Table of Content

15 January 2021, Volume 40 Issue 1

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Cement and Concrete

Review of Rapid Test Methods for Chloride Diffusion Coefficient

SHI Yueyi, GUO Zengwei, GUO Ruiqi

2021, 40(1):  1-12. 

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Chloride diffusion coefficient is an important parameter to evaluate the anti-permeability of chloride ion and residual life of concrete structures,hence it is essential to choose a fast and accurate test method to acquire chloride diffusion coefficient.Chloride migration coefficient from non-steady-state migration experiments (Rapid Chloride Migration,RCM) was taken as a benchmark method,and contrasted with the other common test methods at home and abroad.The characteristics and application scope of these methods,as well as their conversion relations with RCM method were concluded.The results show that compared with the RCM method proposed by current specifications,Permit (Permeation Migration) method is mainly used in onsite non-destructive testing,NEL and ACMT (Accelerated Chloride Migration Test) methods are usually used to measurechloride diffusion coefficient in steady-state migration.ACMT method is more suitable used for residual life prediction,while NEL method is preferred for quality acceptance and durability design.Some scholars have established some conversion relationships between RCM method and the other test methods through experiments,but it is only applicable to the concrete in those studies,and whether it is applicable to other concrete needs further study.

Mechanism of Chloride Binding and Its Influence Factors inCement-Based Materials

SHI Tianyao, CHEN Xingyu, ZHANG Min, LIU Qian

2021, 40(1):  13-24. 

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Chloride ion erosion is the main cause of steel corrosion in cement-based materials.When chloride binding in cement,the corrosion of steel bars can be effectively delayed.This article summarizes from three aspects:(1) chloride binding mechanism;(2) test methods and characterization of chloride binding;(3) the influencing factors of chloride binding.Specific research are the cement components and hydration products how to binding chloride ion,as well as applicability of different test methods.Some factors that influenced chloride binding are analyzed,such as supplementary cement materials,curing time and pH etc.A further study is proposed in order to provide reference for the future study of reinforced concrete life prediction.

Research Status of Electrochemical Chloride Extraction Technology ofReinforced Concrete

LI Shupeng, JIN Zuquan, XIONG Chuansheng

2021, 40(1):  25-33. 

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The electrochemical chloride extraction (ECE) technology evacuates chloride ions by applying a constant voltage between the external anode and the cathode of reinforcing bars,which aims to recover the passivation of the reinforcements and also protecting the reinforced concrete.To have a better understanding of ECE technology,this paper has summarized the advanced achievements on the topic of ECE by researchers worldwide,meanwhile,the impact factors are also investigated.Moreover,the effects of ECE technology on the bonding strength,macroscopic performance and microstructure of reinforced concrete are comprehensively introduced.Finally,the remaining drawbacks of ECE technology are put forward and the prospect of future researches is also proposed.It is expected that electrochemical dechlorination technology will play a better role in improving the durability of coastal concrete structures.

Mechanical Properties and Crack Development Characteristics ofCement-Solidified Mud Soil under Dry-Wet-Freeze-Thaw Cycles

TAO Pan

2021, 40(1):  34-40. 

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In order to study the effect of dry-wet-freeze-thaw (short as D-W-F-T) cycle on the properties of cement-solidified mud soil,triaxial shear tests,CT scan tests and SEM scan tests were carried out under different times of D-W-F-T cycle,and the mechanical characteristics and microstructure damage rules of cement-solidified mud soil were studied.The results show that the stress-strain curves of cement-solidified mud soil shows the strain hardening type.The internal friction angle and cohesion index gradually decrease with the increase of the number of D-W-F-T cycles,and the trend of exponential and linear decay are presented,respectively.The cracking evolution rules of the samples are quantitatively analyzed based on the binary CT scan images.It is found that the crack content of the sample increases exponentially with the increase of the number of D-W-F-T cycles.It is also observed by SEM scanning test that the D-W-F-T cycle causes the loss of cement-based materials in the samples and the decrease of compaction between particles,which is the microscopic mechanism that leads to the crack expansion and the mechanical properties weakening of cement-solidified mud soil.

Effect of Natural Zeolite Powder on Water Resistance ofMagnesium Oxychloride Cement

SUN Enyu, CHEN Xiaoyang

2021, 40(1):  41-47. 

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Magnesium oxychloride cement (MOC) has the advantages of light weight,high strength and high wear resistance,however,its poor water resistance restricts its development in the construction industry.To prepare high water resistance of MOC,natural zeolite powder (NZOP) was used as admixture.The effect of NZOP on the setting time,compressive strength and water resistance of MOC was investigated.Meanwhile,X-ray diffractometer,scanning electron microscope and mercury intrusion porosimetry were used to analyze the change of phase composition,microstructure and pore structure of modified MOC.In addition,the concentration of Cl^- in immersing solution was measured by ion chromatograph.The results show that NZOP effectively improves the compressive strength and water resistance of MOC and reduces the initial and final setting time of MOC.After adding 30% (mass fraction) NZOP and 0.5% (mass fraction) phosphoric acid,the 28 d compressive strength and 28 d softening coefficient of MOC reach up to 75.8 MPa and 0.91,respectively,and the concentration of Cl^- in immersing solution is as low as 9.0 mmol/L.In addition,the concentration of Cl^- in immersing solution increases with the decrease of the softening coefficient of MOC.

Performance of Magnesium Potassium Phosphate Cement-BasedAnticorrosive Coating with High Fluidity under Long-TermSoaking in Different Solutions

HAN Chao, YANG Jianming, SHAN Chunming, WU Qing, HE Fuqiang

2021, 40(1):  48-54. 

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In order to explore the performance ofmagnesium potassium phosphate cement (MKPC)-based anticorrosive coating with high fluidity in different solution environments,the strength,dry shrinkage and water absorption of MKPC-based anticorrosive coating were tested by immersion in fresh water,5% sodium sulfate solution and 3.5% sodium chloride solution (both are mass fraction).In addition,the corrosion mechanism of MKPC-based anticorrosive coating under long-term soaking was analyzed by SEM-EDS and XRD.The results show that the high fluidity MKPC has good corrosion resistance in fresh water environment,and better corrosion resistance in 3.5% sodium chloride solution and 5% sodium sulfate solution.

Modeling Method of Cement Clinker Accumulation Body Based onDynamic Neural Network

WEN Yan, HUANG Bolin, YUAN Lin, LIU Haoran, JU Yanxu

2021, 40(1):  55-63. 

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The particle packing is an important issue in engineering.In order to construct the discrete element numerical model of the particle accumulation body,an experiment for collecting its structural parameters such as diameter and coordinate was designed firstly.With the cement clinker packing of the grate cooler in the background,cement clinker was used to form the accumulation body.And a series of images were collected by cutting the particle accumulation body into slices.Then a battery of treatments was carried out to obtain its structural parameters.At the same time,a prediction model was trained based on neural network in order to rebuild accumulation body model and its statistical accuracy was verified.The good precision of the model indicates that it meets the modeling requirements to a certain extent.

Experimental Study on a Chlorine Free Composite Cement Grinding Aid

CAO Hu, LI Haiyan, CHEN Menglong, DUAN Benhou, GAO Deng, WANG Gan, SONG Liuping, AI Chunhun

2021, 40(1):  64-70. 

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A chlorine free composite cement grinding aid was studied.The grinding aid does not contain halogen ions which corrode the equipment.It can effectively improve the grinding efficiency of cement,improve the distribution of cement particles and enhance the strength of cement.The new modified alcohol amine was selected as the matrix material of grinding aids,and three kinds of common raw materials with auxiliary materials were used to make small grinding test.The performance of grinding aids was evaluated,and the influence of each component was analyzed.The optimal ratio of each material was determined by range analysis,and the hydration products of cement were characterized by SEM.Compared with the blank sample,the performance of cement is significantly improved by the grinding aid,in which the cement 45 μm sieve residue decreases by 24.0%,3 d compressive strength increases by 3.8 MPa,and 28 d compressive strength increases by 5.4 MPa.And the cement using the grinding aid has better working performance,higher strength and better durability in concrete application.

Effect of Polymer Powder Content on Rheological Properties ofCement Paste Modified by Cellulose Ether

LUO Wenjin, WANG Liying

2021, 40(1):  71-76. 

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The effect of polymer powder (PP) content on the rheological properties and thixotropy of cellulose ether (HPMC) modified cement paste was studied by Anton Paar MCR 302 rheometer.The results show that HPMC modified cement paste with PP behaves as a shear-thinning fluid.When the shear rate is small,the viscosity of cement paste decreases significantly.The higher the content of PP is,the larger the yield stress and viscosity coefficient fitted by Herschel-Bulkey model.Moreover,PP can increase the area of thixotropic hysteresis loop and the structural recovery rate of three-stage thixotropy test.There is a positive linear relationship between yield stress and thixotropic loop area of cement paste incorporating PP and HPMC.

Experimental Study on Mortar Materials with Fissures Filled withHigh Permeability Modified Epoxy Resin

ZHU Haowei, LIU Changwu, CHEN Xiaoqiang, ZHAO Chao

2021, 40(1):  77-82. 

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Cylindrical mortar specimens containing pre-made fissures were prepared,and fissures were of four kinds of different inclination angles (0°,30°,45° and 60°,respectively).Fissures of specimens were filled with high permeability modified epoxy resin under the effect of gravity and without grouting pressure.Uniaxial compression tests were carried out before and after the process of grouting,correspondingly.Test results show that the high permeability modified epoxy resin permeates into fissures of specimens relying on its own permeability.After solidification,it improves the uniaxial compressive strength (UCS) of specimens with different inclination angles of fissures to various extents.Among them,the improvement of UCS is the most significant when fissures inclination angles are 45° and 60°,respectively.The UCS of specimens decreases gradually with the increase of the inclination angle from 0° to 60°,no matter whether fissures are filled with epoxy resin or not.Failure modes of specimens before and after filling epoxy resin see no much difference,most of which are tensile splitting failures caused by tensile stress.The research results provide some data support and theoretical basis for analyzing the influence of epoxy resin on rock mass strength in practical engineering.

Study on Corrosion Resistance of Nano SiO₂-CSA-OPCRepair Mortar in Saline Soil

ZHU Dianzhi, LIU Zuoyu, DONG Changhong, LIU Qingfeng, NIU Mengdie, LI Guoxin

2021, 40(1):  83-89. 

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In order to study the corrosion resistance of nano-SiO₂-sulphoaluminate cement-ordinary Portland cement (NS-CSA-OPC) repair mortar in saline soil,the long-term semi-immersion test in NaCl solution,Na₂SO₄ solution and NaCl-Na₂SO₄ composite solution was used to simulate the saline soil corrosion environment and accelerate the corrosion of NS-CSA-OPC mortar specimens.The change law of NS-CSA-OPC repair mortar on the mass,relative dynamic elastic modulus,compressive corrosion resistance coefficient and chloride ion content under three corrosion environments were tested.The results show that NS-CSA-OPC mortar shows excellent corrosion resistance in the three kinds of corrosion solutions,and the compressive corrosion resistance coefficients of the system are higher than 1.0 after soaking for 270 d;in the long-term semi-immersion test,the corrosion degree of three corrosion solutions to NS-CSA-OPC repair mortar is:Na₂SO₄>NaCl-Na₂SO₄>NaCl;the existence of chloride mitigates the corrosion expansion damage of sulfate.

An Improved Support Vector Regression Method forConcrete Strength Prediction

CAO Fei, ZHOU Yu, WANG Chunxiao, REN Mengyu, ZHOU Feng

2021, 40(1):  90-97. 

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The compressive strength of concrete is an important indicator affecting construction quality.Predicting the concrete strength according to some key parameters serves as a reference for site construction.Based on support vector regression (SVR),a weighted SVR artificial intelligence algorithm about Mahalanobis distance (MWSVR) is proposed to predict concrete strength.Different from the traditional method,all training samples are treated uniformly,but the proposed algorithm assigns different importance to each training sample based on its distance from the test set.The training sample closer to the test set shows more importance,and thus the model assigns a higher penalty factor to obtain a better regression hyperplane.Compared with the methods of decision tree,random forest,BP neural network,RBF neural network,and conventional SVR,the proposed algorithm shows the lowest root-mean-square-error.

Freeze-Thaw Damage and Life Prediction Model ofNatural Pumice Concrete

WANG Xiaoxiao, LIU Chang, YIN Liqiang, YAN Changwang, LIU Shuguang

2021, 40(1):  98-105. 

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Inner Mongolia is rich in natural pumice,which can be used as coarse aggregate of lightweight aggregate concrete.In order to study the freeze-thaw damage law of natural pumice concrete (NPC),the freeze-thaw test was carried out on specimens with five kinds of mixing ratios.The relative dynamic elastic modulus and mass loss of NPC were obtained,and then the influence of pumice aggregate on the concrete frost resistance was analyzed.Based on the hydrostatic pressure theory and the fatigue damage theory,the material coefficient of NPC was deduced,the freeze-thaw damage model and life prediction model of NPC were established,and as an example,the life of NPC in Bayannur,Inner Mongolia in winter was calculated.The results show that pumice aggregate reduces the hydrostatic pressure of concrete and improves its frost resistance.The calculated value of relative dynamic modulus of the NPC is in great agreement with the test value.The life expectancy values of five groups of NPC reach 65 a,84 a,112 a,131 a and 50 a,meeting the safety operation life.

Design Method of Novel Recycled Pervious Concrete forResisting Rainstorm and Waterlogging

NIU Zhigang, ZHU Pinghua, CHEN Chunhong, WANG Xinjie, LIU Hui

2021, 40(1):  106-112. 

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Paving pervious concrete pavement is an effective way to reduce the urban rainstorm waterlogging disaster.To realize the rational application of pervious concrete pavement under different rainstorm grades,improve the utilization rate of renewable resources,and achieve the purpose of resisting rainstorm and waterlogging,a novel design method of recycled pervious concrete was proposed.The quantitative relationships between porosities and rainstorm grades were established,and the optimum porosity ranges of recycled pervious concrete which can resist different rainstorm grades were determined.Based on the relationship between porosity and strength,the strength grade of concrete was defined and then the mix proportions were designed.The mechanical strength and rainstorm simulation tests of the novel recycled pervious concrete were verified and analyzed.The results show that the compressive and flexural strength of recycled pervious concrete with different porosities meet the requirements of pervious concrete pavement.This concrete possesses excellent resisting rainstorm and waterlogging performance as well.The design method of the novel recycled pervious concrete for resisting rainstorm and waterlogging provides a reliable basis for the design of pervious concrete pavement in different regions (under different rainstorm grades).

Finite Element Analysis of Performance of Steel Plate Concrete CompositeShear Wall-Steel Beam Joint Based on Prefabricated Cross U-Shaped Connector

WAN Xin, GAO Lingyu, CHEN Ming, MING Wenhui

2021, 40(1):  113-122. 

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In order to study the mechanical properties of steel plate concrete composite shear wall-steel beam joint based on prefabricated cross U-shaped connector,numerical simulation of the joint model under uniaxial load and low cyclic loading was carried out using the refined general finite element software ABAQUS 6.14.The influences of U-shaped plate thickness,U-shaped plate length and steel beam span-to-height ratios on mechanical properties of the joint were discussed.The results show that the steel plate concrete composite shear wall-steel beam joint based on prefabricated cross U-shaped connector has good plastic deformation capacity and tensile bearing capacity.Each joint model has good hysteresis performance and energy dissipation capacity,and the equivalent viscous damping coefficient is between 0.302 9 and 0.400 1.The U-shaped plate length has no obvious influence on the initial stiffness and energy dissipation of the joint.The ductility and energy dissipation of the joint model perform well when the thickness of the U-shaped plate is about 12 mm.With the increase of span-to-height ratios of steel beam,the rotational stiffness and ductility as well as the energy dissipation capacity of the joint are significantly improved.

Solid Waste and Eco-materials

Research Progress on Synthesis and Application of ZeoliteBased on Coal Fly Ash

SUN Yanwen, WANG Lianyong, YANG Xianglan, CUI Jiaxin, XUE Haiyue, HAN Jianli

2021, 40(1):  123-132. 

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Coal fly ash is a solid waste produced by coal-fired power plants.Its main components contain a large proportion of SiO₂ and Al₂O₃,and it is an ideal raw material for the synthesis of zeolite.With the deepening of research,the synthesis method of zeolite by coal fly ash has been gradually mature.From the initial one-step hydrothermal method to the present composite hydrothermal method,from raw coal fly ash as raw material to the pre-treated coal fly ash as raw material,the synthesis process of zeolite by coal fly ash has been progressing.The research progress in pretreatment of coal fly ash,synthesis method of zeolite and application field of the product are reviewed.And the overall development of zeolite based on coal fly ash is expected.

Review on Applied Research of Recycled Expanded Polystyrene in Concrete

LUO Tiantian, LIU Weisen, GUO Yingjian, LI Chengye, MA Yuwei

2021, 40(1):  133-145. 

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The paper summarized the application of recycled expanded polystyrene (EPS) particles in concrete.Firstly,the differences between recycled EPS and original EPS were compared.The relationship between density grade and mechanical properties of recycled EPS concrete was elaborated.Other properties of EPS concrete,such as thermal performance,fire resistance performance,sound insulation and wave absorption,were introduced.Secondly,the influencing factors of recycled EPS concrete were elaborated from the aspects of EPS particle gradation and content,fiber,modifier,mineral admixture,water cement ratio.Finally,the industrial application of recycled EPS concrete was summarized,and the future research of recycled EPS concrete was prospected.The possible problems in the future research and application process were proposed.

Summary of Research on Self-Compacting Rubberized Concrete Performance

TIAN Lei, QIU Liuchao, HU Xiao

2021, 40(1):  146-162. 

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Self-compacting rubberized concrete is a new type of building material made by processing waste tires into rubber particles and adding them to self-compacting concrete.Compared with conventional concrete,it has the obvious advantages of low brittleness,excellent deformability,energy saving and pro-environment after hardening.To understand the latest research status about self-compacting rubberized concrete,the research on self-compacting rubberized concrete worldwide in the past ten years was comprehensively introduced from the aspects of self-compacting ability (flow ability,viscosity,passing ability,segregation resistance),mechanical properties (compressive strength,splitting tensile strength,elastic modulus,flexural strength,impact resistance,fatigue behaviour,damping ratio),durability (drying shrinkage,water absorption,freeze-thaw resistance,chloride ion penetration,electrical resistivity) and internal microstructure.Finally,the conclusions were summarized,and some suggestions were proposed for the future research and promotion of self-compacting rubberized concrete.

Experimental Study on Basic Characteristics and PozzolanicActivity of Natural Aeolian Sand

ZHENG Mulian, JING Haiyang, CHEN Wang, ZHU Linlin, ZHANG Shu, GAO Yuan

2021, 40(1):  163-171. 

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Northwest China is rich in aeolian sand resources.If aeolian sand can be used actual projects locally,huge economic and social benefits will be produced.Although there have been many researches on the application of aeolian sand engineering at home and abroad,there is still a lack of systematic research and analysis on the basic physicochemical properties and pozzolanic activity of natural aeolian sand,most of which are confined to a specific engineering application.In this paper,the aeolian sands in the three desert regions of Taklamakan,Gurbantunggut and Tengger were sampled.The physical characteristics of natural aeolian sand,such as particle composition,apparent density,bulk density,porosity,mud content,moisture content,water absorption,micro-morphology,and chemical characteristics such as pH,chemical composition,mineral composition and alkali activity were tested and analyzed.The results show that there are some similarities in physical and chemical characteristics of aeolian sand in the three regions.In addition,the pozzolanic activity of natural aeolian sand was evaluated by activity index method,and six chemical activators were used to improve its activity.The study proves that the pozzolanic activity of natural aeolian sand is low,and the addition of Na₂SO₄ and Ca(OH)₂ improves the pozzolanic activity of natural aeolian sand.

Adsorption Properties of Inorganic and Organic Modified Sepiolite to Benzene

FANG Jiajun, REN Zijie, GAO Huimin, ZHOU Xianwu, ZHOU Peng

2021, 40(1):  172-179. 

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Indoor benzene pollution is mainly caused by decoration and decoration materials.As a first-level carcinogen,prolonged exposure to benzene will cause many chronic diseases.How to reduce indoor benzene pollution has attracted more and more attention.Many studies have proved that sepiolite can be used for soil pollution treatment,water pollution treatment and air pollution treatment.So the purified sepiolite was modified by hydrothermal modification,acid modification and hydrothermal acid leaching methods combine inorganic modification and organic modification of trimethoxyphenylsilane (PTMOS).The performance and mechanism of modified sepiolite adsorbing benzene gas were studied.The results show that the best condition for hydrothermal acid leaching methods combined inorganic modification is 0.6 MPa hydrothermal pressure treatment for 8 h,then treated by hydrochloric acid with a volume fraction of 10% for 8 h.The removal rate of sepiolite to benzene is 72.36% higher than that of rude ore.The best treatment condition for surface organic modification is 0.3 mmol·g^-1 of PTMOS,and the modification time of 6 h.The removal rate of sepiolite to benzene is 159.03% higher than that of rude ore.The surface organic modification has better adsorption effect than the sepiolite obtained by hydrothermal acid leaching combined modification.The adsorption of benzene by PTMOS-SP is suitable for Langmuir isotherm model,quasi-second-order kinetic model and intraparticle diffusion model.The adsorption process of benzene on the surface of PTMOS-SP consists of three stages:the outer surface diffusion stage,the pore diffusion stage,and the adsorption equilibrium stage.

Influence of Modified Diatomite on Cement-Based Humidity ControlMaterials Performance

FENG Lei, LOU Dai, RAN Ze, WEN Xiaodong, WANG Wei

2021, 40(1):  180-186. 

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The natural diatomite was modified by calcination and acid pickling,and then was used to replace some cementitious materials for preparing cement-based humidity control materials.The workability,mechanical properties,moisture absorption and desorption rates of cement-based humidity control materials mixed with natural diatomite was tested and compared with those of the modified diatomite.Based on that,the function mechanism of modified diatomite was investigated comprehensively through characteristics analysis of chemical composition and surface structure of diatomite before and after modification,and characteristic parameters of cement hardened body pore structure.The results show that mechanical properties and humidity-controlling performance of cement-based humidity control materials with modified diatomite are better than those of the natural diatomite with the same dosage.When the diatomite is calcined at 400 ℃ for 2 h and pickled with 50% (mass fraction) H₂SO₄ solution for 12 h,its specific surface area,average pore size and total pore volume increase significantly,and further enhances surface adsorption and capillary channel effect of water in the air.

Ratio Optimization of Slag-Based Solid Waste Cementitious MaterialBased on Response Surface Method

LIU Shulong, LI Gongcheng, LIU Guolei, WANG Fagang, WANG Jie, QI Zhaojun, YANG Jiguang

2021, 40(1):  187-193. 

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In order to promote the high-value application of iron and steel smelting waste slag,the cementitious material of solid waste was prepared from blast furnace slag,steel slag and desulfurized gypsum,and the ratio optimization of mine filling slurry was carried out.On the basis of exploring the physical and chemical properties of the test raw materials,with the aid of Box-Behnken in the Design-Expert software,17 sets of proportioning tests were designed.Taking steel slag,lime and desulfurized gypsum content as independent variables,and 28 d compressive strength of the backfill as the response value,a response surface polynomial regression model was constructed,and the influence mechanism of independent variable single factor and interaction on the strength performance of backfill based on variance analysis and response surface analysis was studied.The results show that the strength of backfill is highly sensitive to the response of a single factor,and has a strong significant effect on the interaction between factors.The order of significance of single factor is the content of lime,desulphurizing gypsum and steel slag.The interaction between steel slag and lime content is the decisive factor affecting the strength performance of backfill,followed by the interaction between lime and desulfurized gypsum content,and the interaction between steel slag and desulfurized gypsum is the least.The optimum parameters are steel slag content of 40%,lime content of 6%,desulfurization gypsum content of 12% and slag content of 42% (both are mass fraction).Under this parameter,the strength of backfill at 28 d is 4.03 MPa,and the relative error of parallel verification test is 2.83%,which confirmes the accuracy and scientificity of response surface method in optimizing the ratio of all-solid waste cementitious material.

Steam-Assisted Synthesis of Magadiite from Illite Silica Residue andIts Adsorption of Cu²⁺

GUAN Dongdong, LI Xinyu, CHEN Shuang, SU Chongyang, YANG Siqi, JIANG Nanzhe

2021, 40(1):  194-200. 

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The pure phase magadiite with high yield and high crystallinity was synthesized using illite silica residue by steam-assisted conversion (SAC).X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were used to investigate the influences of Na₂O/SiO₂ molar ratio,crystallization temperature (T) and crystallization time (t) on the structure and morphology of synthesized samples.The results show that the preliminary optimization of synthesis conditions of this system are n(Na₂O)/n(SiO₂)=0.15,T=170 ℃,t=16 h,and the sample morphology is rosette-like (about 12 μm).The Cu²⁺ adsorption test of magadiite synthesized was carried out,and the effects of adsorbent dosage,pH value,adsorption time and Cu²⁺ initial concentration on the adsorption effect were studied.The results show that when the adsorbent dosage is 2 g/L,the pH value is 5,and the adsorption time is 30 min,the maximum adsorption capacity of magadiite for Cu²⁺ is 25.99 mg/g.

Influence of Calcined Anhydrite Solubility on the Formation of Ettringite

QIAO Xiuchen, MA Dawei, XUE Yubing

2021, 40(1):  201-206. 

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In this research anhydrite calcined under the dry desulphurization temperature of circulating fluid bed (CFB) boiler was used to simulate dry desulphurization product.The formation of ettringite (AFt) was investigated by curing the mixture of calcined anhydrite and tricalcium aluminate (C₃A).It was discussed in this research that the feasibility of preparing building materials using CFB ash.The results show that the anhydrite calcined at 820 ℃ for 15 min is a plate-like crystal with sharp edges,and that calcined at 940 ℃ for 15 min is partly sintered.High temperature prepared anhydrite shows lower solubility.The formation of AFt reaches the top after 3 d curing.During the period,the anhydrite formed at 820 ℃ forms needle-shaped AFt by dissolving precipitation.While the anhydrite formed at 940 ℃ forms agglomerates by solid phase reaction.The carbonization reaction during long-term air curing will cause the decomposition of AFt.

Research on Water Stability of Steel Slag Asphalt Mixture

ZHANG Caili, WANG Chao, LI Song, DING Weizhe, TANG Xiuming

2021, 40(1):  207-214. 

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In order to study the volume stability and road performance characteristics of steel slag asphalt mixture at different water immersion time,rutting test,low temperature bending test,freeze-thaw splitting test,water immersion Marshall test,fatigue test and expansion test were carried out on hot stuffy steel slag asphalt mixture,cold abandoned steel slag asphalt mixture and limestone asphalt mixture respectively.The atomic force microscope was used to analyze the influence mechanism of water on the road performance of steel slag asphalt mixture.The results show that the high temperature stability,water stability,low temperature performance and fatigue performance of the steel slag asphalt mixture with qualified expansion are better than limestone asphalt mixture,in which the dynamic stability and residual stability of the steel slag asphalt mixture have growth.Using limestone fine aggregates instead of cold abandoned steel slag fine aggregates can improve the low temperature performance of cold abandoned steel slag asphalt mixtures.The crystalline material generated by the steel slag under the action of water immersion increases the surface area and surface roughness of the steel slag.The effect of water immersion improves the internal grinding resistance and cohesive force of the steel slag asphalt mixture,thereby improving the dynamic stability and residual stability.

Preparation and Properties Optimization of High StrengthCeramsite Obtained from Oily Sludge

YANG Xiaowei, ZHANG Aisheng, QU Junrong, YANG Ke, XU Jianhua, ZHU Ying

2021, 40(1):  215-222. 

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To solve the disposal problem of hazardous waste oily sludge,a high sludge doping sintered ceramsite which used oily sludge as raw material,loess,sand and clay as additives was prepared.The maximum content and the best conditions were tested by single factor experiment.The microstructure,phase composition and element distribution in the inner and outer layers of the ceramsite were investigated by scanning electron microscopy (SEM),X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS).Results show that when the sludge content is 60% (mass fraction),the sintering temperature is 1 140 ℃,and the sintering time is 20 min,the target ceramsite with low water absorption and high compressive strength is obtained.Based on GB/T 17431.1—2010 "Light weight aggregate and its test methods",the ceramsite 1 h water absorption is 0.32%,the bulk density is 1 020.3 kg/m³ and the barrel pressure strength is 40.992 MPa under the best conditions.

Ceramics

Research Progress of Si₃N₄ Ceramic for Dental Restoration Materials

JIANG Lei, FANG Xia, YIN Shuang, MAO Dongliang, PAN Limei, TANG Xuehua, YANG Jian

2021, 40(1):  223-230. 

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Silicon nitride has better mechanical properties,chemical stability and biocompatibility than dental ceramic restoration materials such as alumina and zirconia,and has been used in bio-orthopedic restoration.In recent years,some scholars have introduced silicon nitride ceramics into the field of dental restoration.Based on the introduction of the performance characteristics of silicon nitride ceramics,the research progress of silicon nitride ceramic dental implants,post-core crowns and veneering porcelain were reviewed.The future research direction of silicon nitride in the field of dental restoration was also expected.

Influence of Silicon Infiltration on Microstructure andProperty of Graphite

YANG Jinhua, AI Yingjun, CHEN Zimu, LIU Hu, QI Zhe, LYU Xiaoxu, JIAO Jian

2021, 40(1):  231-240. 

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Four kinds of graphite with different pore structure were selected for silicon infiltration (referred as infiltration) reaction.SEM,XRD,mercury intrusion porosimetry and CT methods were adopted to characterize the microstructure,phases and pore structure changes before and after the infiltration.The results show that the infiltrated samples are consisted of the graphite,silicon and silicon carbide,and the distribution of the silicon and silicon carbide is depended on the pore structure of the graphite.The porosities of all the infiltrated samples are lower than 1%,and the increase of the bulk density ranges from 21.08% to 35.94%.The strength of the infiltrated samples is 1.7 times to 6.2 times higher and the modulus is 2.7 times to 7 times higher than the graphite samples,and the increase of the strength is depended on the pore structure and crystal sizes of the graphite.Calculation results show that the infiltration process is controlled by the diffusion-reaction process.

Preparation and Properties of Gradient Porous Ag LoadedHydroxyapatite Ceramics

CHEN Chen, YU Jingyuan, LI Qiang

2021, 40(1):  241-251. 

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Gradient porous Ag loaded hydroxyapatite (Ag-HA) ceramic was prepared by adding pore-forming agent method.The effects of pore-forming agent distribution,sintering temperature on the porosity were studied.The phase composition and microstructure of the sintered products were analyzed,the compression and antibacterial properties of sintered gradient porous (Ag-HA) ceramics were measured.The experimental results show that the porosity of gradient porous Ag-HA ceramics increases with the increase of the contents of interlayer pore-forming agent,but the compressive strength decreases.With the increase of sintering temperature,the porosity of gradient porous Ag-HA ceramics decreases,but the compressive strength increases.When the distribution of pore-forming agent of is 20%-10%-20% (mass fraction),the pressing pressure is 100 MPa,the sintering temperature is 1 150 ℃ and Ag content is 2% (mole fraction),the porosity and compressive strength of the sintered gradient porous 2.0Ag-HA ceramics are 24.7% and 12.6 MPa,respectively.XRD analysis shows that the sintered products are HA phase doped with Ag ions.SEM observation shows that the pores of sintered samples present gradient distribution.The antibacterial experiments of gradient porous Ag-HA ceramics show that with the increase of Ag loading and porosity,the antibacterial ring diameter of gradient porous Ag-HA ceramics against escherichia coli and staphylococcus aureus increases.The gradient porous Ag-HA has good antibacterial properties,while pure HA ceramic shows no antibacterial properties.

Effect of Sintering Temperature on Microstructure and MechanicalProperties of Silicon Nitride Ceramic Balls

ZHANG Jing, WANG Wenxue, SUN Feng, LIU Lu, DONG Tingxia, ZHANG Baocun

2021, 40(1):  252-257. 

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Silicon nitride ceramic balls were prepared by gas pressure sintering process with α-Si₃N₄ powder as raw material and nano Y₂O₃ and Al₂O₃ as sintering aids.The effect of sintering temperature on microstructure and mechanical properties of ceramic balls was investigated.The results show that with the increase of sintering temperature,the Vickers hardness and crush strength of ceramic balls first increase and then decrease,and the fracture toughness increases continuously.The ceramic balls sintered at 1780 ℃ have the optinal comprehensive mechanical properties,the relative density of which is 99%,the Vickers hardness,fracture toughness and crush strength of which is 1 530 HV,7 MPa·m^1/2,and 296 MPa,respectively.

Glass

Cerium Doping Effect in Barium Strontium Titanate Glass-Ceramics

ZHAO Zhangyuan, LIANG Xuewei, ZHANG Yong

2021, 40(1):  258-265. 

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Cerium doping effect in (Ba,Sr)TiO₃ glass-ceramics has been investigated by X-ray photoelectron spectroscopy,ultraviolet-visible diffuse-reflectance spectroscopy,Fourier transform infrared spectroscopy and Raman spectroscopy.Studies were performed on specimens for BaO-SrO-TiO₂-Al₂O₃-SiO₂ glass system (with 0%,1%,2% and 3% mole fraction of cerium).With the change of relative content of Ce³⁺ and Ce⁴⁺,cerium mainly acts as Ce⁴⁺ in the Ti⁴⁺-site of (Ba,Sr)TiO₃ lattice at low content and then cerium substitution gradually occurs in the Ba²⁺/Sr²⁺-site as Ce³⁺ with increasing cerium mole content.The CeO₂ addition in the glass could effectively improve the connectivity of network structure.In (Ba,Sr)TiO₃ glass-ceramics,with the increase of cerium content (0% to 2%),the value of band gap energy decreases,electronic transition energy decreases,then electrons transit from the valence band to the conduction band easily,and the conductivity increases.In contrast,when the mole fraction of cerium increased from 2% to 3%,the value of band gap energy increases,so the conductivity decreases.The results of Raman spectra confirm that cerium ions diffuse into the (Ba,Sr)TiO₃ lattice structure and modify the tetragonality of the barium strontium titanate phase.

Effect of SnO on Structure and Performance ofSnF₂-P₂O₅-WO₃ Glass System

DIAO Jinlong, YU Tianlai, MO Dahong, ZHENG Tao, GUO Yanyan, LYU Jingwen

2021, 40(1):  266-270. 

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Sealing glass is widely used in vacuum microelectronics,aerospace,automobile and other industrial fields due to its good heat resistance,high chemical stability and mechanical strength.Phosphate glass has the characteristics of low cost,low characteristic temperature and low stability,which is often used to prepare sealing glass.The glass with composition of (60-x)SnF₂-xSnO-35P₂O₅-5WO₃ (x=0%,5%,10%,15%,20%,mass fraction) was prepared by high temperature melting method.The effect of SnO content on the structure and performance of the glass was studied.The internal structure of the glass was characterized by IR,and the thermal expansion coefficient and characteristic temperatures of the glass were measured.The results show that the addition of SnO to the composition introduces non-bridging oxygen to change the O/P atomic ratio,thereby affecting the glass structure and performance.With the increase of SnO content,the characteristic temperature,sealing temperature and water resistance of the glass are improved,and the coefficient of thermal expansion decreases.

Numerical Simulation of Throat in Optical Glass Electric Melting Furnace

GUO Fuqiang, HE Guang, PAN Zaiyong, CHEN Xiaoli, WANG Naishuai

2021, 40(1):  271-279. 

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The numerical simulation and analysis of throat in optical glass electric melting furnace was carried out by ANSYS 19.0 software.The flow distribution,temperature distribution and local backflow circulation were studied on different sizes of furnace throat design.The maximum backflow position of glass in the throat was analyzed,and then the number of local circulation loops in the throat and riser was described.The results indicate that multiple local circulation loops are found in the throat and riser,and the throat backflow circulation loops result in decreasing of glass forward flowing cross section and increasing glass velocity in z direction.Meanwhile,the backflow circulation loops also have a bad effect on the local temperature distribution of the throat,so that high temperature areas always close to the throat roof,which accelerate the erosion of roof.By reducing the width or height of throat,the recirculation ranges in the throat are reduced and the temperature uniformity of local glass have been improved.According to the curve fitting,there is no backflow circulation loops observed within the throat roof coverage area when the fixed height is 150 mm and the width is 108.14 mm or when the fixed width is 250 mm and the height is 77.57 mm.

New Functional Materials

Research and Application of Zeolite and Its Complex Gas Sensor

SUN Shupeng, SUN Yanhui, DONG Yuhua, HOU Tengyue, ZHENG Yangong, WANG Jing, ZHANG Zhaorui

2021, 40(1):  280-295. 

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As a common gas sensitive material,semiconductor metal oxide can be used as sensitive material to design gas sensors with different sensing principles.However,poor selectivity and sensitivity are always the shortcomings of this kind of gas sensors.In order to solve this problem,gas sensitive materials are often compounded with zeolite to prepare metal oxide/zeolite gas sensors,and improve the gas sensing characteristics of metal oxides with unique physical and chemical characteristics of the zeolite.In recent years,many researchers have studied the metal oxide/zeolite gas sensor,and the selectivity and sensitivity of this kind of sensor to target gas have been improved.In order to better summarize the existing research,focusing on the detection principle of gas sensors,this study concluded the metal oxide/zeolite gas sensors in combination with concluding the improvement of gas sensing characteristics by the zeolite,made a detailed arrangement and analysis from perspective of preparation method,gas sensing characteristics and sensitive mechanism of sensors,which provided a basis for the subsequent development of such work.

Preparation and Electromagnetic Wave Absorption Properties ofTi₃C₂T_x/Ni/TiO₂ Composite Powder

DU Heng, ZHANG Fan, SHEN Gang, QAIM Khan, FAN Kangkang, ZHANG Bihan, LI Ning, FAN Bingbing, ZHANG Rui

2021, 40(1):  296-303. 

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A two-dimensional layered Ti₃C₂T_x/Ni/TiO₂ composite powder was prepared by the heat treatment method.The samples were characterized and analyzed by TG-DSC,SEM,XRD and XPS.The electromagnetic parameters of the composite were measured by a vector network analyzer and its reflection loss(RL) under different coating thicknesses were calculated.The results show that the TiO₂ mass content in the product gradually increases as the heat treatment temperature increases.When the heat treatment temperature reaches 300 ℃,RL of the sample is -35.2 dB at f=17.5 GHz,and its effective absorption amplitude exceeds 1.7 GHz,corresponding to the thickness is 4 mm,and its excellent electromagnetic wave absorption performance due to the good impedance matching and the synergistic effect of the dielectric loss and magnetic loss of the sample.In addition,the sample electromagnetic wave absorption ability is modeled by their composition and microstructure.

Synthesis of N-Doped TiO₂/Fly Ash Composites by DemulsificationMethod and Its Visible Light Catalytic Performance

HU Kaiqiang, LAI Shengfa, QIAN Yanfeng, ZHANG Tiantian, QIAO Jiale, WAN Xianglong

2021, 40(1):  304-311. 

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The preparation of photocatalytic materials by loading TiO₂ on the surface of fly ash is a new way for high-value applications of fly ash.Loading TiO₂ on the surface of fly ash by demulsification method is a new attempt.Using fly ash modified with sodium dodecylbenzene sulfonate acted as the carrier,nano TiO₂ sol acted as the titanium source,NaOH used as the demulsifier,and urea acted as the nitrogen source,N-doped TiO₂/fly ash composite material was successfully synthesized in the reactor by the demulsification method.The products were characterized by scanning electron microscope (SEM),X-ray diffractometer (XRD),infrared spectrometer (FT-IR),and ultraviolet-visible diffuse reflectance spectrometer (UV-Vis DRS). The effect of photocatalytic materials on the visible light catalytic degradation of rhodamine B was tested.The results show that when the mass ratio of TiO₂ to fly ash is 1∶1 and the addition amount of urea is 0.5 g,the N-TiO₂/fly ash photocatalyst has a good degradation effect on rhodamine B under visible light. 96.98% of rhodamine B is degraded in 180 min and the degradation process conforms to the model of first-order kinetics reaction,it still has good stability and repeatability after 6 times of cycling utilization.This method provides a functional application scheme for high-value applications of fly ash and has a good application prospect.

Research on Rheological Properties of Vermiculite Based Casting Slurry

HU Shanhai, QIAN Yupeng, JIANG Xuefeng, WANG Fei, DING Feng, ZHAO Shaolin

2021, 40(1):  312-316. 

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Vermiculite based casting slurry was prepared using ball milling with modified expanded vermiculite and talc as raw materials,castor oil as dispersant,polyvinyl butyral (PVB) as binder and dibutyl phthalate (DBP) as plasticizer.The effects of solid dosages and amount of each component on the rheological properties of slurry were investigated.The suitable mass fraction components of tape casting slurry are obtained as follows:the solid dosage mass fraction of vermiculite powder is 50%,the castor oil dosage is 2%,the PVB dosage is 6%,and the DBP dosage is R=0.8.The casting slurry has plastic fluid characteristics with typical shear thinning behavior.The vermiculite based casting blank prepared by this formula has a uniform surface without cracks.

Preparation and Supercapacitor Performance of CoO@CuOElectrode Materials

WU Tong, GU Qingyu, WANG Peijian, LIU Zhongpin, SUN Haibin

2021, 40(1):  317-322. 

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Supercapacitors have attracted attentions due to many advantages,such as ultra-high power density,fast and stable charge/discharge rate,long cycle life and so on.CoO is regarded as a promising electrode of supercapacitor,the theoretical specific capacity reaches 4 292 F·g^-1,but its low conductivity and volume expansion during charge/discharge process lead to very low actual specific capacity than the theoretical specific capacity.In order to solve these problems,CuO nanowire arrays were firstly grown on copper foams via the thermal oxidation method.And then,hierarchical CoO was successfully deposited on CuO nanowires by chemical bath deposition,thus,core-shell CoO@CuO electrode materials were obtained.This electrode materials have an excellent specific capacity of 1.043 0 F·cm^-2 (117.145 3 F·g^-1) at the current density of 2 mA·cm^-2,as well as a good capacitance retention rate,which increase the number of surface active sites,reduce the effect of CoO volume expansion.

Refractory Materials

Effect of TiO₂ Content on Performences of AluminumMagnesium Dry Ramming Materials

XU Huan, WANG Xitang, ZHANG Wangnian, DENG Ning, LI Shibin

2021, 40(1):  323-329. 

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Aluminum magnesium dry ramming materials were prepared through heat treatment at 1 300 ℃,1 400 ℃,1 500 ℃ and 1 600 ℃ for 3 h,using fused white corundum,fused magnesia,reactive Al₂O₃ powder as main raw materials,and TiO₂ as clinkering aid.The effects of TiO₂ content,sintering temperature on the phase composition,sintering properties,mechanical properties and microstructures of aluminum magnesium dry ramming materials were investigated.The results show that the introduction of moderate amount of TiO₂ significantly promotes the reaction sintering of aluminum magnesium dry ramming materials,the mechanical properties both at normal and elevated temperatures are improved obviously.The strengthening of sintering performance is attributed to the formation of magnesium aluminum titanium phase and cation vacancy caused by the incorporation of TiO₂ into spinel lattice.Good comprehensive properties are obtained after heat treatment at 1 600 ℃ for 3 h when the TiO₂ content is 0.5%(mass fraction).At this time,the liner change rate is 3.7%,the bulk density and the porosity is 2.76 g·cm^-3 and 26.6 % respectively,the cold crushing strength is 18.9 MPa,and the HMOR is 1.9 MPa.When the content of TiO₂ is excessive,aluminate magnesium spinel materials show a large shrinkage as a result of excessive sintering,which is not conducive to the volume stability of the materials.

Road Materials

Macro-Meso Structure Performance of Foamed Asphalt Cold RecycledMixture with Different Curing Methods

WANG Yunan, LYU Weibang

2021, 40(1):  330-339. 

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In order to make the indoor accelerated curing method of foamed asphalt cold recycled mixture more realistically simulate the actual curing conditions in the field,based on the moisture content test,mechanical properties and fatigue test,the moisture content,splitting strength,penetrating shear strength and unconfined compressive strength of the foamed asphalt cold recycled mixtures with 5 curing methods were studied.And the differences in the early strength,medium and long-term mechanical strength,and fatigue performance of foamed asphalt cold recycled mixtures with different curing methods were compared.Then X-Ray CT was used as platform to study the distribution characteristics of the fine and microscopic three-dimensional void structure of foamed asphalt cold recycled mixtures with different curing methods.The test results show that the long-term mechanical strength and fatigue life of the five types of foamed asphalt cold recycled mixtures are ranked as follows:open curing >Marshall in-mold curing >semi-closed curing >combined curing >closed curing.There are obvious differences in the fine and microscopic void structure.The fine-micro void gradation,average void diameter,maximum void diameter,mechanical properties,and fatigue life of the foamed asphalt cold recycled mixtures are well fitted under different curing methods.The semi-closed curing condition at 40 ℃+36 h is recommended to simulate the early (from 7 d to 14 d) on-site curing conditions before the overlay is overlaid.The 40 ℃ semi-closed curing for 36 h+the fully closed curing for 72 h is used as the medium and long-term accelerated indoor curing method for foamed asphalt cold recycled mixture.

Discussion on Strength Characteristics and Mechanism of Cold MixAsphalt Mixture Based on Geopolymerization

ZHANG Yan, ZHOU Shengjie, FAN Liang

2021, 40(1):  340-349. 

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Based on the Marshall stability (M_S) strength evaluation index,the macro-strength test analysis of cold mix asphalt mixture was carried out under the conditions of different aggregate additives,water immersion and different curing ages,etc..The research on the microstructure of the aggregate surface and the compression mechanism of geopolymer were studied by fluorescence microscope and discrete element simulation methods.It is found that M_S of cold mix increases first and then decreases with the increase of geopolymer content.The M_S value reaches at peak when the mass ratio of base asphalt and geopolymer additives is 4∶3,and in the range of 4∶2 to 4∶3,the residual stability (MS0) has the smallest reduction meanwhile the strength loss rate reaches the lowest.It is concluded that the optimal mass ratio of base asphalt and geopolymer additives is 4∶3,and the strength increases with the increase of the curing age,while the growth rate of the strength gradually decreases.The curing time should not be less than 3 d.Through fluorescence microscope analysis,it is seen that the asphalt on the surface of the aggregate is glued by the geopolymer.Through the Marshall stability virtual test analysis,the main force direction of the specimen is located directly below the pressure bearing point,the aggregate is externally tensioned and internally compressed during the compression process,and the gelled geopolymer can better resist vertical load and improve the compressive strength of cold mix.