Table of Content

15 December 2023, Volume 42 Issue 12

Previous Issue    Next Issue

Cement and Concrete

Research Progress on Influence of Parent Concrete Strength on Properties of Recycled Aggregate and Recycled Aggregate Concrete

CHEN Chunhong, CHEN Yunchun, WANG Lei, YU Jiang, ZHU Pinghua, LI Haichao, XU Lingjie, WANG Cijian, QIAO Sen

2023, 42(12):  4183-4196. 

Asbtract ( 272 )   PDF (13876KB) ( 263 )  

References | Related Articles | Metrics

The use of recycled aggregate obtained from the crushing of construction solid waste can not only save natural sand and gravel resources, but also promote the recycling of construction solid waste. The quality of recycled aggregate determines the performance of recycled aggregate concrete. There are many factors affecting the quality of recycled aggregate, and the strength of parent concrete is one of the important influencing factors. The article takes strength of parent concrete as the research object, and summarizes its influence law on the properties of recycled aggregate and recycled aggregate concrete. Different strengths of parent concrete affect the quality and content of recycled aggregate adhesive mortar, which in turn affects the properties of recycled aggregate and recycled aggregate concrete. When the strength of parent concrete increases, the quality and content of adhesive mortar are improved. While the quality of adhesive mortar is improved, the properties of recycled aggregate and recycled aggregate concrete are strengthened. The increase in the content of adhesive mortar deteriorates the physical properties of recycled aggregate, increases the porosity and water absorption of recycled aggregate, but strengthens the internal curing effect of concrete, which contributes to the mechanical properties of recycled aggregate concrete. Using microscopic analysis, it is found that different strength of parent concrete make a difference in the content of hydration products in the interfacial transition zone of recycled aggregate concrete, which has an impact on the mechanical properties of concrete. The article provides a theoretical basis for further grading and utilization of recycled aggregate.

Optimal Design of Hybrid Fiber-Composite Cementitious Material System Based on Response Surface Methodology

LIU Ziyi, SONG Shaomin

2023, 42(12):  4197-4207. 

Asbtract ( 92 )   PDF (14123KB) ( 118 )  

References | Related Articles | Metrics

In order to overcome the disadvantage of poor mechanical properties of composite cementitious material system with large dosage, the response surface method was adopted to optimize the hybrid fiber composite cementitious material system, and the prediction model was established by taking the dosage of steel fiber, polypropylene fiber and desulphurization gypsum as the variable factors, and 28 d flexural strength and compressive strength of cement mortar as the evaluation indexes. Besides, the test of cement mortar and concrete was carried out to verify the predictive model. The results show that when the volume dosage of steel fiber is 0.4%, the volume dosage of polypropylene fiber is 0.116% and the mass dosage of desulphurization gypsum is 8%, the working and mechanical properties of composite materials reach the optimum, the predicted values of the 28 d flexural and compressive strength can be up to 7.0 and 37.4 MPa. The relative errors of flexural and compressive strength between the predicted values and the experimental values are only 2.86% and 1.32% and the standard deviation of the test values of flexural strength and compressive strength is 0.148 8 and 1.345 9, proving that the response surface method has high prediction precision, accuracy and scientificity. The optimisation effect of the composite cementitious material system is proved through this study, which provides a new solution idea and test basis for the multi-objective optimisation problem of composite materials.

Effect of Long-Term Low Temperature Environment on Microstructure and Mechanical Properties of Magnesium Oxychloride Cement

CHANG Chenggong, AN Lingyun, DONG Jinmei, ZHENG Weixin, WEN Jing, YAN Fengyun, XIAO Xueying

2023, 42(12):  4208-4215. 

Asbtract ( 84 )   PDF (7375KB) ( 115 )  

References | Related Articles | Metrics

In order to reveal the durability of magnesium oxychloride cement (MOC) under long-term low temperature environment, the effect of freezing time on microstructure, phase composition and mechanical properties of MOC samples were investigated by SEM, MIP, XRD, TG-DSC, FT-IR and microcomputer electro-hydraulic servo pressure testing machine. The results show that MOC samples have good long-term low temperature frost resistance. After 12 months of long-term low temperature freezing experiment, the weight of MOC samples only increases by 0.9%. The microscopic morphology changes from fine needle-like and gel-like to thicker needle-like and gel-like block. The microporous structure does not change significantly, with the average pore diameter varying between 38 and 48 nm and the pore volume distribution (0.01 μm to 0.1 μm) fluctuating from 70% to 80%. The phase composition does not change significantly, and the content of the main strength phase 5Mg(OH)₂·MgCl₂·8H₂O (5·1·8 phase) only decreases by 3%. The mechanical properties decrease slightly, in which the compressive strength decreases by 3.4 MPa and the flexural strength decreases by only 2.6 MPa.

Study on Effect of Aggregate Particle Size on Microstructure of Cement Mortar Based on Nuclear Magnetic Resonance Technology

LI Xian, NING Lin, CHEN Liangliang, LI Yang, DENG Xiaojiang

2023, 42(12):  4216-4223. 

Asbtract ( 63 )   PDF (4936KB) ( 85 )  

References | Related Articles | Metrics

In order to study the effect of aggregate particle size on the microstructure of cement mortar, the T₂ spectra, nuclear magnetic resonance (NMR) imaging hard pulse one-dimensional frequency coding technique (GR sequence) and permeability of standard cylindrical cement mortar samples with aggregates of standard sand and mechanized sand (particle sizes of 1.25~2.50 mm, 2.50~5.00 mm, and 5.00~10.00 mm, respectively) were measured by using a NMR device and the BRS-II impulse pore permeability detector. The effect of aggregate particle size on the pore size distribution, permeability, porosity, tortuosity, fractal characteristics of pore structure, and the uniformity of pore space distribution of cement mortar samples were investigated. The results show that the equivalent average pore radius and porosity of standard sand sample are the smallest. The equivalent average pore radius decreases first and then increases with the increase of aggregate particle size, while the aggregate particle size is negatively correlated with the tortuosity, and positively correlated with the permeability, porosity and fractal dimension of the capillary pores. In addition, with the increase of aggregate particle size, the unevenness of pore space distribution of sample increases significantly, and the aggregate particle size obviously affects the pore space distribution of cement mortar.

Effect of Superabsorbent Polymer on Properties of Engineered Cementitious Composites

LIU Jiabao, SHUI Zhonghe, QI Xibo, LI Shixiang, XIAO Xunguang

2023, 42(12):  4224-4232. 

Asbtract ( 53 )   PDF (10943KB) ( 83 )  

References | Related Articles | Metrics

Superabsorbent polymer (SAP) was added into engineered cementitious composites (ECC) slurry through two methods of non-soaked mixing and pre-soaked mixing, and the effects of SAP on the ultimate tensile strain, tensile strength, restrained shrinkage and toughness of ECC under different dosages and mixing methods were analyzed. The results show that non-soaked mixing significantly enhances the plastic viscosity and reduces the flowability of ECC slurry upon SAP addition. Conversely, the pre-soaked mixing method decreases plastic viscosity and improves flowability, facilitating the molding process of ECC slurry. The addition of SAP to ECC through the non-soaked mixing method exhibits higher initial cracking strength and tensile strength, along with better toughness. The addition of SAP to ECC through the pre-soaked mixing method results in increased ultimate tensile strain in ECC and a more effective improvement in the performance of shrinkage restraint. SAP significantly enhances the tensile strain capacity and toughness of ECC specimens. All ECC specimens with SAP exhibit favorable ductility, with ultimate tensile strain exceeding 3%. Compared to the control group, the ultimate tensile strain of ECC with SAP has increased by 62.0% to 99.0%.

Study on Compressive Mechanical Properties of Carbon Nanotube Cement-Based Materials Based on Acoustic Emission and DIC

LEI Longjian, HAO Yong, YUAN Man, DU Guofeng, YUAN Hongqiang, ZUO Qingjun

2023, 42(12):  4233-4241. 

Asbtract ( 38 )   PDF (9686KB) ( 74 )  

References | Related Articles | Metrics

In order to study the influences of carbon nanotubes (CNTs) on compressive mechanical properties of cement-based materials, uniaxial compressive test was conducted on cement-based materials with different of CNTs content (0%~1.0%, mass fraction), and acoustic emission (AE) and digital image correlation method (DIC) were used for whole process monitoring. The results show that with the addition amount of CNTs, the compressive strength of specimen increases first and then decreases. The compressive strength of specimen reaches the maximum value when the content is 0.6%, which is 23.6% higher than that of control group. When the content of CNTs is 0.8%, the compressive strength of specimen is 10.6% lower than 0.6% CNTs group and 10.5% higher than that of control group. The ringing count and energy change are in good agreement with stress-strain curve of specimen during loading. The ringing count and energy sudden increase can be used as early warning basis for the damage and failure of specimen. The strain value in loading stage increases first and then decreases with the increase of CNTs content, and the specimen with low compressive strength first shows obvious strain changes. The main strain cloud diagram is mainly axial distribution, indicating that the failure mode of specimen surface is mainly vertical splitting.

Bending Performance of BFRP Bars Alkali-Activated Sea Sand Concrete Beams

FAN Xiaochun, CUI Qi, ZHANG Ao, WANG Wenqi

2023, 42(12):  4242-4253. 

Asbtract ( 44 )   PDF (9211KB) ( 79 )  

References | Related Articles | Metrics

In this paper, a new type of material structural member of basalt bar alkali-activated sea sand concrete (BASC) beam was proposed. In order to study the bending performance of BASC beams, five concrete beams were fabricated. The effects of basalt fiber reinforced polymer (BFRP) reinforcement ratio and different reinforcement types on the bending performance and failure modes of alkali-activated sea sand concrete (ASC) beams were studied. The test results show that the increase of the reinforcement ratio of BASC beams has little effect on the cracking load, but it can effectively improve its ultimate load. Taking the reinforcement ratio of 0.27% as the reference group, when the reinforcement ratio increases to 0.48%, 0.75% and 1.08%, the ultimate bearing capacity of BASC beams increases by 109.46%, 119.60% and 189.66%, respectively. Compared with ordinary steel bars, the elastic modulus of BFRP bars is smaller. With the same reinforcement ratio, the cracking load of ordinary steel bar ASC beams is 50%, larger than that of BASC beams. The theoretical calculation models of bending capacity, maximum crack width and deflection of normal section are proposed. Due to the influence of chloride ion diffusion in ASC, the calculation model needs to be modified. The calculated values of BASC beams after fitting are in good agreement with the experimental values, which can provide reference for the application of BASC beams in ocean engineering.

Experimental Study on Performance of Reinforced Sand Aerated Concrete Materials

REN Jintao, HU Rongrong, HUANG Wei, QUAN Wenli

2023, 42(12):  4254-4261. 

Asbtract ( 51 )   PDF (7671KB) ( 68 )  

References | Related Articles | Metrics

On the basis of ordinary sand aerated concrete, the reinforced sand aerated concrete was prepared with gold tailing sand as silica material and basalt fiber and aerogel as reinforcing materials. The effects of basalt fiber content, basalt fiber length and aerogel content on performance of reinforced sand aerated concrete were analyzed. The results show that with the increase of basalt fiber content (0.1%, 0.2%, 0.3%, 0.4%, mass fraction) and basalt fiber length (3, 6, 9, 12 mm), the dry density, compressive strength, flexural strength and thermal conductivity of sand aerated concrete increase. The optimal content of basalt fiber is 0.3% and the optimal length of basalt fiber is 6 mm, at which time the compressive strength increases by 9.64% than that without fiber, the flexural strength increases by 21.42% than that without fiber, the mechanical properties are better, and the thermal conductivity is less affected. The optimal content of aerogel is 1.5%, at which time the thermal conductivity is reduced by 10.68%, and the compressive strength and flexural strength are slightly reduced, but still meet the relevant strength requirements.

Effect of Foam Content on Performance of Ultra-Lightweight Magnesium Oxysulfate Foamed Concrete

LYU Xiating, TAN Hongbo, ZHANG Shixuan, LI Maogao, WANG Jintang, JIAN Shouwei

2023, 42(12):  4262-4270. 

Asbtract ( 61 )   PDF (12302KB) ( 95 )  

References | Related Articles | Metrics

Magnesium oxysulfate cement has the advantages of light weight, low thermal conductivity and fire resistance, so it has great market potential to be prepared as foamed concrete and applied in building exterior insulation system. The density of ultra-lightweight magnesium oxysulfate foamed concrete was regulated by incorporating high stability modified foam. The changes in pore structure were investigated through scanning electron microscope (SEM) and optical microscope (OM). Additionally, the effects of density and pore structure variations on the compressive strength and thermal conductivity of ultra-lightweight magnesium oxysulfate foamed concrete were also studied. The results indicate that with the increase of content of high stability modified foam, the number of pores increases and the average pore size significantly decreases. The density of ultra-lightweight magnesium oxysulfate foamed concrete decreases gradually, and the compressive strength gradually decreases as well. When the foam content is 250% (mass fraction), the density of ultra-lightweight magnesium oxysulfate foamed concrete reduces to 88.33 kg/m³, and the thermal conductivity reduces to 0.038 2 W/(m·K).

Finite Element Nonlinear Analysis of Axial Compression Performance of Recycled Concrete Composite Columns with Square Steel Tubes

GAO Jinlong, LI Ming, ZHOU Qi, NIU Haicheng, ZHAO Pengpeng, HE Huanhuan

2023, 42(12):  4271-4282. 

Asbtract ( 40 )   PDF (8246KB) ( 60 )  

References | Related Articles | Metrics

To study axial compression performance and nonlinear mechanical performance of recycled concrete composite columns with square steel tubes, based on the axial compression performance test of recycled concrete composite columns with square steel tubes, a refined model of composite columns was established by using nonlinear finite element software ABAQUS, and its axial compression performance was analyzed by nonlinear numerical model. On this basis, the effect of recycled aggregate concrete strength grade, tie bar spacing, stirrup spacing, square steel tube wall thickness and slenderness ratio on axial compression performance of composite columns were further expanded and analyzed. The stress strain nephogram and load-displacement curves of composite columns were obtained. The results show that the experimental results are basically consistent with numerical simulation results, which also verifies the rationality of finite element model of composite columns. At the end of loading, the middle part of composite columns is damaged by bulging, which shows that the protective layer of recycled concrete is crushed and falls off, the steel bars and steel tubes are locally bulging, and the core recycled concrete is crushed. With the increase of strength grade of recycled concrete, the bearing capacity and energy dissipation of composite columns gradually increase. Setting tie bars can significantly improve the bearing capacity and energy dissipation of composite columns, but the ductility is only slightly improved. The bearing capacity, ductility and energy dissipation of composite columns decrease with the increase of stirrup spacing and slenderness ratio. With the increase of the wall thickness of square steel tubes, the bearing capacity, deformability and energy dissipation capacity of composite columns are significantly enhanced.

Mix Ratio Optimization and Comprehensive Evaluation of PVA/Steel HFRCC Based on PCA

WANG Rui, ZHANG Pinle, HU Jing

2023, 42(12):  4283-4297. 

Asbtract ( 36 )   PDF (6428KB) ( 59 )  

References | Related Articles | Metrics

The mechanical properties of hybrid fiber reinforced cementious composites (HFRCC) can be better brought into play when steel fiber, domestic PVA fiber and Japanese Corari PVA fiber are prepared according to the appropriate proportion, which is beneficial to cost control and has a wide application prospect. The influences of steel fiber volume content, domestic PVA fiber on the replacement rate of Nissan PVA fiber (volume fraction, same below) on the tensile strength, compressive strength and bending strength of HFRCC were analyzed by factor optimization method and principal component analysis (PCA). Through the principal component analysis of HFRCC, the mathematical model of comprehensive performance evaluation was established, and the multi-objective optimization was carried out. The results show that the maximum increase of tensile strength, compressive strength and bending strength of HFRCC is 61.04%, 31.30% and 78.57% respectively. When the steel fiber content is 0.2%~0.4% and the domestic PVA fiber volume replacement rate is 50%~100%, the maximum cost reduction is 88.25%, and the HFRCC strength index can reach the best. The weight proportion of each factor affecting HFRCC performance is as follows: domestic PVA fiber content, Nissan PVA fiber content and bending strength account for 46.28%. The content, compressive strength and bending strength of steel fiber account for 25.58%. The content and tensile strength of steel fiber account for 22.25%. Combined with variable correlation analysis, these indicators should be focused on when performance optimization based on HFRCC. The results can provide a basis for the preparation of HFRCC.

Analyzing Methods for Stability and Homogeneity of Self-Compacting Concrete Based on Rheological Parameters of Multiple Samples Statistics

WEI Qiang, GAO Qiang, LU Fuzhou, CHEN Liangsheng, CHEN Ben, ZHAO Guoxin, LI Jing, CHEN Zheng

2023, 42(12):  4298-4308. 

Asbtract ( 49 )   PDF (4188KB) ( 62 )  

References | Related Articles | Metrics

Self-compacting concrete with high fluidity and compactness is often used in the special engineering structures such as concrete-filled steel tubes. However, its preparation and construction process are highly susceptible to complex factors at the engineering site, resulting in uncontrollable fluctuations in its workability. There is still a lack of analytical control methods based on essence of rheology. This paper makes an analysis of the rheological parameters of concrete according to the data collected from actual engineering sites. The results show that the rheological parameters of concrete well conform to a log-normal distribution under multiple sample conditions. Besides, an analysis of the overall concrete stability was carried out according to the 95% confidence interval of the samples, using $\bar{\tau}$_s0∈[194.75,225.76]∩$\bar{\mu}$∈[88.76,95.00] as a criterion for good concrete stability, and the rheological parameters of concrete adjusted on site were analyzed along with the flow behavior of concrete in the pump pipe. The direction of rheological property regulation was discussed, and methods for optimizing pumpability ranges (τ_s0=[54.17,391.76]∪μ=[52.77,126.66]) and rheological parameters were proposed based on concrete rheological parameters. By revealing the inherent homogeneity of the concrete through the analysis of the characteristics of the rheological parameter curves, the paper proposed a criterion for the homogeneity evaluation of self-compacting concrete on site, providing a theoretical basis for the homogeneity evaluation, rheological property regulation and mix proportion design of self-compacting concrete.

Mix Proportion and Performance of Delayed Setting Bag Grouting Filler

DENG Junrong, SU Dong

2023, 42(12):  4309-4322. 

Asbtract ( 39 )   PDF (18869KB) ( 64 )  

References | Related Articles | Metrics

In order to develop a new type of bag grouting filler, cement-bentonite was used as main filling material. On the basis of studying the influence of single doped triethanolamine (TEA), codoped TEA and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) on the performance of the filler, through orthogonal test, the effects of five factors, namely water cement ratio, bentonite content, HEDP content and polycarboxylate superplasticizer (PCE) content and TEA content on the performance of the filling material were studied, and the best mix ratio of the filler was determined. Finally, the microstructures were analyzed by XRD, LF-NMR and SEM testing methods. The results show that TEA can optimize the pore structure of the filler and improve its early strength, bentonite can significantly reduce the bleeding rate of the filler, HEDP can significantly delay the initial setting time of the filler, and PCE can enhance the fluidity of the filler. The optimal proportion of filler is water cement ratio 0.9, bentonite 8%(accounts for cement mass fraction, the same below), HEDP 0.15%, PCE 1.0%, TEA 0.02%. The initial setting time of the optimized filler is 138.42 h, and the 7 d compressive strength is 5.7 MPa.

Interfacial Bonding Performance of BFRP Composite Cement Board and PUR Insulation Board

SONG Xiaoruan, HUANG Song, GAO Rui, LUO Shili, GAO Yijing

2023, 42(12):  4323-4331. 

Asbtract ( 47 )   PDF (8800KB) ( 72 )  

References | Related Articles | Metrics

With the proposal of "dual carbon" goal, all kinds of new composite thermal insulation formwork and integrated composite wall have become the current research hotspot. A composite thermal insulation formwork with rigid polyurethane (PUR) insulation board as insulation layer and basalt fiber reinforced polymer (BFRP) composite cement board as surface layer was proposed. Six sets of specimens were designed for push-out shear test. The effects of groove type, depth and number on the interfacial bonding performance between surface layer and insulation layer were studied. The energy dissipation factor was introduced to evaluate the energy dissipation capacity of specimens. The results show that grooving on the insulation board, deepening the grooving depth and increasing the number of grooving can improve the interfacial bonding strength and toughness of the specimen. Comprehensive comparison of various working conditions, grooving on the surface of PUR insulation board can significantly improve the interfacial bonding performance of the specimen. The interfacial bonding performance of the transverse groove specimen is better than that of the longitudinal groove specimen. The "#"-shaped groove specimen makes that the interfacial bonding strength, toughness and energy dissipation capacity of specimen increase by 164%, 286% and 28.57%, respectively, compared with the unslotted specimen, showing the best interfacial bonding performance. Deepening the grooveing depth has limited improvement on the interfacial bonding performance and has little effect on the energy dissipation capacity. Increasing the number of grooving can improve the interfacial bonding performance of specimen by about 16%. Through regression analysis, the calculation formula ofinterfacial bonding strength was established, and compared with the experimental results, the calculated values are in good agreement with the experimental values.

Solid Waste and Eco-Materials

Research Progress on Effect of Steel Slag on Durability of Plateau Concrete

BAI Qing, DENG Wei, LU Fuyang, ZHAI Jianliang, LAI Hao, MAO Nan, SHI Changchun, XIONG Rui

2023, 42(12):  4332-4340. 

Asbtract ( 84 )   PDF (10761KB) ( 115 )  

References | Related Articles | Metrics

The extensive accumulation of steel slag poses a severe threat to ecological environment. Utilizing steel slag in concrete effectively enhances the utilization rate. Under the coupling effect of low pressure and drying, the low activity problem restricts the application and development of steel slag in plateau concrete. This study focuses on the unique characteristics of plateau climate and comprehensively reviews the impact of steel slag on the frost resistance, salt erosion resistance, and shrinkage resistance of plateau concrete. Additionally, it analyzes the properties of steel slag and summarizes the challenges associated with using steel slag as an admixture and aggregate. Through a thorough analysis of existing research, we find that appropriate pretreatment of steel slag and the addition of suitable mineral admixtures can enhance the reactivity of steel slag, promote the development of more compact concrete structures, and improve the applicability of steel slag in plateau concrete.

Review on Recent Developments of RecyclingWaste Wind Turbine Blades

ZHANG Zhaozhen, JIN Xiaodong, SUN Shibing, TIAN Yingliang, ZHAO Zhiyong, LI Peixin, YAN Huajian

2023, 42(12):  4341-4350. 

Asbtract ( 87 )   PDF (4038KB) ( 91 )  

References | Related Articles | Metrics

Wind energy is an important clean energy, according to China’s carbon peak and carbon neutral strategy, the policy of replacing small with large wind turbine blades and replacing old with new is imperative. The main material of wind turbine blades is glass fiber reinforced polymer, which has problems of difficult recycling technology and high recycling cost. Nowadays, there is no ideal large-scale recycling method. Therefore, the systematic and high-value utilization of waste wind turbine blades is imminent. In this paper, the material type, recycling methods and their respective characteristics of wind turbine blades are summarized. The recent developments of waste wind turbine blades in cement-based materials and thermoplastic polymer materials are thoroughly discussed. Overall, this paper can provide reference for the subsequent development and research on the recycling waste wind turbine blades.

Application of Metakaolin in Artificial Hydraulic Lime Repair Mortar

GU Lilong, SHANG Huaishuai, WU Yayue, MENG Weiguang, HOU Guanhao

2023, 42(12):  4351-4359. 

Asbtract ( 54 )   PDF (8058KB) ( 69 )  

References | Related Articles | Metrics

In order to prepare a green inorganic restoration material that is suitable for the restoration of historical buildings, based on the XRD test results of the bonding materials of several historical brick masonry buildings in Qingdao, an artificial hydraulic lime repair mortar was prepared by mixing metakaolin. The influence of metakaolin on the artificial hydraulic lime mortar was studied by testing the fluidity, setting time, mass loss rate, dring shrinkage rate and mechanical properties. The results show that metakaolin can reduce the fluidity, shorten the setting time, reduce the dring shrinkage rate and improve the compressive strength and bonding strength of artificial hydraulic lime mortar. When the content is 5.0% and 7.5% (mass fraction), the 56 d compressive strength of artificial hydraulic lime mortar increases by 66.8% and 94.3%, and the bond strength increases by 22.2% and 25.9%. Finally, XRD and SEM were used to test and analyze the microstructure of the materials. The results show that the main reason for the improvement of the performance of the artificial hydraulic lime mortar by metakaolin is that the active SiO₂ and Al₂O₃ in metakaolin react directly with the lime, and consume Ca(OH)₂, which promotes the hydration of cement and enhances the bonding force between the hydrated products and the aggregate.

Autogenous Shrinkage Performance Evolution Law of Mortar Mixed with Granite Powder

CHEN Mei, HAN Yixuan, ZHANG Yunsheng, HU Xiangnan, XUE Cuizhen, WANG Jianghua

2023, 42(12):  4360-4367. 

Asbtract ( 40 )   PDF (5702KB) ( 59 )  

References | Related Articles | Metrics

In order to improve the utilization rate of granite powder, based on the analysis of the influence of grinding time on particle characteristics of granite powder, the influences of granite powder dosage and grinding time on autogenous shrinkage performance of mortar were systematically studied. The main factors affecting the self shrinkage performance of mortar with granite powder were analyzed using grey entropy method. Finally, microscopic testing methods were used to reveal the mechanism of the influence of granite powder on self shrinkage performance of mortar. The result show that with the increase of grinding time, the fineness of stone powder particles gradually increases, the content of particles with a particle size less than 10 μm increases, the content of particles with a particle size greater than 40 μm decreases, and the self-contraction deformation of granite-doped stone powder mortar gradually increases. With the increase of granite powder content, the self shrinkage deformation of mortar shows a pattern of increasing first and then decreasing. Appropriately reducing the dosage of granite powder particles with particle size less than 20 μm is beneficial for improving the self shrinkage activity index of mortar mixed with granite powder. The granite powder mainly affects the type and quantity of hydration products inside mortar, thereby affecting its self shrinkage deformation law.

Mix Ratio Optimization Design and Synergistic Effect Study of Multi-Source Solid Waste Binders

ZHU Zengchao, LIU Xianping, SHUI Zhonghe, GAO Xu, HUANG Yun, ZHENG Wu, GE Yexin

2023, 42(12):  4368-4377. 

Asbtract ( 72 )   PDF (6689KB) ( 100 )  

References | Related Articles | Metrics

The synergistic preparation of multi-source solid waste binders (MSSWB) using multiple solid wastes is an effective way to utilize solid waste resources. However, the relatively complex raw material composition and low mechanical properties limit the application of MSSWB. 100 sets of experimental mix ratios were designed as a data set with the help of D-optimal design method, then PSO-BP was created model for the prediction of the mechanical properties of MSSWB, and the optimal mix ratios of each raw material were determined by particle swarm optimization algorithm (PSO), and finally the hydration products of MSSWB products and the synergistic effect between multiple solid wastes were investigated by microscopic analyses such as XRD, TG-DTG and NMR. The results show that the PSO-BP model can effectively predict the compressive strength of binders, and the mix ratio strength after optimization by the particle swarm optimization algorithm is significantly higher than that of the unoptimized mix ratio strength, the 28 d compressive strength of the cementitious sand in the optimal mix ratio group is 20.8% higher than that of the unoptimized ratio group. The formation of the higher strength in the optimized mix ratio group is mainly related to the higher generation of hydration products of ettringite (AFt) and C-S-H gels. The formation of higher strength in the optimized mix ratio group is mainly related to the higher generation of the hydration products AFt and C-S-H gel and the higher cross-linking degree between the hydration products. This proves that the synergie is even more pronounced when the ratios of the raw materials are optimised.

Preparation of Cement Clinker from Red Mud Reduction Iron Recovery-Dealkalization Tailings

WANG Yali, LI Yiyang, WANG Lingyu, DING Sizhe, YAO Yuhan

2023, 42(12):  4378-4388. 

Asbtract ( 89 )   PDF (15997KB) ( 150 )  

References | Related Articles | Metrics

There are too much iron and alkaline in red mud, which hinders its utilization in cement. In order to enhance the reusing rate of red mud in cement material, this research paid adequate attention on reduction methods for iron recovery from red mud, water heated ion-exchanging methods using calcium carbide slags and oxalic methods for dealkalization of red mud, eventually used refactored red mud after iron recovery and dealkalization to prepare cement clinker. The results show that under the optimized condition that the sintering temperature is 1 400 ℃, lasting time is 1 h, rice husk ash adding content is 9.08% (mass fraction), cooling method is water cooling, the iron recovery rate of red mud is 77.24% while the content of iron declines to 9.39% (mass fraction) after iron recovery. Under the condition that reacting temperature is 90 ℃, deironed red mud and calcium carbide slags mass ratio is 1:1, liquid to solid rate (mL/g) is 6, reacting time is 7 h, the dealkalizaiton rate of ion exchanging methods using calcium carbide slags is 89.30%, meanwhile, the content of Na₂O in refactored red mud drops to 0.592% (mass fraction), which meets the requirement for cement ingredients that alkaline content must be lower than 1%. When the rate value of cement raw material, namely the lime saturation factor is 0.88, silicon rate factor is 2.4, aluminum rate factor is 1.4, cement raw materials prepared using refactored red mud possess good burnability under the sintering temperature ranging from 1 300 ℃ to 1 450 ℃. When the sintering temperature is 1 350 ℃, grains in cement clinkers show as irregular polygons with normal morphology. Accordingly, the optimum sintering temperature for cement clinker preparation adding refactored red mud is 1 350 ℃.

Effect and Mechanism Analysis of Slag Content on Shrinkage and Compressive Strength of Thermal Curing Fly Ash-Based Geopolymer

GUO Hongli, BAI Pengxiang, HONG Miao, ZHU Feipeng, HU Feng, LEI Dong

2023, 42(12):  4389-4398. 

Asbtract ( 46 )   PDF (24105KB) ( 61 )  

References | Related Articles | Metrics

The effects of six slag dosages of 0%, 10%, 20%, 30%, 40% and 50% (mass fraction, the same below) on the shrinkage of fly ash-based geopolymer (FAGP) concrete during thermal curing process were studied with digital image correlation (DIC) method. The compressive strength of concrete and paste after thermal curing were tested, and the microscopic mechanism was analyzed by combining simultaneous thermal analysis (TG-DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that with the increase of slag content, the total shrinkage and shrinkage rate of FAGP first decrease and then increase, the compressive strength increases first and then decreases, the hydration degree increases, and the number of microcracks increases. When the slag content is 40%, FAGP concrete has the smallest shrinkage and the highest compressive strength. When the slag content is low, the hydration degree of the geopolymer is small, and there are fewer microcracks. At this time, the main reason for the shrinkage of the geopolymer is the lower elastic modulus at the beginning of thermal curing. When the slag content is high, the hydration degree of the geopolymer is high, and there are many microcracks. At this time, the shrinkage deformation of the geopolymer is mainly caused by a large degree of chemical reaction.

Study on Impact Resistance of Steel Slag Fine Aggregate Concrete Based on Drop Hammer Impact Test

LIU Qiuyu, XUE Gang, TAN Junqing, LI Jingjun

2023, 42(12):  4399-4407. 

Asbtract ( 46 )   PDF (4920KB) ( 64 )  

References | Related Articles | Metrics

To investigate the impact resistance of steel slag fine aggregate concrete, the concrete specimens were prepared by replacing fine aggregate with equal volume of steel slag at replacement rates of 10%, 20% and 30%, respectively. The impact resistance test was carried out by drop hammer impact device to study the impact life and damage evolution law, and the impact resistance of specimen was compared with ordinary concrete. The results show that the addition of steel slag fine aggregate can improve the impact resistance of concrete, and the impact life is obviously improved when the drop weight is small. There is a certain degree of dispersion in the results of concrete impact resistance test, and the impact life of steel slag concrete conforms to Weibull distribution. Based on the Weibull distribution, the impact life under different failure probabilities is estimated, and the impact damage evolution equation is established to calculate the corresponding impact times when the concrete with different steel slag content reaches a certain damage variable.

Hydration Process and Long-Term Strength of Gypsum Slag Cement with High Content of Phosphogypsum

LIAO Yishun, WANG Kai, LI Hao

2023, 42(12):  4408-4415. 

Asbtract ( 89 )   PDF (9453KB) ( 130 )  

References | Related Articles | Metrics

A large amount of phosphogypsum, ground granulated blast-furnace slag and slaked lime were employed to prepare the gypsum slag cement. The effect of phosphogypsum content on the hydration process and long-term strength of gypsum slag cement was investigated through hydration heat, chemical shrinkage, pH value of pore solution and compressive strength tests, combined with XRD and SEM-EDS. The results show that the third peak of heat release curves of cement pastes gradually decreases when the phosphogypsum content increases from 40% to 70% (mass fraction, the same below). The chemical shrinkage at 14 d increases from 0.066 mL·g^-1 to 0.193 mL·g^-1, and chemical shrinkage rate significantly increases during the early hydration stage (0~1 d). The pH value of pore solution tends to stabilize within 28 d. Compared with 28 d compressive strength, the 90 d compressive strength is enhanced by 12.3%~27.8%. XRD and SEM-EDS reveales that the cement pastes mainly consists of gypsum, quartz, ettringite and C-S-H gel. At the age of 28 d, the ettringite content decreases from 7.48% to 2.84%, and the Ca/Si ratio (molar ratio) of C-S-H gel increases from 1.08 to 2.24 with the increase of phosphogypsum.

Heat Conduction and Strength Characteristics of Phosphogypsum-Based Foamed Building Gypsum

XUE Kaixi, SI Pengchao, WANG Tianyuan, CAI Mengying, CHU Yixin, HU Yanxiang

2023, 42(12):  4416-4426. 

Asbtract ( 52 )   PDF (3428KB) ( 74 )  

References | Related Articles | Metrics

In order to further improve the comprehensive utilization rate of phosphogypsum, this article used a single factor experiment to study the effect of the dilution ratio of the composite foaming agent solution with a mass ratio of AOS, animal protein and K12 at 1:1:1 on the porosity and pore structure of phosphogypsum-based foamed building gypsum. And the relationship between porosity and strength, thermal conductivity was studied. The research results show that when the apparent density is between 600 kg/m³ and 800 kg/m³, the thermal performance of phosphogypsum-based foamed building gypsum is better than that of the other four groups of foam insulation materials. When the apparent density is greater than 900 kg/m³, the compressive strength is much higher than that of the other gypsum-based foam materials. The relationship between thermal conductivity and porosity is consistent with the Maxwell-Euchen1 model, while the relationship between compressive strength and porosity is more consistent with the Hasselmann equation. This study provides data support for the production of phosphogypsum-based foamed building gypsum.

Dynamic Characteristics of Cement-Phosphogypsum Improving Peaty Soil

QU Juntong, LUAN Kaiyu, PU Junxiang, WANG Wenbin, LONG Ningbo

2023, 42(12):  4427-4437. 

Asbtract ( 40 )   PDF (4204KB) ( 52 )  

References | Related Articles | Metrics

In order to study the effect of cement-phosphogypsum comprehensive improvement on the dynamic characteristics of peaty soil in Dianchi area of Kunming, the laboratory dynamic triaxial test of improved peaty soil with different content of cement and phosphogypsum was carried out based on the previous laboratory test results. The effects of dynamic response and strength characteristics under different confining pressures, loading frequencies, dosages, consolidation ratios and dynamic stress amplitudes were mainly studied. The hysteresis curve change law at N=6 vibration level and the results of XRD test were analyzed. The results show that the dynamic characteristics of improved peaty soil change greatly. On the basis of separately adding cement as the main modifier, the stiffness and elasticity have been slightly improved. After adding phosphogypsum as an admixture, the combined effect is more obvious, the deformation resistance is improved significantly, the energy dissipation ability of soil is reduced, and the hysteresis curve has an obvious tendency to deflect to the longitudinal axis, which indicates that compared to the single action of cement, the composite action of cement-phosphogypsum has a more significant improvement effect on the soil stiffness and elasticity of the improved peaty soil, greatly improving the seismic performance. The improved peaty soil can be better applied to relevant practical engineering.

Experimental Study of Alkali-Activated Geopolymer Cured Silty Soil Based on Response Surface Method

LI Sheng, ZHANG Hongri, WANG Guiyao, DENG Renrui

2023, 42(12):  4438-4448. 

Asbtract ( 45 )   PDF (11315KB) ( 57 )  

References | Related Articles | Metrics

In order to achieve the resource utilization of beach silty soil and industrial wastes, and quantitatively optimize the critical factors of geopolymer cured silty soil, the mix ratio of alkali-activated slag-fly ash based geopolymer cured silty soil was optimized based on the Box-Behnken response surface method. The slag content, alkali activator modulus and alkali activator content were selected as the main factors to be investigated, and the curing mechanism was analyzed by combining the macroscopic properties and microscopic morphology. The results show that: the optimum mix ratio of cured soil is slag content 86.5% (mass fraction), alkali activator modulus 0.84, alkali activator content 7.3% (mass fraction), the unconfined compressive strength of cured soil at 7 and 28 d under the optimum mix ratio is 5 823 and 7 027 kPa, respectively. The prediction value has a small error with the actual value, and the established model is accurate and reliable in fitting the actual data. The hydration products of cured soil are mainly amorphous gel hydrated calcium silica-aluminate (C-(A)-S-H) and silica-aluminate polymer (N-A-S-H), which enhance the densification and skeletal structure of soil body, thus improving the strength of cured soil. This study provides a theoretical basis and experimental foundation for alkali-activated geopolymer cured silty soil.

Influence of Calcium Carbide Slag-Desulfurization Ash on Basic Properties and Microscopic Characteristics of Fluid Solidified Soil

BAO Yijun, WANG Ningning, LI Shujin, WU Wenwen, CHEN Xudong, ZHANG Wenwen

2023, 42(12):  4449-4455. 

Asbtract ( 67 )   PDF (4767KB) ( 63 )  

References | Related Articles | Metrics

The basic performance indexes of fluid solidified soil include wet density, bleeding rate, flow value and compressive strength. In order to explore the influence of calcium carbide slag and desulfurization ash on the basic properties and microscopic characteristics of fluid solidified soil, Ca(OH)₂ and CaSO₄ analytical reagents were replaced solely or simultaneously with the same amount of calcium carbide slag and desulfurization ash, and their effects on the flow value, bleeding rate and compressive strength of fluid solidified soil were tested. XRD and SEM were used to compare and analyze the phase composition and microscopic morphology of the samples prepared with two analytical reagents and two kinds of solid wastes at 28 d. The results show that the fluidities of the fluid solidified soil specimens prepared with calcium carbide slag and desulfurization ash are better than that of the fluid solidified soil mixed with Ca(OH)₂ and CaSO₄, and their bleeding rates meet requirement. The 28 d compressive strength of fluid solidified soil prepared with calcium carbide slag and desulfurization ash is less than that prepared with Ca(OH)₂ and CaSO₄ analytical reagents, but it can also meet the compressive strength requirements of most application scenarios.

Influence of Waste Circuit Board Non-Metallic Powder on Properties of Alkali-Activated Slag/Fly Ash Cementitious Material

LIU Yonghua, HU Xinlang, SHI Limin, GAO Yingli

2023, 42(12):  4456-4464. 

Asbtract ( 35 )   PDF (13220KB) ( 61 )  

References | Related Articles | Metrics

A novel alkali-activated slag/fly ash cementitious material was prepared by incorporating 0%~25% (mass fraction) waste circuit board non-metallic powder (NMP). The properties of this new material were evaluated, including its mechanical strength, hydration heat release, phase composition, and pore size distribution. The microstructural features were also analyzed. The results indicate that the addition of NMP not only reduces the workability and cumulative heat release of cementitious material, but also slightly reduces its 7 and 28 d compressive strength. When the NMP content is less than 15% (mass fraction), the 28 d flexural strength of cementitious material is positively correlated with the NMP content due to the presence of glass fibers, resulting in a maximum increase of 55.5%. Incorporating NMP reduces the proportion of pores with diameter between 100 nm and 1 000 nm, while improving the proportion of micropores with diameter below 100 nm, leading to an overall increase in total porosity. The resin particles in NMP are tightly bound to the cementitious material matrix, filling the voids between the fibers and the matrix. The addition of NMP does not affect the types of hydration products in the original cementitious material.

Ceramics

Research Progress of Ceramic Fiber Insulation Tiles and Its High Emissivity Coating

LAN Zhidan, REN Weimin, AN Nan, PENG Zhe, LI Song

2023, 42(12):  4465-4474. 

Asbtract ( 135 )   PDF (8623KB) ( 223 )  

References | Related Articles | Metrics

Ceramic fiber insulation tiles have the characteristics of low density, high temperature resistance, low thermal conductivity and excellent wave transmission performance. It is suitable to be used as thermal protection material in medium low temperature area of space vehicle. The application of high emissivity coating on the surface of ceramic fiber insulation tiles can effectively solve the problems of easy moisture absorption, low strength and easy performance degradation in the service process of ceramic fiber insulation tile. At the same time, it can block the high temperature erosion airflow and improve the energy reflectivity and thermal shock resistance. This paper mainly introduces the preparation methods of ceramic fiber insulation tiles and the influencing factors of their properties, summarizes the research progress of ceramic fiber insulation tiles and their high emission coatings in aerospace field, and looks forward to their future development.

Influence of Sodium Silicate Modulus on Rheology of Kaolin Slurry

LI Gang, BAO Zhilei, ZHANG Junjian, YU Huan

2023, 42(12):  4475-4481. 

Asbtract ( 39 )   PDF (4101KB) ( 51 )  

References | Related Articles | Metrics

In this study, sodium silicate with varying modulus was synthesized. The influence of sodium silicate modulus on the rheology of kaolin slurry was investigated. Based on the rheological analysis, it has been determined that the kaolin slurry exhibits the lowest shear viscosity when the sodium silicate modulus is 2.5 and the addition amount is 0.33% (mass fraction). Four different models are used to fit the flow curves, and it is found that the Herschel-Bulkley model could obtain the greatest correlation. In addition, the fitting degree is primarily influenced by the shear stress in the low shear rate region, which is mainly affected by the thixotropy of slurry. Then, the thixotropy of slurry with different sodium silicate modulus is characterized by shear hysteresis ring area, which verifies the view above. Finally, the molecular structure of sodium silicate with different modulus was analyzed using infrared spectroscopy. The results indicate the presence of a weak vibration at 589.5 cm^-1 in the vibrational spectrum of sodium silicate with a modulus of 2.5, suggesting the presence of distorted 6-membered rings. The annular silicates interact with kaolin particles through Coulombic force, leading to the formation of large aggregates. This interaction prevents the connection between the edges and faces, disrupts the thixotropic structure, and consequently reduces viscosity. This study is helpful to understand the deep reason of the influence of sodium silicate modulus on the mechanism of deflocculation, and provide scientific basis for optimizing the formulation and processing of ceramic slurry.

Sintering Process of Granite Scrap Mud Building Ceramics

GENG Zhenhua, LI Kai, BI Zhiying, LIU Wenhua, LI Haijian, SUN Gaomeilin, WU Ping

2023, 42(12):  4482-4489. 

Asbtract ( 39 )   PDF (7850KB) ( 59 )  

References | Related Articles | Metrics

In order to promote the comprehensive utilization of bulk solid waste and reduce the environmental pollution caused by granite scrap mud, this paper explores a method of preparing ceramic bodies by high temperature sintering using granite scrap mud, high alumina clay and a small amount of additives. The effects of raw material ratio and additive content on the mechanical properties and microstructure of sintered ceramic tiles were studied. The results show that the plasticity of the granulation powder can be improved by adding polyvinyl alcohol (PVA) solution to the ball milling raw material, and the proportion of the granite scrap mud in the body greatly increases. High alumina clay can improve the sintering characteristics of granite scrap mud and the comprehensive mechanical properties of finished products. Among them, the sintering temperature of the finished product with granite scrap mud content of 80% (mass fraction) and clay content of 20% (mass fraction) is about (1 160±30) ℃, the bulk density of the finished product is 2.43 g/cm³, the water absorption rate is 1%, the bending strength is 54 MPa, and the compressive strength is 341 MPa. The comprehensive utilization rate of granite scrap mud is high, and the comprehensive cost is low, which provides an efficient and feasible scheme for the comprehensive utilization of saw mud.

Glass

Preparation and Properties of MgO-Al₂O₃-SiO₂ Glass-Ceramics with Different Al₂O₃/SiO₂ Ratios

ZHAN Lingli, JIA Han, ZHANG Xiaofeng, LI Hong, XIE Jun, XIONG Dehua

2023, 42(12):  4490-4500. 

Asbtract ( 118 )   PDF (9274KB) ( 151 )  

References | Related Articles | Metrics

MgO-Al₂O₃-SiO₂ (MAS) glass-ceramics were prepared by sintering method. The effects of different Al₂O₃/SiO₂ mass ratios on the microstructure and physicochemical properties of MAS glass-ceramics were studied. The structure and surface morphology of parent glass and glass-ceramics were characterized by XRD, DSC, FTIR and FESEM. The density, mechanical properties, corrosion resistance, thermal properties and dielectric properties of glass-ceramics were tested. The results show that as the mass ratio of Al₂O₃/SiO₂ increases from 0.52 to 0.64, the glass transition temperature T_g of the parent glass increases and the crystallization peak temperature T_p of the parent glass decreases, promoting the precipitation of α-cordierite crystal phase. The density of the samples fluctuates in the range of 2.52~2.60 g/cm³, dielectric constant ε_r increases from 1.73 to 4.51, thermal expansion coefficient decreases from 4.46×10^-6 to 2.38×10^-6 ℃^-1, dielectric loss tan δ fluctuates in the range of 8.4×10^-3~3.7×10^-3, and the flexural strength fluctuates in the range of 80~120 MPa.

Preparation and Performance of Antibacterial Ultra-Clear Glass

TIAN Yingliang, WEI Xipeng, ZHANG Qingshan, HAN Yanli, HE Feng, ZHAO Zhiyong, LI Bo, YAN Jianhua, HE Youle, WANG Changjun

2023, 42(12):  4501-4508. 

Asbtract ( 47 )   PDF (3765KB) ( 80 )  

References | Related Articles | Metrics

In this paper, a kind of ultra-clear glass with high antibacterial properties was prepared with high temperature melting method by introducing AgNO₃ as the effective antibacterial component. The glass has good visible light transmittance, colorimetric value and antibacterial properties, in which the visible light transmittance of the glass at 380~780 nm is about 91.5%. With the increase of AgNO₃ content, the brightness of glass gradually decreases and the yellow phase increases, but the degree of yellowing is small. The antibacterial rate of glass against Escherichia coli and Staphylococcus aureus is more than 90%. The phase analysis and valence state analysis of Ag were carried out by XRD and XPS, and the dissolution of Ag⁺ in glass samples was analyzed by ICP-OES. XRD and XPS test results show that the glass is amorphous, and the doped Ag element exists in the form of Ag⁺ rather than Ag elemental. In addition, the amount of Ag⁺ dissolved in the glass increases with the increase of time, but the dissolution rate of Ag⁺ decreases. The amount of Ag⁺ dissolved in the glass samples of each group is consistent with the result of antibacterial detection within 24 h, which confirms the antibacterial property of the AgNO₃ in glass.

Experimental Investigation of Thermochemical Regeneration Technology for Oxy-Fuel Combustion Glass Furnace

ZENG Hongjie, ZHOU Wencai, GUAN Min, SHEN Zhongjie, CHEN Shuyong, LI Hongqiang, QI Shuai, ZUO Zefang

2023, 42(12):  4509-4517. 

Asbtract ( 46 )   PDF (6757KB) ( 64 )  

References | Related Articles | Metrics

Compared with traditional oxy-fuel combustion technology and air combustion technology, the thermochemical regeneration technology of glass furnace has remarkable energy saving effect and is a cutting-edge and disruptive technology for green and low-carbon development of the future high energy consuming glass industry. The thermochemical regeneration technology of glass furnace was experimentally studied by using atmospheric tube furnace and the effects of different experimental conditions on the thermochemical reforming reaction performance of methane/flue gas were analyzed. The results show that methane/flue gas can spontaneously undergo thermochemical reforming at high temperature without catalyst. When the reforming reaction temperature is lower than 900 ℃, the thermochemical reforming reaction of methane/flue gas does not occur. A reaction temperature of 1 200 ℃ and a reaction time of more than 10 s can ensure the full progress of the reforming reaction. The increase of methane and CO₂ content in the reforming reaction gas is conducive to the increase of hydrogen and carbon monoxide yields in the synthesis gas, respectively.

Refractory Materials

Effect of Gahnite on Properties of High Alumina Castable

HAN Jun, LIU Rui, LYU Lihua

2023, 42(12):  4518-4523. 

Asbtract ( 53 )   PDF (8718KB) ( 79 )  

References | Related Articles | Metrics

In this paper, gahnite (ZnAl₂O₄) was prepared with solid phase reaction by ZnO and Al₂O₃ as raw materials. The micro-structure change of ZnAl₂O₄ was researched when ZnO/Al₂O₃ molar ratios were 1.0:0.9, 1.0:1.0 and 1.0:1.1, respectively. In addition, the effect of ZnAl₂O₄ on properties of high alumina castables were studied. The results show that when the molar ratio of ZnO to Al₂O₃ is 1.0:0.9, due to the excessive ZnO, it volatilizes because of the removal of O^2- to produce liquid phase, and the surface of ZnAl₂O₄ particles is microporous structure. When the molar ratio of ZnO and Al₂O₃ is 1.0:1.0 (standard molar ratio), the surface of ZnAl₂O₄ particles with standard molar ratio is smooth. The lattice strain value (0.085 86) of standard molar ratio ZnAl₂O₄ is the smallest, which can capture more manganese ions and iron ions in steel slag. When the molar ratio of ZnO to Al₂O₃ is 1.0:1.1, the surface of ZnAl₂O₄ particles is rough. The high alumina castable with standard molar ratio ZnAl₂O₄ has denser structure, highest strength and best slag resistance.

New Functional Materials

Effects of C-Coated Cu Nanoparticles on Properties of Na₂SO₄·10H₂O Phase Change Nanofluids

LIU Xin, CHEN Fenglan, YU Pengcheng, WANG Chang’an, TIE Shengnian

2023, 42(12):  4524-4531. 

Asbtract ( 38 )   PDF (8971KB) ( 53 )  

References | Related Articles | Metrics

The effects of C-coated Cu nanoparticles on the rheological behavior of mirabilite phase change nanofluids with different mass fraction (1.0%, 1.5%, 2.0%, 3.5%, and 5.0%) at different temperatures were investigated. The viscosity of C-coated Cu nanoparticles phase change nanofluids was investigated at different shear rates (39.91~140 s^-1) and different temperatures (35~50 ℃). The results show that the hydrothermal method successfully prepares C-coated Cu nanoparticles. Nanofluid samples with mass fraction of 1.0% C-coated Cu nanoparticles at 35 ℃ and 1.5% C-coated Cu nanoparticles at 35, 40 ℃ exhibit Newtonian fluid behavior, but nanofluid samples exhibit non-Newtonian fluid behavior at other temperatures. When the mass fraction of C-coated Cu nanoparticles increases to 2.0%, 3.5% and 5.0%, the samples exhibit non-Newtonian fluid behavior, which conforms to the power law model. At the same time, the thermal properties of mirabilite composite phase change energy storage materials were studied. The composite phase change nanofluid has higher thermal conductivity, lower undercooling, and better cycle stability.

Effect of ZrO₂ Particle Size on Microstructure of Nano ZrC Synthesized by Salt Assisted Combustion

ZHAN Faqi, XU Shipeng, ZHANG Hua, LIU Xiao, ZHU Min, ZHENG Yuehong, LA Peiqing

2023, 42(12):  4532-4541. 

Asbtract ( 36 )   PDF (9425KB) ( 52 )  

References | Related Articles | Metrics

Nano ZrC powder was prepared by salt assisted combustion synthesis process. The effect of raw material ZrO₂ particle size on the microstructure of nano ZrC powder and its mechanism were studied. The results show that in ZrO₂-Mg-C system, with the decrease of ZrO₂ original particle size (200→10 nm), the reaction activity of carbon zirconium system increases and the free carbon content in ZrC decreases gradually. The average particle size of ZrC powder decreases with the decrease of ZrO₂ particle size. When ZrO₂ with particle size of 10 nm is added, the average particle size of ZrC powder is 48 nm, and the spherical like morphology tends to be more uniform. The particle size of raw material ZrO₂ decreases and the specific surface area increases, which improve the reaction activity and carburizing speed, so as to reduce the influences of reaction time and reaction temperature on crystal growth, and obtain high-purity nano ZrC powder with uniform distribution.

Microwave Absorbing Properties of Mesoporous Heterogeneous SiO₂@SiC@C Microsphere Prepared by Magnesiothermic Reaction

GAO Bowen, ZHANG Xiaowei, LIU Yuan, LI Qiwang, CHEN Liuling, ZHANG Weike

2023, 42(12):  4542-4551. 

Asbtract ( 46 )   PDF (11911KB) ( 52 )  

References | Related Articles | Metrics

The mesoporous SiO₂ synthesized by modified Stöber method was used as precursor. The phenolic resin was coated on the surface of SiO₂ by self-assembly technology and SiO₂@C was formed after carbonization. The mesoporous heterogeneous SiO₂@SiC@C microspheres with uniform morphology were obtained by magnesiothermic reaction at 800 ℃. As shown in the characterization results of XRD, XPS, Raman, BET, SEM and TEM, the SiO₂@SiC@C microspheres were composed of SiC, amorphous SiO₂, amorphous C and SiO_xC_y phases, and a large number of mesoporous structures can be found on the surface. The mesoporous heterogeneous SiO₂@SiC@C microspheres exhibit excellent microwave absorption performance in the simulation results of microwave absorption performance. When the simulated matching thickness is 2 mm, the minimum reflection loss reaches-36.83 dB at 17.74 GHz. The maximum absorption bandwidth reaches 6.63 GHz at the simulated matching thickness of 2.5 mm, completely covering the Ku band. The mesoporous heterogeneous SiO₂@SiC@C microspheres show strong absorption and wide frequency band. This is the result of the synergistic effect of mesoporous structure optimizing the impedance matching and heterogeneous interface enhancing the interface polarization. The mesoporous heterogeneous SiO₂@SiC@C microspheres prepared in this experiment can meet the application requirements in the field of electromagnetic wave absorption protection.

Synthesis and Regeneration of ZSM-5 Zeolite and Its Adsorption on Organic Matter in Wastewater

YANG Luting, LIU Yong

2023, 42(12):  4552-4558. 

Asbtract ( 57 )   PDF (9217KB) ( 70 )  

References | Related Articles | Metrics

For the removal of organic matter in high salinity wastewater, ZSM-5 zeolites with different silicon aluminum molar ratios(Si/Al) were synthesized by hydrothermal method, and were analyzed using XRD, SEM, XRF and BET. The removal effects of zeolites with different silicon aluminum ratios on organic matters in high salinity wastewater were investigated. The temperature of the regeneration of zeolites through calcination were studied also, and the reuse performance of zeolites in the adsorption process of organic matter in high salinity wastewater was evaluated. The results show that with the increase of silicon aluminum ratio of raw material, the particle size of ZSM-5 zeolite gradually decreases, the specific surface area gradually increases, and the adsorption efficiency of zeolite for organic matter in wastewater gradually increases. When silicon aluminum ratio of raw material Si/Al is 500, the synthesized ZSM-5 zeolite has a better adsorption effect on organic matter in wastewater. During 15 times of regeneration and reuse, the removal rate of total organic carbon (TOC) in wastewater is greater than 92.5%. The optimal calcination regeneration temperature of ZSM-5 zeolite is 650 ℃.

Road Materials

Properties of Geopolymer Grouting Material Considering Road Interlayer Hollowing Diseases

ZHAO Honghao, LIU Xianming, LI Peng, ZHANG Wenliang, WANG Kai, DONG Kun, WANG Junjie, XU Yi

2023, 42(12):  4559-4571. 

Asbtract ( 50 )   PDF (6470KB) ( 62 )  

References | Related Articles | Metrics

The shape of road interlayer hollowing diseases is relatively flat, and the consolidated body after grouting repair is prone to bending. Therefore, it is necessary to focus on improving the toughness and bending resistance of the grouting material. Currently, there is a lack of grouting repair material which target its disease characteristics. Therefore, slag and fly ash were used as the main raw materials, vinyl acetate-ethylene copolymer redispersible powder (VAE glue powder) was added to improve the brittleness and flexural strength of geopolymer grouting material, and conduct geopolymerization reaction under the excitation of water glass which modulus adjusted by NaOH. A new type of geopolymer grouting material was developed, and the influences of factors such as VAE glue powder content on the performance of geopolymer grouting material was explored. The experimental results show that the optimal mix ratio for the comprehensive performance of the new geopolymer grouting material is 40% slag powder, 60% fly ash, 2% VAE glue powder, 0.1% air entraining agent, 2% UEA expansive agent, 25% water glass, 1.6 water glass modulus and 0.35 water-cement ratio. The newly developed geopolymer grouting material increases to 10.8% in flexural strength and decreases to 17.4% in brittleness, making it suitable forroad interlayer hollowing diseases. The research conclusion has a certain promoting effect on promoting the development of road hidden disease repair technology and ensuring the long-term safety and stability of road operation.