing the needle density and the needle depth, but the effect of increasing the needle density is more obvious than that of increasing the needle depth. When the temperature gradient is applied along the z-axis direction of the prefabricated body, the heat flow vector is mainly concentrated in the needle fibers, and the above phenomenon becomes more obvious when the needle depth is increased. Therefore, increasing the needle depth is not conducive to the thermal protection of the prefabricated body.

Preparation of SiO₂ Nanofiber Membrane by Electrospinning and Its Structure and Performance Optimization

SONG Yilong, ZHAO Fang, LI Zhizun, HUANG Hongjun

2021, 40(8):  2770-2776. 

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The optimization of the microstructure and mechanical properties of SiO₂ nanofibers was achieved by adjusting the composition of the electrospining method and the heat treatment process. In this paper, tetraethyl orthosilicate (TEOS) was used as raw material, polyvinylpyrrolidone (PVP) was used as spinning aid, and SiO₂ nano-membrane was prepared by electrospinning method combined with heat treatment process. The effects of polymer concentration and calcination rate on the microscopic morphology and mechanical properties of fiber membranes were studied. Using means of thermogravimetric and differential thermal analysis, X-ray diffractometer, fourier infrared spectrometer, scanning electron microscope and tensile testing machine, the fiber membrane was microscopically analyzed and tested. The results show that with the increase of PVP concentration, the morphology of the product develops from dice-shaped microspheres to continuous fibers, and the mechanical properties are improved accordingly. When the mass fraction of PVP is 25%, the fiber membrane has the best tensile strength, which is 3.25 MPa. With the increase of the heating rate, after the SiO₂/PVP continuous fiber membrane is calcined at 800 ℃, the residual thermal stress inside the product increases, the fiber continuity decreases, and the strength decreases. This research provides a theoretical basis for the functional application of SiO₂ nanofibers.

Prepration of Modified Fulvic Acid/Attapulgite Composites and Their Antimicrobial Properties

YANG Fangfang, ZHANG Qian, SONG Yameng, HUI Aiping, KANG Yuru, WANG Aiqin

2021, 40(8):  2777-2783. 

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Fulvic acid (FA) has the effect of inhibiting bacteria, anti-inflammation, and promoting animal growth. In order to further improve the broad-spectrum antimicrobial properties of FA, a composite was prepared by loading FA into attapulgite (APT) through the adsorption method, meanwhile cetyltrimethylammonium bromide (CTAB) was used to modify the composite. The results show that FA and APT are mainly combined by electrostatic adsorption, and the introduction of CTAB regulates the charge of FA/APT composites. The minimum inhibitory concentration (MIC) of the composites against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) decreases with the increase of CTAB amount. When the amount of CTAB is 15% (mass fraction), the MIC is 1 mg/mL for E. coli and the MIC is 0.05 mg/mL for S. aureus.

Road Materials

Salt Frost Resistance and Fatigue Characteristics of Self-Curing Pavement Concrete

QIN Xiao, XU Jieting, SHEN Aiqin, LYU Zhenghua, XIE Zhengzhuan

2021, 40(8):  2784-2793. 

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In order to improve the durability of pavement concrete effectively, the salt freeze-thaw test, fracture performance test before and after salt freeze-thaw cycles, and fatigue test for flexural load were conducted to explore the variation rule of salt frost resistance and fatigue characteristics of super absorbent polymer (SAP) self-curing pavement concrete with different SAP dosages and particle sizes. Combined with the pore parameters, microstructure, and the characteristics of the aggregate-cement interfacial transition zone (ITZ) of self-curing cement paste, the influence mechanism of performance was revealed. The results show that the residual pores formed by SAP with smaller particle size can effectively release the tensile stress, reduce the freezing point and refine the pore structure, which can enhance the salt frost resistance of pavement concrete. After 30 times freeze-thaw cycles, the fracture toughness loss rate and fracture energy loss rate of pavement concrete with SAP particle size of 100 mesh (150 μm) and content of 0.145%(mass fraction) decrease by 25.25% and 10.51% respectively, compared with the reference group. The enhancement degree of SAP to fatigue life increases with the increase of stress level. When the fatigue load stress level is 0.80, the fatigue life of pavement concrete is 2.65 times higher than the reference group. SAP can effectively improve the internal compactness of cement concrete structure, hold part of ITZ moisture, enhance the bonding between cement paste and aggregate, thus the salt frost resistance and fatigue characteristics of concrete are improved.

Influences of Aramid Fiber and Glass Fiber on Road Performance of Recycled Asphalt Mixture

ZHANG Rong, WANG Bin

2021, 40(8):  2794-2802. 

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To improve the road performance of the recycled asphalt mixture (RAP), aramid fibers and glass fibers were selected in the research, and the influences of the single mixing and compound mixing on the road performance of the recycled asphalt mixture was studied. The research results show that the single mixing aramid fiber has little effect on the high-temperature performance of the recycled asphalt mixture. The high-temperature rutting resistance of recycled asphalt mixture is increased by 34.0% and 42.6% by glass fibers and composite fibers, respectively. The improvement of dynamic modulus of recycled asphalt mixture by adding composite fibers is up to 21.9%. The addition of composite fibers makes the mixture maintain good low-temperature crack resistance and water stability. The semi-circular bending (SCB) test results show that the composite fibers can significantly improve the bending ability of asphalt mixing materials.Compared with single fiber, the composite fiber has better modification effect on recycled asphalt mixture, and the modification effect is significant.

Analysis of Damage Self-Healing Performance of Basalt Fiber Asphalt Concrete at High-Cold and High-Altitude Area

MA Haipeng, YU Pei

2021, 40(8):  2803-2810. 

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In order to explore the self-healing properties of basalt fiber asphalt concrete under different damage levels, freeze-thaw cycles, and ultraviolet radiation aging, afour-point bending fatigue test and scanning electron microscope were used to analyzefrom macro and micro angles.By comparing and analyzing the fatigue damage rate v_D and the cumulative dissipated energy E_CD before and after the specimen healing, the corresponding healing coefficient R_HI was obtained respectively. The conclusion shows that basalt fiber has improved damage self-healing properties of ordinary matrix asphalt concrete, and the maximum value of the damage healing coefficient is 96%. Under the same environmental factors, the damage degree of the test piece is inversely proportional to the healing coefficient. At the same degree of damage, the freeze-thaw cycle has the greatest impact on the healing performance of the test piece, and the damage healing coefficient decreases by up to 4%. Cumulative dissipated energy can be used as an analysis index to more accurately characterize the damage self-healing performance of asphalt concrete.Through scanning electron microscopy image analysis, the mechanism of the effect of basalt fiber on the self-healing performance of asphalt concrete before and after ultraviolet and freeze-thaw action was further microscopically explained.

Design and Road Performance of High Modulus Natural Asphalt Mixture

GUO Yinchuan, ZHANG Zhengming, SHAO Dongye, SHI Xiaopeng, WANG Lusheng, WANG Junmao

2021, 40(8):  2811-2821. 

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To explore the design method and road performance of high modulus natural asphalt mixture, the following works were done: high modulus natural asphalt HMB was selected, and high modulus natural asphalt mixture BBME-13 (béton bitumineux à module elevé-13) was prepared by modified Marshall design method. The Marshall volume index and internal structure of the asphalt mixture were analyzed, and the road performance differences of the asphalt mixture with SBS modified asphalt mixture SBSAC-13 and base asphalt mixture SKAC-13 were compared. The applicability of BBME-13 was verified by the construction of test section. The results show that the asphalt aggregate ratio, stability, and dynamic modulus of BBME-13 are significantly higher than those of SBSAC-13 and SKAC-13. The representative values of dynamic stability, residual stability and freezing breaking strength of BBME-13 are 32.2%, 9.0% and 45.5% higher than SBSAC-13, 148.3%, 19.6% and 93.2% higher than SKAC-13, respectively.The maximum flexural strain of BBME-13 is 3.3% less than that of SBSAC-13, and 34.4% more than that of SKAC-13. The pavement of BBME-13 test section has excellent impermeability, and its skid resistance and compactness can also meet the requirements of the specification.

Effect of Solid Waste Filler on Fatigue Property of Modified Asphalt During Aging Process

GUO Bingbing, JIA Xuemei, ZHANG Hengji, LIU Liyuan

2021, 40(8):  2822-2830. 

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To find the effect of adding solid waste filler on the fatigue property of modified asphalt, and then explore the effect of solid waste filler on the aging behavior of modified asphalt. This study used red mud, fly ash, diatomite and limestone powder to prepare four types of modified asphalt mortar. The fatigue properties of the original asphalt mortar and aged asphalt mortar were tested by linear amplitude sweep test (LAS), respectively. Four types of indicators were used in this article to evaluate the fatigue property of tested samples, including the damage accumulation (D(t)), integrity index (C(t)), strain sensibility (B) and fatigue life. Besides, the aging-fatigue decay index was selected in this study to indicate the negative effect of aging on asphalt mortar. The test results show that the addition of solid waste filler improves the fatigue property of modified asphalt during the aging process, namely, it enhances the aging resistance of modified asphalt. The level of improvement is listed from high to low as follows: diatomite, red mud, limestone powder, fly ash. Besides, adding solid waste filler not only hardens the asphalt but also fills the crack, both effects compete and determine the fatigue property jointly.