Table of Content

15 November 2021, Volume 40 Issue 11

Previous Issue    Next Issue

Cement and Concrete

Research Review of Magnesium Potassium Phosphate Cement Repair Materials

WANG Jianmiao, GAO Yueqing, ZHAN Peimin, ZHU Haonan, HE Zhihai, SANG Wei, MA Heheng

2021, 40(11):  3533-3543. 

Asbtract ( 324 )   PDF (9154KB) ( 168 )  

References | Related Articles | Metrics

Magnesium potassium phosphate cement (MKPC) is a kind of new cementitious material combined with chemical bonds, which has better properties than traditional Portland cement, and has already become one of the research hot spots of rapid repair materials. This paper introduces the research status of repair materials, summarizes the preparation and hydration process of MKPC, and discusses in detail the research progress of its workability, mechanical properties, durability, volume stability and crack repair. The existing problems in the current research are analyzed, and the development trend and application prospect in repair and reinforcement projects of MKPC are also pointed out.

Research Progress on Durability of Coral Concrete Reinforced with BFRP Bars

CHEN Hongmei, LIU Yutao, GUAN Jiwen

2021, 40(11):  3544-3555. 

Asbtract ( 107 )   PDF (5617KB) ( 84 )  

References | Related Articles | Metrics

With the increasing demand of building raw materials for the coastal engineering, it is obvious that the transportation of raw materials from inland to islands incurs high transportation costs and poor timeliness. For the construction of island and reef engineering, coral concrete can be mode from local available materials by using coral debris as aggregate and adding seawater. Fiber reinforced polymer (FRP) bars are used as structural reinforcement bars, which can effectively solve durability problems such as corrosion of steel in marine environment. However, basalt-fiber reinforced polymer (BFRP) bars with excellent mechanical properties are limited by short research time and insufficient theoretical experience in China. Therefore, a systematic study on enhancing the durability of BFRP bars reinforced coral concrete should be carried out to ensure the safety of island and reef engineering construction. Thus, based on the existing research progress, the basic mechanical properties of BFRP bars and coral concrete are analyzed respectively, then the durability of BFRP bars, the durability of coral concrete, the bonding durability of the interface between BFRP bars and coral concrete, and the structure durability of coral concrete with BFRP reinforced are systematically discussed and summarized. Finally, prospect of future research on enhancing the durability of coral concrete with BFRP bars is proposed.

Effect of Flaky Nano Boehmite on Mechanical and Microscopic Properties of Cement

ZHU Jianping, ZHU Lifei, FENG Chunhua, QUE Yongbo, SONG Weiyin, ZHANG Wenyan, YANG Kuo

2021, 40(11):  3556-3564. 

Asbtract ( 112 )   PDF (11509KB) ( 89 )  

References | Related Articles | Metrics

The addition of nanoparticles will affect the mechanical properties of materials. In this paper, flaky nano boehmite (FNB) was synthesized by the hydrothermal method in alkaline environment. The FNB was added to cement, and its influence on the mechanical properties of cement slurry was studied by hydration heat, X-ray diffraction, thermal analysis, nitrogen adsorption and scanning electron microscope. The results show that the addition of FNB obviously improves the early mechanical properties of cement paste, and when the content of FNB is 0.5% (mass fraction), the compressive strength of cement paste is increased by 42.8% to the maximum compared with the blank group. The addition of FNB can not only improve the hydration reaction rate of cement and promote the early hydration of cement, but also reduce the content of harmful pores, optimize the pore structure and improve the compactness of cement paste, thus promoting the development of early strength of cement. The research results provide a new method to improve the mechanical properties of cement paste.

Structure Analysis of Calcium Silicate Hydrate Polyurethane Nanocomposites Prepared by Hydrothermal Synthesis

YUAN Qi, HE Xiaofang, ZHANG Lihong, CAO Xinxin, FAN Shuaipeng

2021, 40(11):  3565-3571. 

Asbtract ( 87 )   PDF (9325KB) ( 69 )  

References | Related Articles | Metrics

In this paper, pure calcium silicate hydrate and calcium silicate hydrate polyurethane nanocomposites were synthesized by hydrothermal method using quicklime, nano silica and polyurethane as raw materials, and characterized by scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results show that there are obvious differences in microstructure between calcium silicate hydrate and calcium silicate hydrate polyurethane nanocomposites. With the increase of Ca/Si mole ratio, the tobermorite is discovered in the analysis results, and the crystallinity of this phase increases with the addition of polyurethane. Polyurethane can be embedded in the calcium silicate layer, and the distance between the base layers increases by 1.038 nm. The addition of polyurethane improves the thermal stability of calcium silicate hydrate, and the modification of calcium silicate hydrate with a high calcium silicon ratio is more effective.

Coupling Effect of Saline Solution and Freezing-Thawing Cycles on Performance of Basalt Fiber Reinforced Cemented Soil

XU Lina, ZHANG Runze, NIU Lei, SONG Daohan, JIN Yujie

2021, 40(11):  3572-3583. 

Asbtract ( 103 )   PDF (16443KB) ( 98 )  

References | Related Articles | Metrics

The effects of freezing-thawing cycles and erosion of external environment are the main factors affecting the strength of cemented soil. It is an important subject to explore how to improve the strength characteristics and development law of cemented soil under saline erosion environment in cold areas. Based on salt frozen and unconfined compressive strength test, the mechanical properties and apparent characteristics of basalt fiber reinforced cemented soil under the coupling of different solutions (3.5% (mass fraction, the same below) NaCl solution, 3.5%Na₂SO₄ solution, and mixed solution of 3.5% (NaCl+Na₂SO₄), freshwater solution) and freezing-thawing cycles were studied. The effects of the curing temperature, erosion solution type, and freezing-thawing cycle on the mechanical properties of the cemented soil were discussed. On this basis, the Logistic growth model was used to carry out a regression analysis on the strength of the cemented soil samples in different environments. The results show that the low-temperature curing environment inhibits the strength development of the cemented soil. As the number of freezing-thawing cycles increasing, the samples have different degrees of quality loss, surface damage and unconfined compressive strength decreases. With the same freezing-thawing cycles, the damage degree of basalt fiber reinforced cemented soil from strong to weak is sulfate frozen > mixed salt frozen > chloride salt frozen > water frozen. The addition of basalt fiber makes the cemented soil undergo more freezing-thawing cycles, effectively reduces the strength loss rate, and improves the frost resistance of the cemented soil. The regression analysis is used to obtain the intensity attenuation models and the expected strength of different test groups.

Change Rule of Porosity and Saturation of Cement Mortar under Sealed Curing Condition Based on Different Measured Methods

DING Qian, HUANG Yaoying, XU Xiaofeng, XIA Shifa, BAO Tengfei

2021, 40(11):  3584-3592. 

Asbtract ( 255 )   PDF (1648KB) ( 84 )  

References | Related Articles | Metrics

Porosity and saturation are important factors affecting the durability of concrete. To study the change rule of porosity and saturation of concrete in the state of moisture insulation, cement mortar specimens with different ages and different water-binder ratios were formed and cured under sealed condition. Then the porosity and saturation of specimens were measured by weighing method (WM), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR). The results show that the change rules measured by the three methods are consistent despite of slight differences in values. For the porosity, WM has the largest value, followed by NMR, and MIP has the smallest value. And for the degree of water saturation, the test value of NMR is higher than that of WM. The porosity of cement mortar first increases and then decreases with the age of 14 d as the boundary. The porosity of the specimen with a water-binder ratio of 0.41 is the largest and the maximum porosity is 39%. The saturation degree of cement mortar first decreases and then increases with the age of 14 d as the boundary. Higher water-binder ratio leads to higher degree of water saturation and the minimum saturation degree is 32%. Due to the randomness of the detection results of MIP, the detection results of WM and NMR are closer to the real porosity of the specimen.

Probability Distribution of Chloride Ion Concentration on Surface of Reinforcing Bar Based on Random Meso-Aggregate

CHEN Xuandong, RONG Hua, LIANG Miaomeng, YU Aiping, MING Yang

2021, 40(11):  3593-3600. 

Asbtract ( 72 )   PDF (7654KB) ( 31 )  

References | Related Articles | Metrics

Chloride ion erosion is one of the main factors leading to the durability failure of reinforced concrete (RC) structures. Thus, the study of the probability distribution of chloride ion concentration on the surface of reinforcing bar is of great significance to predict the service performance of marine engineering. By introducing the interface transition zone (ITZ) of random thickness, a concrete meso-model including aggregate, ITZ and mortar was established. Based on the theory of chloride ion diffusion, a meso-numerical model of chloride ion diffusion was established. The results show that the aggregate hinders the chloride ion diffusion and increases the chloride ion diffusion path. According to the statistical analysis of the chloride ion concentration on the surface of reinforcing bar surface by simulated 6 000 groups chloride ion diffusion, when the volume fraction of aggregate ratio is 40%, the chloride ion concentration on the reinforcing bar surface has a bimodal distribution and when aggregate ratio is lower than 40%, the chloride ion concentration on the reinforcing bar surface has a normal distribution. With the increase of aggregate ratio, the chloride iron concentration decreases and the coefficient of variation increases.

Meso-Research on Frost Resistance of Recycled Thermal Insulation Concrete

WANG Xianxing, LIU Yuanzhen, ZHAO Yu, DAI Xiaowei

2021, 40(11):  3601-3607. 

Asbtract ( 83 )   PDF (7561KB) ( 63 )  

References | Related Articles | Metrics

Due to the addition of recycled coarse aggregate and glazed hollow bead insulation aggregate, the complex pore structure is formed in recycled aggregate thermal insulation concrete (RATIC). In order to further reveal the deterioration mechanism of recycled thermal insulation concrete caused by freeze-thaw action, the crack development law and pore characteristics of RATIC specimens with different replacement rates of recycled coarse aggregate under freeze-thaw action were analyzed by CT scanning microscopic test based on the macro test. The test results show that the interface transition zone between new and old cement mortar is the weak link of RATIC under freeze-thaw cycles, and most cracks in the specimens originate from the interface transition zone between new and old cement mortar. The relative porosity of specimens is the best index to quantitatively reflect the internal failure law of RATIC specimens.

Research on Frost Resistance of Hybrid Fiber Reinforced Concrete Based on Fractal Theory of Pore Structure

WANG Chunxiao, DONG Jianming, LI Desheng

2021, 40(11):  3608-3616. 

Asbtract ( 72 )   PDF (1679KB) ( 44 )  

References | Related Articles | Metrics

In order to study the influence of fly ash content on the frost resistance of steel-polypropylene reinforced concrete, five kinds of hybrid fiber concrete with fly ash replacement rate were designed and prepared. The freeze-thaw cycle and salt-freeze cycle tests of concrete were carried out, the law of mass loss, dynamic modulus and bending toughness of the concrete as freeze-thaw cycles increase had been analyzed. Based on the thermo-dynamic model, the pore structure fractal dimension of concrete before and after freeze-thaw was calculated, and the relationship between fractal dimension and concrete bending toughness was established. The results show that when the fly ash content ranges from 5% to 15%, with the increase of fly ash content, the frost resistance of hybrid fiber concrete is improved obviously. With the increase of fly ash content to 20%, the residual flexural toughness of hybrid fiber concrete begins to decrease. The internal pores of hybrid fiber concrete have obvious fractal characteristics, and the fractal dimension has good linear correlation with the total pore proportion of harmless and less harmful pores and the pore proportion of more harmful pores. At the same time, the fractal dimension of the fiber reinforced concrete is positively correlated with the peak load and energy absorption value. The larger the fractal dimension is, the higher the peak load and energy absorption value the concrete can bear will be.

Experimental Study on Durability Degradation of Recycled Aggregate Concrete by Compound Salt Corrosion

HOU Zeyu, WANG Jiabin, GUO Qingjun, LI Heng, ZHANG Kaifeng

2021, 40(11):  3617-3626. 

Asbtract ( 90 )   PDF (9098KB) ( 60 )  

References | Related Articles | Metrics

There are a great number of corrosion ions in the soil and groundwater of Northwest China, which causing rapid degradation of durability of recycled aggregate concrete structures severely limit the application of recycled aggregate concrete in modern concrete structures. Based on the composition of corrosive ions and the characteristics of regional climate and environment in the durability environment of Northwest China, the experiment of durability degradation of recycled aggregate concrete subjected to compound salts was carried out by dry-wet cycles method with 7.5% (mass fraction) MgSO₄-7.5% (mass fraction) Na₂SO₄-5% (mass fraction) NaCl as the corrosive medium. The effects of mineral admixtures on durability of recycled aggregate concrete were studied by using active mineral admixtures such as fly ash, slag, silica fume and metakaolin instead of cement. And then, the mineral composition and relative content of mineral phases, and microstructures of corrosion products were characterized by XRD, FTIR, TG-DSC, SEM and EDS, respectively. In addition, the durability degradation process of recycled aggregate concrete was suggested. As the dry-wet cycles increase, the relative dynamic elastic modulus, mass change rate, relative compressive strength, relative splitting tensile strength, and damage depth are significantly related to the collocation of mineral admixtures. With the corrosion ions diffusing into concrete, the alkalinity of concrete decreases and the dense corrosion layers with brucite, gypsum and ettringite as the mainly corrosion products are successively formed on the surface of concrete, which temporarily hinders the further diffusion of corrosion ions. With the continuous accumulation of corrosion products and the formation of non-gelling products, the surface of recycled aggregate concrete is spalled and cracked under the combined action of expansion stress and salt crystallization pressure. The durability of recycled aggregate concrete is rapidly degraded.

Stress-Strain Relationship of Concrete after High Temperature in Initial Compaction Stage

WANG Lei, ZHAO Yanru, HAO Song

2021, 40(11):  3627-3633. 

Asbtract ( 81 )   PDF (1247KB) ( 52 )  

References | Related Articles | Metrics

Uniaxial compression tests were carried out on concrete after five temperatures (20 ℃, 200 ℃, 400 ℃, 600 ℃ and 800 ℃). The compaction coefficient φ and relative compactness Φ were defined to evaluate the compaction degree of concrete after high temperature. The variation law of initial compaction stage of concrete with temperature was discussed. A unified piecewise function was used to establish the full stress-strain curve equation of concrete after high temperature considering the initial compaction stage. The results show that when the temperature is 200 ℃ and 400 ℃, the peak stress and elastic modulus of concrete decrease slightly. The concrete has a high degree of compaction, and the initial compaction stage of the stress-strain curve is not obvious and can be ignored. The whole compression damage process is brittle. When the temperature is 600 ℃ and 800 ℃, the peak stress and elastic modulus decrease greatly, and the peak strain increases rapidly. The compaction degree of concrete decreases rapidly. The stress-strain curve has an obvious initial compaction stage. The whole compression damage process is ductile. The stress-strain full curve equation established in this paper has the advantages of high fitting degree and relatively few parameters.

Performance Evaluation Methods of Controlled Low-Strength Materials (CLSM)

WANG Wei, ZHANG Tongsheng, CHEN Canfeng, WU Zhengde, WEI Jiangxiong, YU Qijun

2021, 40(11):  3634-3643. 

Asbtract ( 278 )   PDF (4206KB) ( 132 )  

References | Related Articles | Metrics

Controlled low-strength material (CLSM) is a new filling material with high flowability, controllable and low strength, which is widely used in engineering backfills, pavement bases, conduit bedding and other projects. At present, there is no performance test method and standards for CLSM in China and it mainly draws lessons from the relevant evaluation methods of foreign standards and materials such as concrete and mortar, and it is urgent to formulate a reasonable, unified and systematic performance test method to standardize and promote the large-scale popularization and application of CLSM. This paper summarized the existing test methods of CLSM in terms of workability, mechanical properties, environmental impact and durability, and made a comparative analysis from the aspects of test principle, experimental parameters, advantages and disadvantages, so as to provide a basis for the performance test of CLSM and a reference for the formulation and perfection of CLSM standard system in China.

Solid Waste and Eco-Materials

Strength and Volume Stability of Controlled Low-Strength Material Based on Titanium Gypsum

ZHU Haoze, YU Fengquan, GENG Jian, WANG Xiangyang, QIN Huabin

2021, 40(11):  3644-3653. 

Asbtract ( 104 )   PDF (9121KB) ( 55 )  

References | Related Articles | Metrics

A new type of cementless titanium gypsum-based controlled low-strength material (CLSM) was proposed to solve the problems of low comprehensive utilization and insufficient consumption of titanium gypsum and poor compaction in road projects. The unconfined compressive strength test method and volume stability test method were used to study the effects of construction waste soil replacement rate, water-solid ratio, titanium gypsum content and activator content on the compressive strength and volume stability of CLSM, and the reasons for the properties changes through XRD and SEM were explored. The results show that the early strength of CLSM increases with the increase of the replacement of construction waste soil, but the expansion rate decreases. Increasing the water-solid ratio reduces the strength, and the expansion rate increases accordingly. However, increasing the content of titanium gypsum reduces the strength and expansion rate of CLSM. When the content of titanium gypsum is 70% (mass fraction), the volume of CLSM tends to shrink, and the shrinkage rate basically reaches the maximum at 14 d. The increase of the amount of quicklime improves the shrinkage of CLSM and plays a certain role in compensating for shrinkage.

Preparation and Performance of Desulphurized Gypsum-Based Sandless Self-Leveling Mortar

LIU Jingyu, SHAN Junhong, LI Chun, MIN Jiangning, DU Li, ZHOU Yuan

2021, 40(11):  3654-3661. 

Asbtract ( 115 )   PDF (3415KB) ( 47 )  

References | Related Articles | Metrics

The desulphurized gypsum-based sandless self-leveling mortar was prepared by desulphurized building gypsum, P·O 42.5 cement, fly ash, limestone ultrafine powder and admixtures as raw materials. The optimal ratio of gypsum-based cementitious material was determined by orthogonal test. The effects of retarder and cellulose ether on the performance of gypsum-based sandless self-leveling mortar were studied. XRD and SEM were used to analyze the hydration products and microstructure of the system, and the mechanism of the admixtures was further studied through the analysis results. The results show that when the mass ratio of desulfurized gypsum, cement, fly ash and limestone ultrafine powder is 16:1:2:1, the strength of material is optimal. The retarder significantly prolongs the setting time of the mortar, but it causes bleeding of the mortar. Cellulose ether improves the water retention of the mortar, but the strength of mortar decreases due to the air-entraining of cellulose ether. The performance of desulfurized gypsum-based sandless self-leveling mortar meets the requirements of “Gypsum-based self-leveling mortar (JC/T 1023—2007)”.

Effect of Particle Size Classification on Purification of Vein Quartz

LIU Yuhang, REN Zijie, GAO Huimin, GUAN Junfang, MA Junhui, WU Feida

2021, 40(11):  3662-3667. 

Asbtract ( 80 )   PDF (4230KB) ( 55 )  

References | Related Articles | Metrics

Vein quartz is a kind of high quality silicon resource as an ideal raw material for processing high purity quartz. The process mineralogy of vein quartz was studied. The differences of samples with different size fractions after crushing or grinding were also analyzed. The experiments of iron removal by magnetic separation and feldspar and mica removal by flotation were carried out on four samples of -0.6+0.1 mm grade, -0.1+0.045 mm grade of raw material and -0.6+0.1 mm grade, -0.1+0.045 mm grade of grinding product, respectively. The results show that the vein quartz mainly consists of large quartz grains and the gangue is mainly muscovite, feldspar and a small amount of iron minerals. The content of SiO₂ in -0.6+0.1 mm grade, -0.1+0.045 mm grade of raw material and -0.6+0.1 mm grade, -0.1+0.045 mm grade of grinding product are increased from 99.10% to 99.62%, 99.74%, 99.67% and 99.66%, respectively. And the contents of Fe₂O₃ in each sample are decreased from 609.55 μg/g to 70.26 μg/g, 69.90 μg/g, 38.64 μg/g and 40.33 μg/g respectively. In general, the purification effect of -0.6+0.1 mm grade of the grinding product is the best, showing that the classification separation process is beneficial to the purification of vein quartz.

Preparation and Performance of Polymer Based on Shale Vanadium Extraction Tailings

XU Xianqing, BAO Shenxu, ZHANG Yimin, LUO Yongpeng

2021, 40(11):  3668-3676. 

Asbtract ( 84 )   PDF (3572KB) ( 90 )  

References | Related Articles | Metrics

In order to use shale vanadium extration tailings (vanadium tailings) as resources, the vanadium tailing was used as the main raw material and the metakaolin was used as an aluminum auxiliary material to prepare geopolymers. The effects of molding method, silicon-aluminum raw material ratio, alkali activator type, alkali activator dosage and molding pressure on the compressive strength of geopolymer samples were investigated. The test results show that the best conditions for the preparation of geopolymers: the quality ratio of raw materials (tailings/metakaolin) is 11:9, the mass fraction of NaOH alkali activator is 10%, the water-solid ratio is 0.18, and the molding pressure is 20 MPa. The compressive strength of the geopolymer after curing for 14 d reaches 58.25 MPa. The geopolymer samples were detected and characterized by XRD, FTIR, TG-DSC, SEM and pore size analysis. The results show that the main products of the geopolymerization reaction are amorphous silica-alumina gel and a small amount of sodium zeolite. Amorphous silica-alumina gel can improve the pore structure of samples and enhance the density of the microstructure of samples, resulting the increase of compressive strength of samples in macroscopic scale.

High Temperature Resistance of Accelerated Carbonated Steel Slag Blocks

ZHONG Xinzhuo, LI Lufan, JIANG Yi, LING Tungchai

2021, 40(11):  3677-3684. 

Asbtract ( 105 )   PDF (7107KB) ( 85 )  

References | Related Articles | Metrics

In order to develop steel slag for high temperature environments and improve the comprehensive utilization rate as much as possible, compressive strength, mineral phases, and microstructure of accelerated carbonated steel slag blocks cured with different high temperatures were investigated in this study by strength test, TGA, XRD and SEM. The results show that the compressive strength of accelerated carbonated steel slag blocks is improved when exposed to high temperature between 200 ℃ to 600 ℃, and the highest compressive strength of 72.4 MPa is obtained at 400 ℃, which is 20.5% higher than the initial compressive strength. The content of calcium silicate at 400 ℃ is reduced, C-S-H net structure is observed, which confirmed the further hydration of calcium silicate. The hydration product enhances the matrix connection, resulting in strength improvement. The performance of steel slag degrades at 800 ℃ and the strength reduces 90.7% of initial strength. The mass fraction of calcium carbonate reduces from 24.1% to 1.6%. The total mass loss reaches 19.67% and the water absorption improves significantly. Cracks through the blocks are also investigated. The high temperature resistance of accelerated carbonated steel slag blocks is better than cement-based materials, but the advantage is not obvious when the temperature reaches 800 ℃.

Influence of SrO on Properties of Clinker in Cement Production with Solely Waste Slags

SONG Xiaoling, TANG Jianjian, XU Panpan, YANG Zhong, HUANG Dong, HU Jingping, ZHANG Kun, LUO Guangqian, HOU Huijie, LIU Bingchuan

2021, 40(11):  3685-3692. 

Asbtract ( 99 )   PDF (6300KB) ( 44 )  

References | Related Articles | Metrics

The technology of dry cement production with solely waste slags developed by Xinjiang Tianye (Group) Co., Ltd uses 100% calcium carbide slag from PVC industry, lime residue, dedusting ash and more than ten types of other waste slags to manufacture cement, implementing the full resource utilization of industrial solid waste. It is found that the raw materials contain a small amount of SrO, which may affect the properties of clinker. By using chemical composition analysis, X-ray diffraction and Rietveld full spectrum fitting, the raw meal and clinker were analyzed, and the mechanical strength of clinker was tested. With varied content of SrO in raw meal, the changes of mineral phases and liquid phase were simulated with a thermodynamic simulation software. The results show that the additional of a small amount of SrO into raw meal can promote the formation of C₃S, C₄AF and other mineral phases, and greatly improve the early mechanical strength of clinker. However, the effect on the later strength is not so obvious.With the increase of SrO content, the content of C₃S in clinker increases, which is beneficial for the formation of iron minerals, but the content of free calcium oxide increases. Therefore, it is necessary to control the addition of SrO and the mass fraction of SrO between 0.2% and 1.0%, which is beneficial for the clinker quality.

Influence of PVA Fiber Type on Mechanical Properties of Strain-Hardening Geopolymer Composites

ZHU Hongkang, LIN Chang, CAI Shu, XU Shuying, PAN Lisha

2021, 40(11):  3693-3701. 

Asbtract ( 153 )   PDF (7406KB) ( 77 )  

References | Related Articles | Metrics

The toughening effects of four types of polyvinyl alcohol (PVA) fibers in geopolymer matrices with different mix proportions were investigated, which can provide experimental data for the preparation of strain-hardening geopolymer composites (SHGC) reinforced with domestic PVA fibers without surface oil coating. The focus was on the influences of the ratio of slag to fly ash, concentration of alkaline solution, dimensions and surface properties of fibers and the like on the compressive and direct tensile properties of SHGC. The compressive testing results show that the matrices and composites containing slag have a compressive strength more than 30 MPa, and those with plain fly ash ranging from 12 MPa to 15 MPa. The direct tensile testing results show that the ductility of SHGC with oil-coated PVA fibers is generally higher than that of SHGC with non-oil-coated PVA fiber. However, the toughening effect of domestic PVA fibers can be enhanced by tailoring the mix proportion of matrices. For the case where the dosage of fly ash is 33% (by mass), SHGC reinforced with non-oil-coated PVA fibers displays a value in ultimate strain up to 1.44%, comparable with that of SHGC with oil-coated PVA fibers. For the case of plain fly ash, geopolymer composites reinforced with any one of the four types of PVA fibers exhibit stable multiple cracking and strain-hardening behavior.

Influence of Alkaline Electrolyzed Water with Different pH Values on Workability and Strength of Mortar

XIE Zixi, LIU Guibin, ZHANG Tianyu, LI Qiuyi, WANG Liang

2021, 40(11):  3702-3711. 

Asbtract ( 97 )   PDF (6903KB) ( 43 )  

References | Related Articles | Metrics

Alkaline electrolyzed water has the advantages of strong alkalinity, high activity, ionicity and adsorption. In this study, alkaline electrolyzed water with different pH values (9.5, 10.5, 11.5) was used to prepare fly ash mortar, under the conditions of 0%, 15% and 30% (mass fraction) replacement rate of fly ash, the influence of alkaline electrolyzed water with different pH values on the workability, mechanical properties and the Ca(OH)₂ content of cement hydration products of fly ash mortar was systematically studied. And the structure composition and micro morphology of fly ash paste with different pH values were compared and analyzed by XRD, SEM and other microscopic tests. The test results show that compared with fly ash mortar with ordinary tap water, with the increase of pH value, the fluidity, compressive strength and flexural strength of alkaline electrolyzed water fly ash mortar gradually increase, and the content of hydration product Ca(OH)₂ gradually reduces. When the pH value of alkaline electrolyzed water is 10.5 and the fly ash replacement rate is 15%, the improvement effects of the early strength and fluidity of alkaline electrolyzed water fly ash mortar reach the best, and compared with ordinary tap water mortar, the compressive strength and flexural strength at 28 d increase by 8.4% and 12.5%, respectively. At the same time, compared with ordinary tap water fly ash-cement paste, the clustering and granulation of alkaline electrolyzed water fly ash-cement paste with different pH values are more obvious, which can play a positive role to promote the cement hydration process, improve the fluidity of the mortar, and stimulate the early activity of fly ash. In addition to generating more hydration products such as C-S-H gel and Ca(OH)₂,other hydration products such as potassium feldspar are also generated.

Proportion and Performance of Grouting Materials Prepared by Red Clay Slag in Karst Area

ZHANG Yi, DENG Bianyuan, ZHANG Yanjie, GUI Yue

2021, 40(11):  3712-3722. 

Asbtract ( 81 )   PDF (10387KB) ( 52 )  

References | Related Articles | Metrics

During the construction of bored piles in karst area, grouting method can effectively improve the problems such as easy loss of concrete, broken pile, holes in pile body and so on, but the cost of traditional grouting materials is high and the performance is excessive; on the other hand, there are often a lot of abandoned slag in the construction site that need to be properly disposed of. A new type of grouting material was prepared by using red clay slag as base material, cement and fly ash as main curing agents and sodium silicate as auxiliary. Through the orthogonal test, the influence of each component on the key performance index of slurry was explored, the optimum proportion was determined, and the microstructure of slurry stone body under the optimal proportion was analyzed. The results show that the water-soil ratio is the main factor affecting the performance of slurry. The content of cement has the greatest influence on the strength of slurry stone body. The fly ash increases the concretion rate of slurry and improves the later strength of stone body. The sodium silicate mainly plays a role in accelerating setting. The optimal proportion of slurry is water-soil mass ratio of 0.6, cement content of 10% (mass fraction), fly ash content of 12% (mass fraction) and sodium silicate content of 1.1% (mass fraction). After comprehensive analysis, the slurry has the characteristics of high fluidity, good fallibility, moderate strength and low cost, which meets the large-scale use of the engineering.

Effect of Water-Binder Ratio on Working Performance and Mechanical Properties of Recycled Brick Powder ECC

YUAN Chengfang, LI Haofei, WANG Di, WANG Yiguang

2021, 40(11):  3723-3729. 

Asbtract ( 69 )   PDF (3955KB) ( 50 )  

References | Related Articles | Metrics

The recycled brick powder was used to replace quartz sand to prepare engineered cementitious composites (ECC). The working performance and mechanical properties of materials were studied and analyzed, and the related mechanism was discussed by scanning electron microscopy. The research shows that when the water-binder ratio changes from 0.30 (mass ratio, the same below) to 0.39, the slump of recycled brick powder ECC mixture is above 200 mm, and the working performance is good. Under the same water-binder ratio, the mechanical properties of ECC decrease after replacing quartz sand with recycled brick powder. When the water-binder ratio ranges from 0.30 to 0.37, the flexural strength of recycled brick powder ECC increases with the increase of water-binder ratio. When the water-binder ratio ranges from 0.30 to 0.39, the compressive strength of recycled brick powder ECC decreases with the increase of water-binder ratio. The recycled brick powder ECC in each group show good strain hardening characteristics, showing multi-crack cracking state, and the ultimate strain is greater than 2%. Under the experimental conditions in this paper, the flexural and uniaxial tensile properties of 0.37 water-binder ratio recycled brick powder ECC are the best.

Ceramics

Research Progress on Synthesis and Application of Lanthanide Germanates

HAO Xiandong, QIU Hongju, GUI Yuxi, DUAN Liping, CHEN Guo, GAO Lei

2021, 40(11):  3730-3739. 

Asbtract ( 227 )   PDF (5780KB) ( 125 )  

References | Related Articles | Metrics

As an important strategic resource, rare earth is one of the key materials needed in high precision industry. Lanthanide germanate is a variety of rare earth functional materials, it has 4f electronic structure and O-Ge tetrahedral structure which are similar to rare earth functional materials and silicate. Lanthanide germanate also has the physical and chemical properties and structural characteristics of rare earth functional materials and silicate, which has received extensive concern and study at domestic and overseas. At the moment, lanthanide germanates show excellent physical and chemical properties such as optical, electrical, magnetic and ferroelectric properties, and have a better application prospect in related fields. In this paper, the synthesis methods and research status of lanthanide germanates were reviewed. The preparation of lanthanide germanates by high temperature solid method, flux method, hydrothermal synthesis method and complex method were discussed emphatically, the applications of lanthanide germanates in luminescent materials, photocatalytic materials and solid electrolyte were introduced. Then the development tread and application domain of lanthanide germanate preparation technology were prospected.

Preparation and Electrochemical Performance of SnO₂ Supported on Porous Bamboo Charcoal

WU Hong, CHEN Qianlin, LI Cuiqin

2021, 40(11):  3740-3749. 

Asbtract ( 84 )   PDF (14857KB) ( 56 )  

References | Related Articles | Metrics

Porous bamboo charcoal is amorphous carbon with abundant pore structure, and the pore size ranges from 1 nm to 6 nm, with a large pore volume (1.21 cm³/g). Using porous bamboo charcoal as the carrier, the B₂O₃-SnO₂/C composite material was prepared by the sol-gel method. SEM and TEM results show that SnO₂ and B₂O₃ are uniformly distributed on the surface of the porous bamboo charcoal. The porous bamboo charcoal and B₂O₃ effectively accommodate the volume change of the reversible reaction of SnO₂ and improve the cycling stability of SnO₂. The lithium-ion batteries were assembled by B₂O₃-SnO₂/C composite materials as anode, and the electrochemical performance was tested. After 200 cycles, the discharge specific capacity still reaches 649.9 mAh/g at 1 C (1 C=372 mA/g) rate, and the discharge specific capacity retention rate is as high as 58.6%. The charge-discharge process of B₂O₃-SnO₂/C porous composites is controlled by diffusion and capacitance behavior, and the contribution rate of capacitance control increases with the increase of scan rate.

Preparation and Photocatalytic Performance of Bi and Co Doped TiO₂ Ceramic Films

TIAN Qingquan, LI Peiying, CAO Panting, YU Qiangxia

2021, 40(11):  3750-3755. 

Asbtract ( 89 )   PDF (8628KB) ( 67 )  

References | Related Articles | Metrics

Bi-TiO₂ and Co-TiO₂ composite films applied on the fixed photocatalytic reactor were prepared on ceramic substrate by sol-gel method, with the titanium source of tetrabutyl titanate, the Bi source of Bi(NO₃)₃·5H₂O and the Co source of Co(NO₃)₂·6H₂O. The effects of coating processes and heating rates of calcination on the surface morphology of the films were studied.The photocatalytic activity of the films prepared by spin-coating method and dip-coating method at different heating rates was compared with methyl orange solution. The structures of the films were conducted by TG-DSC, XRD and SEM tests. The results show that Bi or Co ion doping are beneficial to the phase transformation of amorphous TiO₂ to anatase TiO₂.The results show that the films prepared by spin-coating method are closely bonded to the ceramic substrate, while the films prepared by dip-coating method have higher catalytic activity. When the calcination temperature is 500 ℃ and the heating rate is 10 ℃/min, the degradation rate of methyl orange is higher. When the atom mole ratio is 0.010, the photodegradation of methyl orange catalyzed by the Bi-TiO₂ films is up to 8.10% after 100 min reactions. Co or Bi ion-doped process are able to improve the photocatalytic activity of the TiO₂ catalyst and the catalytic activity of Bi-TiO₂ films is better than that of Co-TiO₂ films.

Influence of HNO₃ on Rheological Properties of AlOOH Sol

ZHANG Xiangtai, DUAN Ning, LU Chenglong, ZHANG Yinfeng, LI Chongrui

2021, 40(11):  3756-3761. 

Asbtract ( 66 )   PDF (3520KB) ( 62 )  

References | Related Articles | Metrics

In order to control the coating process in the preparation of alumina ceramic membrane, AlOOH sol was prepared by using aluminum isopropoxide as the raw material and HNO₃ as the peptizer. The influence of the amount of HNO₃ on the rheological properties of AlOOH sol was studied through rotational rheometer and Zeta potential measurement. The results show that when the molar ratio of HNO₃ to aluminum isopropoxide R(n(HNO₃):n(Al(C₃H₇O₃)₃)) is in the range of 0.3 to 0.6, AlOOH sol exhibits pseudoplastic fluid characteristics. The Herschel-Bulkley model was used to fit the rheological test data. As R increases, the fluid index (n) decreases, while the consistency coefficient (k_HB) increases. The storage modulus (G′) and loss modulus (G″) increase with the increase of R. The intersection of G′ and G″ in the frequency sweep gradually approaches the low frequency with the increase of R. With the increase of R, the pseudoplasticity of AlOOH sol increases, the consistency increases, the elasticity and viscosity both increase, and it is easier to gelation. While R is above 0.7, it has been transformed into a gel, which does not conform to the fluid law. The level of the Zeta potential affects the dispersibility of the AlOOH sol, thereby affects the above phenomenon.

Catalytic Degradation of Malachite Green by SrFe_0.6Co_0.4O₃

LI Jiafei, XU Kai, ZHANG Yongming, PAN Lisha

2021, 40(11):  3762-3768. 

Asbtract ( 57 )   PDF (5152KB) ( 59 )  

References | Related Articles | Metrics

Malachite green (MG) is a triphenylmethane dye with a complex molecular structure, which is difficult to be degraded, and it makes a difficulty in industrial wastewater treatment. In this paper,based on Goldschmidt radius tolerance rule, the ABO₃ type catalysts with formula SrFe_(1-x)Co_xO₃ (x=0～1) for degrading MG was designed. After experimental investigation, the SrFe_0.6Co_0.4O₃ with highest catalytic activity was selected as target catalyst for MG degradation. The characteristics of this catalyst were analysed by XRD, SEM, BET and XPS methods. XRD pattern shows that the catalyst is pure perovskite crystal; the SEM image shows the morphology of catalyst particles is “honeycomb” flake with irregular stacking. In the BET adsorption isotherm of the catalyst, there is no obvious hysteresis loop, which means that there is no pore like “ink bottle”. Seeing from the XPS spectrum of the catalyst, the B-position has four ions (Fe²⁺/Fe³⁺ and Co²⁺/Co³⁺) at the same time, and the distribution ratio of above four ions vary greatly before and after the catalytic reaction. Based on these results, the mechanism of the catalytic reaction is speculated as follow: at first the Co³⁺ on B-site with the dissolved oxygen to form active oxygen [O₂]⁺ and Co²⁺; then the [O₂]⁺ oxidizes the MG, as well as the positive charge of [O₂]⁺ is transferred to the Fe²⁺ on B-site to form Fe³⁺; at last, the positive charge of Fe³⁺ could be transferred to Co²⁺ on the B-site to form Co³⁺, and the transfer and circulation of the charge in catalytic process is completed.

Density Functional Calculation of La(H₂O)³⁺₁₀ Adsorption on Surface of Montmorillonite (001)

YAO Xiaohui, HUANG Lijinhong, HUANG Wanfu, ZENG Xiangrong, HUANG Biaolin, BAO Yaqing

2021, 40(11):  3769-3776. 

Asbtract ( 70 )   PDF (5022KB) ( 58 )  

References | Related Articles | Metrics

In order to study the effect of the interaction between the (001) surface of montmorillonite and the hydrated rare earth La ion La(H₂O)³⁺₁₀ on the adsorption of La(H₂O)³⁺₁₀ on the surface of montmorillonite. The adsorption energies of La(H₂O)³⁺₁₀ on Na-(001) (the surface of containing sodium ions) and None-(001) surface (the surface without sodium ions) of montmorillonite were calculated respectively, including the density of states, electrons transference and interacting intensity of the nearest atoms. The results show that the adsorption energy of Na-(001) surface with Na ion is greater, and the adsorption of La(H₂O)³⁺₁₀ on Na-(001) surface is more stable. There is a certain interaction between O_w (oxygen atoms in a hydrated water molecule) in La(H₂O)³⁺₁₀ and O_f (oxygen atoms exposed to the surface) in Na-(001) surface, and O_f in None-(001) surface and H_w (hydrogen atoms in water molecules) in La(H₂O)³⁺₁₀, and the charge transferred from La to Na-(001) surface (0.44 e) is more than that from None-(001) surface (0.16 e). The intensity of Na—O_w is stronger than that of O_f—H_w, and the adsorption strength of La(H₂O)³⁺₁₀ on the montmorillonite (001) is stronger than that on None-(001). It can be inferred that the interlayer cation Na enhances the adsorption strength of La(H₂O)³⁺₁₀ on the montmorillonite (001) surface.

Effects of Metal Aluminum Powder and Nano-Al₂O₃ Powder on Properties of Vitrified Bond

LI Junjun, WANG Yunfeng, ZHANG Aiju, LI Zicheng, PANG Tongjun, LI Zhihong

2021, 40(11):  3777-3783. 

Asbtract ( 82 )   PDF (5354KB) ( 61 )  

References | Related Articles | Metrics

Metal aluminum powder and nano-Al₂O₃ powder were added to the basic vitrified bond. The glass structure was analyzed by infrared spectroscopy, the phase change was characterized by X-ray diffraction, and the refractoriness of vitrified bond was tested. The microstructure of vitrified bond CBN composite was analyzed by scanning electron microscope, and the bending strength of composite was tested. The effects of single doping and compound doping with metal aluminum powder and nano-Al₂O₃ powder on the performance of vitrified bond were systematically analyzed. The results show that the refractoriness of vitrified bond increases by adding metal aluminum powder, and the glass structure dose not change significantly. After sintering, part of the metal aluminum powder is transformed into Al₂O₃, and the bending strength of vitrified bond CBN composite increases with the increase of sintering temperature. The refractoriness of vitrified bond is reduced by adding nano-Al₂O₃ powder, and the vitrified bond is in glass phase, but a small amount of Al₂SiO₅ and Li_xAl_xSi_3-xO₆ crystals are precipitated, and a higher bending strength of 93.7 MPa of vitrified bond CBN composite is obtained sintering at 720 ℃. Compound doping of metal aluminum powder and nano-Al₂O₃ powder is beneficial to bonding of glass network structure. The vitrified bond is mainly glass phase, but a small amount of crystals are precipitated. Compound doping is more beneficial to increase bending strength of vitrified bond CBN composite, but the sintering temperature also increases accordingly. The highest bending strength of the composite sintered at 740 ℃ is 97.4 MPa.

Glass

Femtosecond Laser Direct Written Waveguides in Ultra-Low Expansion Glass-Ceramics

LI Zihuang, GAO Yunzhou, FAN Shigang, GU Shaoxuan, TAO Haizheng

2021, 40(11):  3784-3790. 

Asbtract ( 95 )   PDF (12264KB) ( 111 )  

References | Related Articles | Metrics

Basing on optimized laser parameters, optical waveguides with an insertion loss of 4.94 dB were fabricated in ultra-low expansion glass-ceramics by using femtosecond laser to directly write waveguide method. The structure and transmittance of the glass-ceramics before and after laser irradiation were characterized by Raman spectrometer, X-ray diffractometer and spectrophotometer. The cross-section morphology and element distribution of samples were characterized by SEM and EDS. Based on the 2% (mass fraction) HF dilute solution corrosion test, the chemical corrosion resistance of samples was characterized. The valence states of zirconium and titanium ions in samples were characterized by X-ray photoelectron spectroscopy. The results show that after laser irradiation the chemical corrosion resistance of glass-ceramics decreases, some small and obvious absorption bands appeares in glass-ceramics. Combined with X-ray photoelectron spectroscopy analysis, it is confirmed that these phenomena are caused by the reduction of Zr⁴⁺ or Ti⁴⁺ in glass-ceramics into meta-stable Zr³⁺ or Ti³⁺ with higher chemical activity.

Preparation and Optical Properties of Co²⁺-Doped ZnO-MgO-Al₂O₃-SiO₂ System Glass-Ceramics

ZHANG Tao, HOU Zhengzheng, JING Tao, LI Sheng, GUO Yanxing, JIAO Zhiwei

2021, 40(11):  3791-3798. 

Asbtract ( 84 )   PDF (2899KB) ( 67 )  

References | Related Articles | Metrics

In this paper, transparent glass-ceramics of the Co²⁺-doped ZnO-MgO-Al₂O₃-SiO₂ (ZMAS) system were prepared via melting method and heat-treatment. Based on the X-ray diffraction results, it determine that the main crystalline phase of glass-ceramics is ZnAl₂O₄/MgAl₂O₄, and the composition of the glass-ceramics don't change significantly with the increase of the crystallization treatment time. The crystallinity and the average grain size of spinel increase first and then decrease. It shows that the broad absorption band of ⁴T₁(⁴F)→⁴A₂(⁴F) transitions and the emission peak of ⁴T₁(⁴P)→⁴A₂(⁴F) transitions of tetracoordinated Co²⁺ do not appear in both the absorption spectra and emission spectra of glass-ceramics. This indicates that Co²⁺ enter the spinel phase ZnAl₂O₄/MgAl₂O₄ and replace Zn²⁺ or Mg²⁺ in the tetrahedral (T_d) sites. With the increase of crystallization treatment time, the absorption spectral intensity and emission spectral intensity of the samples increase first and then decrease. This is consistent with the changing trend of X-ray diffraction results. It shows that the optical properties can be controlled by controlling the crystallinity of glass-ceramics, which has certain guiding significance for the preparation of glass-ceramics with good properties. Comparing the glass-ceramics prepared by using raw materials with different valence states of Co oxides the result shows that the element Co exists as divalent Co²⁺ in the spinel phase of the final glass-ceramics, whether it is doped with CoO or Co₂O₃. Moreover, the prepared glass-ceramics material was compared with other Co-doped matrix materials in terms of the ground state absorption cross section (σ_gas) at 1 540 nm, showing that it can be used as a saturable absorber in Q-switch lasers.

Mechanism of Compound Refining Agents for TFT Substrate Glass Melting Process

HUANG Yiping, SHU Zhongzhong, CAO Zhiqiang, ZHANG Xiaodong, ZHANG Chong, JIN Liangmao, SHEN Yuguo

2021, 40(11):  3799-3806. 

Asbtract ( 123 )   PDF (3686KB) ( 75 )  

References | Related Articles | Metrics

Aiming to better understand the mechanism of refining agents for thin film transistor (TFT) substrate glass melting process, the proper temperature and refining effect of SnO₂, CaSO₄, NaCl and their compounds in melting process were studied by simulating float melting technology of TFT substrate glass. A high temperature melting dynamic observation was also used to study the detailed melting process. The effect of the NaCl amount used on the thermal properties of glass and the residual Na⁺ content in glass was discussed. The results show that the appropriate amount of SnO₂ is 0.10% (mass fraction) as a single refining agent. The further investigations on the compound refining agents indicate that the gradient clarification composed of 0.10% (mass fraction) SnO₂ and 0.35% (mass fraction) CaSO₄ has the best refining performance. For the synergy clarification composed of SnO₂ and NaCl, the refining performance increases with the increase of the amount of NaCl, but it should not exceed 0.076 3% (mass fraction) to satisfy the strict requirements of TFT substrate glass. The above research results offer important information for improving melting technology and product quality of TFT substrate glass, and they are beneficial to reduce cost and increase efficiency for the related industrial production.

Effects of Alkali Metal Oxides on Structure and Properties of Sealing Glass with Low-Dielectric Constant

LI Jinwei, WANG Weiwei, ZHONG Zhaojin, WANG Pingping, SHI Lifen, GUAN Min, YU Tao, CAO Xin

2021, 40(11):  3807-3812. 

Asbtract ( 127 )   PDF (1903KB) ( 83 )  

References | Related Articles | Metrics

Glass is widely used in the field of electronic sealing due to its excellent electrical properties. The low dielectric sealing glass was prepared by high temperature melting method under aluminoborosilicate glass. The properties of the samples were characterized by Raman spectroscopy, thermal expansion coefficient tester, densitometer, bending beam low temperature tester and precision impedance analyzer. The effect of alkali metal oxides on the structure and properties of low dielectric glass was studied. The result shows that when the total content of R₂O remains unchanged, with the increase of Li₂O content, the content of [BO₃] in the glass structure decreases first and then increases, the content of [AlO₄] increases and the content of [AlO₆] decreases. The thermal expansion coefficient of glass decreases first and then increases, and the trend of density change is opposite to the thermal expansion coefficient. All of the above variables have extreme values in the LN-3 (the mass ratio of Na₂O and Li₂O is 1.0:1.0) group. The characteristic temperature of glass increases first and then decreases, and finally increases again when Na₂O is completely replaced. The dielectric constant and dielectric loss of glass decrease first and then increase, and the dielectric constant and dielectric loss of the glass containing mixed alkali metals are lower than that of the glass containing single alkali metal.

Influence of Mixed Alkali Effect on Structure and Thermal Expansion Properties of Li₂O-Al₂O₃-SiO₂ Glass

ZENG Lin, HUANG Shoujia, LIN Hongjian, ZHAO Huifeng, JIANG Hong, MA Yanping

2021, 40(11):  3813-3821. 

Asbtract ( 117 )   PDF (4416KB) ( 77 )  

References | Related Articles | Metrics

In this paper, the Li₂O-Al₂O₃-SiO₂ high alumina glass was melted by traditional high temperature melting method, and the mole ratio of alkali metal oxide n(Li₂O)/n(Na₂O) was changed. The influence of mixed alkali metal effect on the structure and thermal expansion performance of Li₂O-Al₂O₃-SiO₂ glass was investigated by Archimedes drainage method, thermal expansion instrument, DSC, Fourier transform infrared spectroscopy and Raman spectroscopy. The effects on the structure and thermal expansion properties of Li₂O-Al₂O₃-SiO₂ glasses are different. Results show that with the increase of n(Li₂O)/n(Na₂O) mole ratio, the mixed alkali metal effect has the same effect on the density and thermal expansion coefficient of Li₂O-Al₂O₃-SiO₂ glass, which increases first and then decreases, When R=0.25(R=n(Li₂O)/[n(Li₂O)+n(Na₂O)], mole ratio) has a maximum value, the maximum density is 2.447 4 g/cm³, and the maximum thermal expansion coefficient is 7.811 7×10^-6/℃. The influence on the characteristic temperature of glass gradually weakens and disappears with the increase of temperature. It can promote the crystallization behavior of glass to some extent.The influences on the silicon-oxygen tetrahedron Qⁿ in the three-dimensional skeleton structure of glass are also different.

Theory and Analysis of Glass Indentation Stress Field of Tempered Vacuum Glass with Spherical Support

LIN Haixiao, LIU Zhihong, YUE Gaowei

2021, 40(11):  3822-3828. 

Asbtract ( 97 )   PDF (8089KB) ( 63 )  

References | Related Articles | Metrics

In view of the stress field distribution of glass indentation caused by the spherical support of tempered vacuum glass, the Hertzian indentation equation was modified by using contact mechanics, and the three-dimensional stress field equations were derived. At the same time, the stress intensity factor of fully developed conical crack was numerically solved. The numerical results show that all the principal stresses inside the contact area between the sphere and the glass are compressive. The principal stress σ₁ leads to the initiation of the crack, while the principal stress σ₂ forms the annular crack. The minimum principal stress is perpendicular to the glass surface, and then deviates from the contact edge, which forms the approximately parallel curves. And the maximum tensile stress is always perpendicular to these curves. Therefore, under the action of the maximum principal tensile stress, the crack follows the trajectory of the minimum principal stress. The stress intensity factor at the crack tip determines the fracture toughness. With the crack propagation, the stress intensity factor decreases. After a certain distance from the surface, the stress intensity factor reaches the critical value and the crack stops. The normalized stress intensity factor under different indentation loads is a set of curves with similar shapes.

Road Materials

Optimal Design and Road Performance of Waterborne Acrylic Heat Reflective Coating on Asphalt Pavement

SHEN Aiqin, KONG Tao, GUO Yinchuan, QIAN Yao, LI Peng

2021, 40(11):  3829-3836. 

Asbtract ( 69 )   PDF (5406KB) ( 50 )  

References | Related Articles | Metrics

In order to reduce the temperature of asphalt pavement and alleviate the urban heat island effect, a new type of environmentally friendly waterborne acrylic heat reflective coating was prepared by selecting waterborne acrylic emulsion as the base material. The best quality mixing ratio of the paint was determined through orthogonal experiments. The indoor cooling device was used to test the influence of the amount of paint and temperature on the cooling effect. The correlation of the cooling effect was analyzed, and the anti-skid performance and adhesion performance of the coating were evaluated. The results show that the best quality mixing ratio of the paint is: the solid content of waterborne acrylic emulsion is 47%, the content of rutile titanium dioxide is 14%, the content of quartz powder is 7%, and the content of hollow glass beads is 3% (all above is mass fraction). The cooling effect increases with the increase of the amount of brushing, but after reaching a certain level, the cooling effect tends to be stable. The recommended best dosage is 1.0 kg/m². The cooling effect of the coating increases with the increase of temperature, and the correlation between indoor and outdoor cooling effects is extremely strong. With the increase of the amount of brushing, the anti-slip performance continues to decrease. The addition of anti-slip particles can effectively improve the anti-skid performance, and has almost no effect on the cooling effect. The adhesion performance increases with the increase of the amount of brushing, and the adhesion performance of the specimen is stronger after polishing.

Influence of Blending Degree Between Aged and Virgin Asphalt on Performance of Hot Recycled Asphalt Mixture

HAO Peiwen, LI Hongxiang, CUI Yingxiang, XU Jinzhi

2021, 40(11):  3837-3846. 

Asbtract ( 106 )   PDF (2565KB) ( 61 )  

References | Related Articles | Metrics

The blending degree between aged and virgin asphalt has a significant influence on performance of asphalt mixture in hot recycling procedure. At present, the blending degree is not considered in the mix design of hot recycled asphalt mixture in China. In order to explore the influence of the blending degree on technical performance and composition design of hot recycled asphalt mixtures, the high temperature performance, low temperature performance, water stability and anti-reflection cracking performance of the mixture prepared by conventional mixing method and artificially simulated 100% blending with mass fraction of 20%, 30%, 40%, 50% recycled materials for waste asphalt pavement (RAP) were studied. On the basis of establishing the relationship between road performance difference and RAP content under two mixing methods, the boundary RAP content which needs to consider the blending degree was determined. The results show that with the increase of RAP content, the high temperature performance of the mixture is enhanced, while the low temperature performance, water stability and anti-reflection cracking performance are reduced. Compared with the conventional mixing, the low temperature performance, water stability and anti-reflection cracking performance of the mixture mixed with 100% blending between aged and virgin asphalt are better, but the high temperature performance is poor. The difference of high temperature performance, low temperature performance and water stability increases gradually with the increase of RAP content, while the difference of anti-reflection cracking performance do not change significantly. Taking the content corresponding to the average growth rate of performance difference as the boundary content, it is recommended that when the RAP content is more than 30%, the influence of the blending degree between aged and virgin asphalt should be considered in the design of hot recycled asphalt mixture.

Water Stability of Warm-Mix High Viscosity Asphalt Mixture Based on Dynamic Water Scour Test

HUANG Weirong, WANG Jiao, YANG Yuzhu, XIONG Kelin

2021, 40(11):  3847-3853. 

Asbtract ( 125 )   PDF (3267KB) ( 57 )  

References | Related Articles | Metrics

This article focused on the water stability of drained asphalt pavement. The water stability of high viscosity asphalt and warm-mix high viscosity asphalt mixtures were compared and analyzed through the immersion stability test, the Cantabro test and the freeze-thaw splitting test. A high-precision river dynamics flume test system was introduced in the research. A freeze-thaw cycle-dynamic water scour-splitting coupling test was designed to study the water stability of warm-mixed high viscosity asphalt mixtures. The mass loss rate and splitting strength ratio of three kinds of OGFC-13 high viscosity asphalt mixtures were studied under different scouring heights, scouring speeds and scouring time. The results show that the residual stability of high viscosity asphalt mixture exceeds 100%. The results of the dispersion loss of three kinds of asphalt mixtures are below 11%, and the freeze-thaw splitting strength ratio is above 95%. There is no significant difference among the test results, so the existing standard methods cannot effectively evaluate the water stability of the warm-mix high viscosity asphalt mixture. In the freeze-thaw cycle-dynamic water scour-splitting coupling test, the speed and time of scouring have the greatest impact on the water stability of the high viscosity asphalt mixture. The mass loss rate reaches 4% after 3 d of scouring and exceeds 5% after scouring at a speed of 30 L/s, and the splitting strength ratio drops below 85% at the same time. The water stability of the warm-mix high viscosity asphalt mixture can be evaluated by the freeze-thaw cycle-dynamic water scour-splitting coupling test.

Mechanical Properties of Fly Ash Reinforced Subgrade Soil in Seasonally Frozen Area

CHENG Zhuo, CUI Gaohang, GAO Yuanhao, GANG Haohang, GAO Zening, YANG Zheng, ZHANG Xin

2021, 40(11):  3854-3864. 

Asbtract ( 68 )   PDF (9037KB) ( 40 )  

References | Related Articles | Metrics

In order to investigate the influence of freeze-thaw cycle on the mechanical properties of subgrade soil reinforced with fly ash, unconfined compression test and triaxial shear test were carried out on saline soil with different freeze-thaw cycle times, moisture content and fly ash content. What's more, the changes of stress-strain curve, unconfined compressive strength, cohesion and internal friction angle of soil after freeze-thaw cycle were studied. Based on Design-Expert 8.0 software, the influence of freeze-thaw cycle times, fly ash content, moisture content and the interaction of various factors on the mechanical properties of saline soil was explored. The results show that the unconfined compressive strength, cohesion and internal friction angle of saline soil decrease after several freeze-thaw cycles, and the mechanical parameters of soil decrease rapidly after 1 to 7 freeze-thaw cycles. With the increase of fly ash content, the internal friction angle, cohesion, unconfined compressive strength and shear strength of saline soil increase at first and then decrease. Based on the theory of significance analysis, the interaction between freeze-thaw cycles and moisture content has a significant effect on the unconfined compressive strength and cohesion of saline soil. The interaction between fly ash content and freeze-thaw cycles only has obvious significance on unconfined compressive strength. In order to improve the strength and frost-thaw resistance of subgrade soil and speed up the comprehensive utilization of fly ash, it is recommended to add 15% fly ash to subgrade soil according to the mass ratio. The mechanical index of compacted saline soil after seven freeze-thaw cycles is taken as the reference value of engineering design.

Unconfined Compressive Strength and Environmental Impact Assessment of Industrial Waste Stabilized Roadbed Soil

ZHAO Weiqi, FANG Rui, ZHOU Hao, LI Na, JIANG Ping

2021, 40(11):  3865-3875. 

Asbtract ( 104 )   PDF (8630KB) ( 92 )  

References | Related Articles | Metrics

With the development of modern society, the scale of road engineering construction is becoming larger and larger, and the price of commonly used curing agents such as lime and cement is high. It is a good way to apply calcium carbide residue (CCR) and fly ash (FA) to road construction, which can not only improve the recycling rate of resources, but also reduce the construction cost. In this paper, the optimum mix proportion of CCR and FA in solidified soil was explored, and the feasibility of CCR replacing lime to solidify soil was discussed. In addition, adding polypropylene fiber into the CCR-FA solidified soil can further improve the mechanical properties of CCR-FA solidified soil, so would also be explored the optimal content of polypropylene fiber. The results of the unconfined compression test show that the optimal ratio of CCR and FA is 1:1, and the optimal content of polypropylene fiber is 0.6% (mass fraction). On this basis, the impact of CCR-FA solidified soil on the environment under rain conditions was investigated. The pH test results demonstrate that the maximum pH value of CCR-FA solidified soil is 12.28, which meets the requirements of national standards and can be applied in actual projects. The research results serve as a solid foundation in utilizing industrial waste as road base materials.