Table of Content

15 July 2021, Volume 40 Issue 7

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Cement and Concrete

Research Progress on Understanding Hydration Process and Its Mechanism of Cement Mineral System During Induction Period

GUAN Min, HU Kuangyi, YU Tao, CHU Jingyuan, AI Xiaojing, CHANG Zheng, GAI Linlin, SHENG Jiacheng

2021, 40(7):  2129-2137. 

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Cement hydration is a key process to determine properties such as rheological property, mechanical property, volume stability and durability of cementitious materials. The hydration process during induction period makes an important role on the property development of cementitious materials. Therefore, understanding the hydration mechanism of cement and clarifying the hydration process of main cement clinker monominerals such as tricalcium silicate (C₃S) system and tricalcium aluminate-gypsum (C₃A-CH₂) system during induction period would find out how to control the property development of cementitious materials in a better way. On this account, thermodynamic mechanism of cement hydration was reviewed. The hydration process and hydration mechanism of C₃S system and C₃A-CH₂ system during induction period were also discussed. However, limited to the current research methods, the interrelation and interaction of various monominerals systems in the induction period of cement are still not fully clarified, and further exploration is needed.

Effect of Zeolite Powder on Hydration Behavior of Calcium Sulfoaluminate Cement

GUI Ruoming, LIAO Yishun, HUANG Haoran

2021, 40(7):  2138-2144. 

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The effects of zeolite powder on fluidity, setting time and compressive strength of calcium sulfoaluminate cement pastes were studied, and the mechanism of zeolite powder in the hydration behavior of calcium sulfoaluminate cement was analyzed by autogenous shrinkage, electrical resistivity and XRD. The results show that the fluidity of the cement paste decreases obviously with the addition of zeolite powder, and the setting time increases significantly, and then increases slowly with the increase of zeolite powder. When the zeolite powder mass content is from 5% to 15%, the compressive strength of hardened cement paste at 1 d, 3 d and 7 d increases significantly. When the zeolite powder mass content is 10%, the compressive strength of cement paste at 3 d, 7 d and 28 d increases by 21.6%, 13.9% and 5.4%, respectively, compared with the control group. After adding zeolite powder, the electrical resistivity of cement paste at 24 h increases significantly, and the autogenous shrinkage of hardened cement paste decreases at 7 d. At the same age, the autogenous shrinkage of hardened cement paste decreases with the increase of zeolite powder. XRD analysis shows that the addition of zeolite powder effectively promotes the hydration of calcium sulfoaluminate cement, and is beneficial to the formation of ettringite at 1 d, 3 d and 28 d ages.

Effects of Curing Conditions on Hydration Behavior and Pore Structure of EVA Emulsion Modified Cement Paste

DING Shaopei, WANG Jiantao, LIU Yunpeng, HE Yongjia

2021, 40(7):  2145-2151. 

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In this paper, the polymer modified Portland cement paste with different EVA emulsion content was prepared. The hydration properties and pore structure of the modified Portland cement paste under the same water cement ratio and different curing systems (standard curing and steam curing) were compared. The effects of EVA emulsion on the hydration products, hydration characteristics, pore structure and compressive strength of the cement under different curing conditions were evaluated by X ray diffraction analysis, hydration heat analysis, mercury intrusion analysis, nitrogen adsorption test and cube compressive strength test. The results show that compared with the standard curing, EVA emulsion does not change the hydration products of cement under the steam curing. When the amount of EVA emulsion is higher, it decreases the degree of cement hydration, reduces the porosity of samples, increases the pore size of samples, and the steam curing decreases the negative effect of EVA emulsion on the strength of the cement paste.

Effect of Ca-LDH Modified by Sodium Lignosulfonate on Properties of Cement-Based Materials

CHEN Mengzhu, YU Linwen, YUAN Huihui, ZHENG Haibing, WU Fang, CAI Yuxin, LI Weihua

2021, 40(7):  2152-2158. 

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Layered double hydroxides (LDHs) are a new type of multifunctional two-dimensional nanomaterials. The hydration product (AFm phase) of cement belongs to the calcium-aluminum hydrotalcite series. Because of the excellent properties of LDHs, it has a broad application prospect in the field of building materials. Using sodium lignosulfonate as modifier, lignosulfonate modified LDHs (Ca-SLS-LDH) was synthesized by the hydrothermal synthesis method. The differences between the surface morphology, average particle size and specific surface area of Ca-LDH before and after modification were compared. The effects of different amounts of Ca-LDH on cement setting time, mortar fluidity and mechanical properties were studied, and the composition and microstructure of the cement hydration products were analyzed by SEM, XRD and mercury intrusion porosimetry (MIP). The results show that the average particle size of Ca-SLS-LDH is smaller, and the specific surface area is more than 60 times that of the unmodified Ca-LDH, when the content of LDHs does not exceed 4% (mass fraction), it can effectively improve the pore structure of the cement and promote the strength of the cement mortars, and the content of 6% (mass fraction) can cause the porosity to increase and the strength to decrease.

Influence of Graphene Oxide on Rheological Properties of Fresh Cement Paste

JIAO Min

2021, 40(7):  2159-2164. 

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With the continuous development of nano-materials and technology, more and more attention has been paid to the modification of cement-based materials by graphene oxide. In this context, the influence of graphene oxide on the rheological properties of fresh cement paste was studied by Anton Paar Rheolab QC rheometer, and the static yield stress, dynamic yield stress, viscosity coefficient and thixotropic ring area of the paste were measured. The results show that under the same content of graphene oxide, the longer the paste resting time is, the higher the static yield stress is. With the increase ofthe graphene oxide content, the paste microstructure establishment parameters, dynamic yield stress, and viscosity coefficient first increase and then decrease, while the thixotropic loop area shows an opposite changing trend.

Experimental and Numerical Studies on Fiber Pull-Out of Steel Fiber Reinforced Cement Mortar at Different Ages

ZHAO Nan, QING Longbang, YANG Zhuofan, MU Ru

2021, 40(7):  2165-2173. 

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As a kind of multiphase composite, the reinforcement and toughening effect of steel fiber reinforced cementitious composite depends on the interfacial bonding properties between steel fiber and matrix. According to the single fiber pull-out tests and numerical simulation of the steel fiber reinforced cement mortar at different ages, the effects of ages on the interfacial bond properties of steel fiber reinforced cement mortar were studied. A meso-scale model of single fiber pull-out tests of the steel fiber reinforced cement mortar at different ages was established and verified by comparison with the simulated and tested results. The mechanism of interfacial bond between fiber and matrix of steel fiber reinforced cement mortar at different ages and the stress variation of the section around the interface between steel fiber and cement mortar matrix were analyzed by this model. The results show that, the simulated peak pull-out load and the pull-out curves are in good agreement with the tested results. Both the peak pull-out load of steel fiber and the interfacial bond strength between steel fiber and cement mortar matrix increase with the increase of age. The interfacial bond strength increases rapidly in the stage of the first 7 d, then slows down. The growth rate of interfacial bond strength in different age periods gradually decreases and tends to be stable with the increase of ages. The fitted mechanical parameters of the interface between steel fiber and cement mortar effectively simulate the pull-out process of the steel fiber.

PP/PVA Fiber Reinforced Sulphoaluminate Cement-Based Rapid Repair Material

ZHANG Chenglong, LIU Yi, ZHANG Ming

2021, 40(7):  2174-2183. 

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With the increase of traffic pressure, the road surface of highways and bridges is prone to fatigue failure. In this paper, polypropylene (PP) fiber and polyvinyl alcohol (PVA) fiber are used to improve the properties of sulphoaluminate cement-based rapid repair material. The effects of single and compound PP and PVA fibers on fluidity, strength and toughness of sulphoaluminate cement-based rapid repair materials were investigated, and the effects of the optimal mixing ratio on the bonding strength and volume stability of the repair materials were also studied. The results show that the single PP fiber has little effect on the fluidity of mortar, and significantly improves the flexural strength. After adding 0.2% (volume fraction, the same below) PP fiber, the fluidity only decreases by 4%, and the 1 d and 28 d flexural strengths reach 12.8 MPa and 15.5 MPa, respectively. The single addition of PVA fiber significantly reduces the fluidity of mortar repair materials and enhances the compressive strength. The fluidity of mortar decreases by 21% with the addition of 0.2% PVA fiber, and the 1 d and 28 d compressive strength reach 56.6 MPa and 84.3 MPa, respectively. When the ratio of PP and PVA fibers is 3:1 and the total volume content is 0.2%, the two kinds of fibers play a synergistic role to make the quick repair material not only obtains good flow performance, strength, and toughness, but also improves the bonding performance and shrinkage characteristics of mortar. At 28 d, the mortar bonding strength reaches 5.6 MPa, and the drying shrinkage rate is 2.73×10^-4, which better meets the rapid repair needs of highways and bridges pavement and expansion joints.

Capillary Transport Kinetics of Epoxy Resin Repairing Discrete Microcracks in Cement-Based Materials

WANG Xingang, LI Yujie, ZHOU Zhen

2021, 40(7):  2184-2190. 

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To investigative the dynamic capillary transport process of self-healing microcapsule core material (epoxy resin) to repair microcracks in cement-based materials, contact angle and surface tension of epoxy resin were measured by optical contact angle measuring instrument, and dynamic viscosity of epoxy resin was measured by automatic heating rotary rheometer. The modified Lucas-Washburn equation (L-W equation) was used to analyze the influence of microcracks width and epoxy resin’s gravity on the dynamic capillary transport process. The results show as follows, the capillary transmission speed of epoxy resin in microcracks is faster at first and then slower, and the capillary transmission speed is related to the width of cracks. The effect of the repair agent gravity cannot be ignored in dynamic capillary transport process. When the microcrack width is 0.05 mm, the dynamic capillary transmission process is predicted accurately by the modified L-W equation, and the deviation is within 0.9%. When the microcrack width is 0.10 mm, the deviation between the theoretical value and experimental value is only 11.9%.

Axial Compression Performance of Rubberized Concrete-Filled Steel Tube Short Columns

XING Haoran, MAO Niandong, YANG Xinran, ZHOU Zhi, HUANG Wei

2021, 40(7):  2191-2199. 

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In order to solve the limitation of engineering application of rubberized concrete caused by its lower strength and elastic modulus, 12 rubberized concrete-filled steel tube (RuCFST) columns, in which waste tire rubber was used to replace fine aggregate by the same volume, were fabricated and tested under axial compression in this paper. The test results show that the steel tube of RuCFST columns is more prone to local buckling and RuCFST columns exhibit lower axial compressive capacity and higher ductility than normal CFST columns. RuCFST columns demonstrate hardening post-peak response, compared with normal CFST columns with the same steel tube thickness. Finally, the axial compressive capacity of RuCFST columns was investigated by AISC 360—2005, Eurocode 4 and GB 50936—2014 codes. The results show that the predictions of the axial compressive capacity of RuCFST columns by AISC 360—2005 and GB 50936—2014 are conservation and Eurocode 4 provides the most accurate results compared with the test results.

Axial Compressive Performance of Concrete Column Reinforced by Prestressed Steel Strips

ZHANG Bo, YANG Yong, XIA Zeyu

2021, 40(7):  2200-2208. 

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Thirty-two reinforced columns and four unreinforced columns were tested under axial compression. The effects of the steel strip spacing and layer number on the bearing capacity and deformation capacity were investigated. Experimental results show that the cylindrical concrete column specimens with prestressed steel strips can effectively improve the axial compression performance. Not only the bearing capacity of columns under axial compression is improved, but also the deformation capacity is improved as well. Based on the experimental results, the mechanism of the concrete column with prestressed steel strip was discussed. The ultimate strength model of the cylinder concrete column with prestressed steel strips under axial compression was proposed, and the calculated value is in good agreement with the experimental value.

Influence of Surface Coating on Water Absorption Performance of Concrete

LIU Fang, XIONG Rui, ZHONG Yongqiang

2021, 40(7):  2209-2214. 

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Four kinds of surface coatings were used, and the water absorption rate was used as an evaluation index to study the change law of water absorption performance of the concrete specimens after the surface coating. The test results show that the surface coatings reduce the water absorption rate of the concrete specimens to varying degrees. The effect of polyurethane coating is the best, and the effect of emulsion coating is the worst. The effects of fluorocarbon coating and bridge coating are between the polyurethane coating and the emulsion coating. With the increase of times of coating brushing, the water absorption rate of the concrete specimens gradually decreases, but the reduction range decreases. According to the environment of the concrete structure, select the appropriate times of coating brushing from the economic point. With the increase of water-cement ratio, the water absorption rate of the blank and the painted concrete specimens increases significantly.

Cause Analysis of Freeze-Thaw Erosion of Pervious Concrete

XIANG Junzheng, SONG Hui, LENG Menghui, GUI Faliang

2021, 40(7):  2215-2224. 

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In order to explore whether the freeze-thaw erosion of the pervious concrete comes from the deterioration of cement paste, the aggregate of 2.5 mm to 10.0 mm was selected to prepare the pervious concrete with 0.31 water-cement ratio and the cement paste with the same water-cement ratio. The changes of mass, strength of the cement paste and the pervious concrete, and the relative dynamic elastic modulus of the pervious concrete under freeze-thaw cycles were measured. The characteristic parameters of pore structure and the pore size distribution of the cement paste under freeze-thaw cycles were measured by mercury porosimetry (MIP). The evolution of aggregate and cement paste interface morphology of the pervious concrete was observed by SEM. The results show that the macro performance indexes of the pervious concrete decrease in different degrees in water freezing and salt freezing environment, and cracks appear at the interface of aggregate and cement paste, and expand with the increase of freeze-thaw times. However, the strength, quality and micro pore structure of the cement paste have no obvious changes. This indicates that the freeze-thaw deterioration of the pervious concrete is related to the interface between aggregate and cement paste.

Solid Waste and Eco-Materials

Damage Model of Desert Sand Fiber Reinforced Concrete under Freeze-Thaw Cycles

ZHANG Guangtai, GENG Tianjiao, LU Haibo, WANG Mingyang, LI Xuefan

2021, 40(7):  2225-2231. 

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In order to study the damage model of desert sand fiber reinforced concrete under freeze-thaw cycles, the rapid freeze-thaw tests of 0 times, 25 times, 50 times, 75 times, 100 times, 125 times and 150 times were carried out on desert sand fiber concrete. The attenuation law of relative dynamic elastic modulus, compressive strength and splitting tensile strength of desert sand fiber concrete after different freeze-thaw cycles were analyzed. Combined with test data, the freeze-thaw damage deterioration model of desert sand fiber concrete was established based on exponential function and quadratic function. The results show that compared with desert sand concrete, the freeze-thaw resistance of desert sand concrete with polypropylene fiber is effectively improved. With the increase of freeze-thaw cycles, the relative dynamic elastic modulus decreases continuously. After 150 freeze-thaw cycles, the compressive strength and splitting tensile strength of desert sand fiber concrete decrease by 49.5% and 70.13% respectively compared with 0 times freeze-thaw cycle. Two damage models of desert sand fiber concrete under freeze-thaw environment are established, and the calculated values are in good agreement with experimental values, which can provide a theoretical reference for the application of desert sand fiber concrete in severe cold areas.

Effect of pH Value on Static Uniaxial Mechanical Properties of Sandstone under Dry-Wet Cycle

YUAN Pu, BU He, WEI Ningning

2021, 40(7):  2232-2239. 

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In order to study the effect of dry-wet cycles of solutions with different pH values on the deterioration of mechanical properties of sandstone, four solutions with pH values of 3, 5, 6.5 (distilled water) and 7 were used to perform dry-wet cycles on sandstone. Sandstone specimens with 0 times (dry state), 1 times, 10 times and 20 times of dry-wet cycles were subjected to longitudinal wave velocity measurement, water absorption test, XRD test and uniaxial compression test. Test results show that under the same pH value of the solution, the uniaxial compressive strength of sandstone specimens decreases gradually with the increase of dry-wet cycles. When the number of dry-wet cycles is the same, as the pH value of solution decreases, longitudinal wave velocity of sandstone specimens decreases, water absorption gradually increases, the internal mineral composition changes, and uniaxial compressive strength gradually decreases and tends to be stable. The deterioration of sandstone specimens under dry-wet cycles of acidic solution are more serious than that of neutral solution, and the lower the pH value is, the greater the deterioration is.

Mixture Ratio Design and Application of Chemically Improved Lake Peat Soil

RUAN Yongfen, YANG Bing, WU Long, LIU Kewen, ZHU Qiang

2021, 40(7):  2240-2247. 

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In order to meet the needs of the project, the lake peat soil was improved by chemical reinforcement. For the lake peat soil in 3 sites, 11 kinds of additives such as water reducing agent, early strength agent, auxiliary cementing material were added, 23 kinds of ratio improvement schemes were formulated, and the indoor unconfined compressive strength and light cone dynamic penetration test were adopted. Then the best ratio of the chemical curing agent was obtained. The experimental results show that the compressive strength of the soil mixed with the modifier is larger than that of the original soil, and it increases with the increase of the age. The best ratio and content (mass fraction) are 25% cement, 6% quicklime, and 1% fly ash, and the water-cement ratio is 1:1.

Solidification of Marine Soft Soil under Alkali Excitation

WANG Weiqi, SUN Hong, GE Xiurun

2021, 40(7):  2248-2255. 

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In order to improve the effect of industrial waste calcium carbide slag and undisturbed ash on the solidification of soft soil, polycarboxylate superplasticizer, sodium silicate, sodium sulfate, and triethanolamine were selected as additives. The unconfined compressive strength test (UCS), X-ray diffraction (XRD), and scanning electron microscope (SEM) were used to study the synergistic effect of the additives. The results show that 0.1% (mass fraction) polycarboxylate superplasticizer combined with 3% (mass fraction) sodium silicate or 0.9% (mass fraction) sodium sulfate can significantly improve the strength of solidified soil, and the composite early strength agent with 1:1 ratio of sodium silicate and sodium sulfate was determined. The optimum ratio of superplasticizer, composite early strength agent and industrial waste residue were determined by orthogonal test. At the age of 7 d and 28 d, the strength increase of the solidified soft soil with composite early strength agent is 47% and 77% higher than that without composite early strength agent. At the age of 7 d, the dispersion effect of superplasticizer plays a leading role in the solidified soil, while at the age of 28 d, the pozzolanic effect of composite early strength agent under alkali excitation is more obvious.

Pulping Properties and Mechanism of Bentonite Controlled by Polymer

LI Xin, WU Xuelan, LONG Hongming, WANG Weikui, YU Zhengwei, LI Xiang

2021, 40(7):  2256-2263. 

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Based on the test of sodium bentonite with 43% montmorillonite content in Jiangsu province, it was found that the Φ600 of mud was 5 mPa·s, and the filter loss was 27 mL. The bentonite cannot meet the requirements of national standard soil. In this paper, a scheme was proposed to improve the pulping performance by adding different polymers. The influence of polymer on the properties of bentonite slurry was studied by single factor experiment. SEM,FTIR, XRD and Zeta potential were used to investigate the mechanism of the effect of the polymer on the slurry-making properties of bentonite. The optimum polymer composition and dosage were obtained by orthogonal experiment and optimization experiment. The results show that the polymer is adsorbed on the surface of bentonite particles, which is not only beneficial to the formation of hydrogen bond on the crystal surface, but also to the formation of network structure. Which improves the viscosity of the mud, and reduces the loss of mud. When the polymer is 0.1% (mass fraction) sodium polyacrylate+0.4% (mass fraction) carboxymethyl starch, the Φ600 of mud is 60.5 mPa·s, and the filter loss is 14.5 mL. Other properties also met the requirements of the national standard for mud soil.

Study on Reinforcement of Diatomite/Silica Composite Filler

ZHANG Zhaohong, LI Peipei, XING Lihua, WANG Zaixue, GOU Jialong, XU Yunhui

2021, 40(7):  2264-2269. 

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In order to expand the application of diatomite in polymer composites, the composite material was prepared by diatomite/silica composite filler into natural rubber/styrene butadiene rubber/butadiene rubber (NR/SBR/BR). The Payne effect and dispersion of the composite fillers were analyzed by RPA2000 and SEM. The effects of diatomite content on the technological properties, mechanical properties, and wear resistance of the composites were investigated. The results show that the addition of a small amount of diatomite is beneficial to the dispersion of silica in rubber, reduce the Mooney viscosity and Payne effect of the composite material, improve the curing speed and shorten the curing time, and thecomposite filler has better reinforcement effect. The composite filler is easy to aggregate and the mechanical properties of the composites are decreased, the wear properties are changed little when the amount of diatomite is increased. The composite material has the best comprehensive performance when the diatomite dosage is 10~20 phr.

Composition Design and Erosion Wear Analysis of Al-B₂O₃-CeO₂-Fly Ash Composite Reinforced Coating

SUN Fanghong, MA Zhuang, SUN Guodong, GAO Zhiyu

2021, 40(7):  2270-2279. 

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In order to improve the application and performance of fly ash reinforced materials in metal matrix composites, thermodynamic analysis, and orthogonal optimization experiments are used to determine the possible reactions between the components of the Al-B₂O₃-CeO₂-fly ash composite reinforced coating and the best ratio formula. At the same time, the fly ash composite reinforced coating was prepared on ZG310-570 matrix by plasma spraying. The surface morphology, phase, and erosion wear properties of the fly ash composite reinforced coating were also analyzed. Thermodynamic analysis and orthogonal optimization experiments show that solid-phase reactions occur between Al, B₂O₃, CeO₂ and fly ash. The best proportion of fly ash composite reinforced coating formula was fly ash 55%, B₂O₃20%, Al20%, CeO₂5% (mass fraction). The fly ash composite reinforced coating has an uneven lamellar structure with good compactness, but there are longitudinal cracks, insufficiently melted particles, and pores. The results of X-ray analysis and thermodynamic analysis show that the fly ash composite reinforced coating has new phases such as Al₂O₃, CeB₆, 2MgO·SiO₂, 3CaO·B₂O₃, etc. In a certain erosion time, erosion angle and different erosion speeds, the relative erosion resistance of the fly ash composite reinforced coating was at least 20.41 times, 22.43 times and 23.17 times higher than that of the ZG310-570 matrix, respectively.

Physicochemical and Thermal Activation Properties of Waste Coal Gangue in Pingxiang Mining Area

YAO Suqin, ZHA Wenhua, LIU Xinquan, JI Shengxing, HE Changchun, YU Yue

2021, 40(7):  2280-2287. 

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In order to study the physicochemical properties of different types of coal gangue and the influence of calcination temperature on its activation degree, sample A, sample B and sample C from different mining areas of discarded coal gangue in Pingxiang were taken as the research objects. Based on the XRD test, physical property test, high temperature test and mechanical property test, the basic properties and thermal activation properties of coal gangue were analyzed from the aspects of physical and chemical characteristics, mechanical characteristics, and apparent characteristics. The results show that the physical and chemical properties of different types of gangue are different, and the gangue with higher active substance content has higher activity. Compared with sample A, sample B and sample C are more suitable for packing, and sample Chas higher porosity, water absorption and resistance to natural weathering and cracking. The optimal calcination temperature of different types of gangue varies slightly, all of them are about 800 ℃. The coal gangue which is not calcined or does not reach the optimal calcination temperature has low activity, and the prepared specimen has poor cementation and low strength. The coal gangue at the calcination optimum temperature has the highest activity, the best cementation, and the highest strength.

Water Resistance of Flue Gas Desulfurization Building Gypsum Modified by Ordinary Portland Cement

GUO Huishi, WANG Qingpei, ZHANG Guo, LI Wenfeng, MENG Erchao, CHEN Wenliang, HUI Shouhua, ZHOU Liming

2021, 40(7):  2288-2295. 

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The gypsum has been limited in building field due to its poor water resistance. The modified flue gas desulfurization (FGD) building gypsum with well water resistance and low cost was fabricated with the FGD building gypsum and ordinary Portland cement as raw materials in this paper. The effect of cement content on physical properties, phase composition, and microstructure of hydrated samples was systematically investigated. Results show that with the increase of the ordinary Portland cement content, the content of AFt, CH, and C-S-H increases, which fill the pores, so that the water absorption decreases first and then increases, while the softening coefficient, contact angle, and hardness show an opposite trend. When the content of cement is 18% (mass fraction), the hydrated sample shows a well water resistance. This study provides a technical basis for the preparation of the FGD building gypsum and its products with well water resistance, low-cost, and environment-friendly, which also has an important significance to the popularization and application of the FGD gypsum.

Effects of High Performance Mineral Admixtures on Performance of High Strength Manufactured-Sand Concrete

DUAN Chenggang, SUN Yongtao

2021, 40(7):  2296-2305. 

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To analyze the influence law of S105 mineral powder and other mineral admixtures on workability, compressive strength, and drying shrinkage of C80 high strength manufactured-sand concrete quantitatively, the slump, expansion, compressive strength, and drying shrinkage of high strength manufactured-sand concrete at different ages (3 d, 7 d, 28 d, 60 d) were measured. The raw material in the experiment was the mixture of concrete raw material and S105 mineral powder, or the mixture of concrete raw material, S105 mineral powder and mineral admixtures. In the second case, the cement was replaced by microspheres, ultrafine mineral powder or micro-silica with different dosages, respectively. Then, the variation trend of the performance of high strength manufactured-sand concrete was analyzed by the corresponding charts and the actual state of concrete mixture. The result shows that the workability and compressive strength of high strength manufactured-sand concrete are improved, and the drying shrinkage is reduced significantly by adding mineral admixtures in a certain dosage range. Compared with the single mixing of S105 mineral powder, the mixing of S105 mineral powder and different mineral admixtures significantly improve the comprehensive performance of concrete. Meanwhile, the concrete maintains good workability. Considering the influence of workability, strength, and drying shrinkage, when the cement mass dosage replaced by ultrafine mineral powder is 3%, that is, the mass ratio of cement, S105 mineral powder, and ultrafine mineral powder is 33:11:1, the performance of high strength manufactured-sand concrete is at a good level. In this case, the cohesion and fluidity of concrete are significantly improved, the 3 d and 60 d compressive strength increases by 3.1% and 5.1%, respectively, and the drying shrinkage rate decreases by 4.0%.

Dynamic Characteristics and Microscopic Mechanism of Muddy Clay Solidified by Ground Granulated Blast-Furnace Slag

QIAO Jingsheng, WANG Xuying, WANG Guanhong, ZHAO Jianye

2021, 40(7):  2306-2312. 

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Different content of ground granulated blast-furnace slag (GGBS) was used to solidify the muddy clay. The dynamic triaxial test was used to determine the optimal amount of GGBS, and the dynamic strength, dynamic elastic modulus, and dynamic damping ratio of the solidified clay with the optimal amount of GGBS under different confining pressures were analyzed. Finally, SEM test and XRD test were used to analyze the microstructure and composition changes of GGBS solidified clay, and its solidification mechanism was revealed. The results show that when the mixing amount of GGBS is 20% (mass fraction, the same bellow), the dynamic strength of GGBS solidified clay increases stepwise, and 20% is the optimal mixing amount of GGBS. The dynamic strength of 20% GGBS solidified clay is 2 times to 4 times that of the muddy clay, increasing by 45 kPa to 60 kPa, and the maximum dynamic elastic modulus is 3 times to 4 times that of the muddy clay, and the dynamic damping ratio is relatively reduced. Especially under the confining pressure of 100 kPa and 150 kPa, the dynamic damping ratio decreases significantly. The SEM images show that the solidified soil particles with 20% GGBS become agglomerated, the pores between the particles are greatly reduced, and the soil becomes relatively dense. The EDS patterns show that a large amount of Ca²⁺ undergoes ion exchange and granulation, thereby enhancing the binding force between soil particles. The internal friction angle of the clay particles becomes larger, and the strength of the clay body is also improved.

Immobilization and Kinetics of Mn²⁺ in Electrolytic Manganese Residue

FENG Shengxia, YANG Min, ZHANG Yu, DUAN Jiangfei, HE Weilong, LI Rui

2021, 40(7):  2313-2319. 

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The soluble manganese in electrolytic manganese residue (EMR) leads to serious environmental problems, and it’s important to solidify the soluble manganese. In this article, the immobilization of Mn²⁺ in EMR curing by CaO and its kinetic mechanism were studied. The effects of the content of CaO, liquid-solid ratio, temperature and reaction time on the Mn²⁺precipitation efficiency were investigated systematically. The structure and morphology of raw EMR and treated EMR were characterized by XRD and SEM-EDS. The results show that with the CaO:EMR mass ratio of 6:100, liquid:solid ratio of 4:1, temperature of 55 ℃, and reacting time of 150 min, the Mn²⁺ precipitation efficiency is 99.72%. The mechanism demonstrated that Mn²⁺ is immobilized in the form of groutite (MnOOH) and ramsdellite (MnO₂). The results of kinetics show that it is controlled by the chemical reaction and diffusion mixing of the residual solid film, and the apparent activation energy of the reaction is 11.713 5 kJ/mol. This study provides a simple and effective method to modify manganese residue, which can be applied to guide the sustainable utilization of manganese residue.

Heat Resistance and Thermal Damage Law of Blast Furnace Nickel-Iron Slag and Steel Fiber Modified Concrete

LIU Yaqi, WANG Shujuan, LI Lixin

2021, 40(7):  2320-2330. 

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The concrete was modified with blast furnace nickel-iron slag and steel fiber, and then the mechanical properties and thermal damage law of the modified concrete after thermal cycling were studied through strength test and ultrasonic speed test. The strength test shows that thermal cycling has an accumulative effect on the strength degradation of the modified concrete. An appropriate amount of blast furnace nickel-iron slag and steel fiber improve the heat resistance of the concrete, but too much steel fiber will reduce the heat resistance of the concrete. The optimal amount of fiber is 0.5% (volume fraction) to 1.0%. The ultrasonic speed test shows that the ultrasonic speed in the concrete decreases continuously with the increase of the number of thermal cycles, similar to change law of compressive and tensile strength. According to the results of ultrasonic speed test and strength test, the relationship between ultrasonic speed and strength is established, and a generalized damage factor expression is established. Compared with the damage factors of different parameters, the results shows that the sensitivity of each parameter to thermal cycling is: wave velocity>tensile strength>compressive strength; the improvement effect on thermal cycling damage is: steel fiber>blast furnace nickel-iron slag; low water-cement ratio>high water-cement ratio.

Experimental Study on Basic Mechanical Properties of Recycled Tyre Steel Fiber Recycled Aggregate Concrete

FAN Xiaochun, ZHANG Wenjing, LIANG Tianfu, CHEN Kaifeng

2021, 40(7):  2331-2340. 

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The basic mechanical properties and damage modes of concrete are important indicators of the load-bearing capacity and toughness of the specimens under different stress conditions. To investigate the basic mechanical properties of recycled tyre steel fiber (RTSF) recycled aggregate concrete, 8 sets of concrete specimens of different types were designed for the test. The effects of RTSF volume fraction (0.25%, 0.5%, 0.75% and 1.0%) and recycled aggregate replacement rate(the mass fractions are 50%, 75% and 100%, respectively) on the basic mechanical properties and failure modes of concrete were systematically investigated by slump, gas content, cubic compressive, splitting tensile and flexural tests. The results show that with the increase of recycled aggregate replacement rate, the slump of concrete mixture decrease and the gas content increase, and the mechanical properties are reduced to different degrees. RTSF effectively improves the basic mechanical properties of recycled aggregate concrete, and the failure mode of the specimens shows obvious ductile damage characteristics with the increase of RTSF content. Comprehensive indicators, when the replacement rate of recycled aggregate is 50%, the mechanical properties of RTSF recycled aggregate concrete with RTSF volume content of 0.5% is the best. The cube compressive strength (28 d) of the specimens is only 1.0% lower than that of plain concrete, while the splitting tensile strength and flexural strength are 9.6% and 12.5% higher than that of plain concrete, respectively. In addition, the flexural toughness index I₅, I₁₀ and I₂₀ of the concrete are 2.7 times, 3.8 times and 4.8 times of that of the plain concrete, respectively.

Effects of Different Types of Recycled Fine Aggregate on Mechanical Properties of Thermal Insulation Concrete

HUANG Kailin, LI Shujin, ZANG Xuhang

2021, 40(7):  2341-2347. 

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In order to study the influence of different types of recycled fine aggregate on the mechanical properties of glazed hollow bead thermal insulation concrete, the natural river sand in thermal insulation concrete were replaced by recycled fine aggregate of waste concrete and recycled fine aggregate of clay brick at 25%, 50%, 75% and 100% (volume fraction) replacement ratio, respectively. And the recycled aggregate thermal insulation concrete compressive strength, splitting tensile strength and modulus of elasticity were measured. The experimental results show that 25% is the optimal replacement rate of recycled fine aggregate of waste concrete in thermal insulation concrete.75% is the optimal substitution rate of recycled fine aggregate of waste clay brick in thermal insulation concrete. Crushing value of recycled fine aggregate and strength ratio of recycled mortar effectively distinguish the quality of different types of recycled fine aggregate in practical engineering. The volcanic ash material in the recycled fine aggregate of the waste clay brick effectively improves the compactness of the recycled aggregate thermal insulation concrete, while the residual calcium hydroxide in the recycled fine aggregate of the waste concrete reduces the mechanical properties of the recycled aggregate thermal insulation concrete, so the recycled fine aggregate of the waste clay brick has higher recycling value.

Ceramics

Research Progress on Preparation of Biomimetic Materials by Freeze Casting under Magnetic Field

ALATENG Shaga, CHEN Guanhong, CHEN Xing

2021, 40(7):  2348-2359. 

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With the rapid development of science and technology, higher requirements are put forward for the performance of materials. It is urgent to develop new lightweight and high-performance structural materials, which have the characteristics of low density, high stiffness, high strength, and high toughness. After hundreds of millions years of evolution, biomaterials have formed fine and complex structures that are compatible with the environment and functional requirements, such as the “brick-mortar” structure of nacre and the helical structure of crab cuticle. They all exhibit extraordinary mechanical properties and unique functional characteristics, which greatly inspired the design and construction of high-performance materials. The currently developed freeze casting method (ice template method) is an effective method for preparing biomimetic materials. Usually, the water-based ceramics slurry is directionally solidified under the effect of temperature gradient. After freeze-drying, the porous ceramics with fine structure can be obtained. Then, the porous ceramics can be filled with soft phase resin to obtain the ceramics-resin composite with nacre-like structure. In order to further control the microstructure of the material, the researchers applied magnetic field to the freeze casting process, and finally found that the structure and properties of the material have changed significantly. In this paper, the progress in the control of material microstructure and the preparation of biomimetic materials by freeze casting are introduced, and the influence of magnetic field on freeze casting is summarized. The change of microstructure and mechanicalproperties of ice-templating materials assisted by magnetic field is summarized.

Research Progress on Synthesis of γ-AlON Ceramic Powders

LI Ke, YANG Zhangfu, LI Xinzhu, ZHU Chaodong, XIAO Meihui, ZHANG Junjie, BU Guoxiu

2021, 40(7):  2360-2367. 

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Transparent γ-AlON ceramics have the advantages of high hardness, good chemical resistance and high optical transmittance, and have extensive application prospects in national defense and commercial fields. Whereas, high-purity single-phase γ-AlON powders with less agglomeration, uniform distribution of particle size are critical in sintering highly transparent γ-AlON ceramics. In this paper, Al₂O₃-AlN phase diagrams and thermodynamic calculation results of γ-AlON are briefly introduced. And then, the research progress of γ-AlON powders synthesized by high temperature solid-state reaction, aluminothermic reduction nitridation, and carbothermal reduction nitridation, respectively, is reviewed. Finally, the future synthesis technologies for γ-AlON powder with <100 nm size are proposed.

Glass

Effect of Chemical Composition of Ge_xAs₂₀Se_80-x Glass on Structure and Physical Properties

XU Siwei, YANG Xiaoning, SHEN Xiang

2021, 40(7):  2368-2373. 

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In this paper, a series of Ge_xAs₂₀Se_80-x chalcogenide glasses were prepared to study the influences of chemical composition and mean coordination number on its structure and physical properties. The refractive index was measured by the prism coupling method. The transmission was measured by visible-near infrared spectrophotometer. Optical bandgap was derived through the transmission spectrum. The results show that the refractive index decreases and the optical bandgap increases with increasing Ge content up to a transition point corresponding to chemically stoichiometric composition. Raman spectra were measured and decomposed into different structural units. It is found that the relative number of heteropolar bonds in the glasses changes in a reasonable manner with chemical composition, and the number of homopolar bonds is closely related to the change of the bandgap and the refractive index. The main reason is that the band-tails formed by homopolar bonds reduce the optical bandgap. On the other hand, since the number of the structural units and physical properties of the glasses exhibit transitions at the glass with the chemically stoichiometric composition, it can be concluded that the chemical composition dominates physical properties of Ge_xAs₂₀Se_80-x chalcogenide glasses.

New Functional Materials

Study and Application on Modification of Bismuth Oxyhalide Photocatalyst

ZHANG Jingwen, LI Yinghua

2021, 40(7):  2374-2379. 

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Energy and environment, as two hot issues in the world today, have attracted people’s attention.To solve these two problems, photocatalytic technology has been favored by researchers.Among them, bismuth oxyhalide (BiOX, X=Cl, Br, I) stands out in the field of photocatalysis because of its special layered structure, suitable band gap width, and excellent photoelectric properties. Based on the structure and properties of bismuth oxyhalide, research on its modification is introduced. By means of morphology control, semiconductor compounding, ion doping and surface modification, the active site exposure, transmission and separation efficiency of photo-generated carriers and light absorption performance of bismuth oxyhalide and its composites are improved. At the same time, the applications of modified bismuth oxyhalide in the fields of energy and environment are listed, and the limitations of different modification methods are discussed, in order to provide a reference for the application of bismuth oxyhalide.

Preparation and Performance of WO₃ with Long Visible Light Absorption by One-Step Oxygen Enriched Calcination Method for Water Oxidation

LI Dong, LI Rui, WU Fachao, GAO Caiyun

2021, 40(7):  2380-2387. 

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Tungsten trioxide (WO₃) only responds to sunlight below 460 nm, which greatly limits its utilization for sunlight. Therefore, the current research is focusing on broadening the spectral response range of WO₃. In this paper, nitrogen intercalated WO₃ (N₂-WO₃) with wide spectrum visible light response was prepared by one-step oxygen enriched calcination method using ammonium paratungstate [(NH₄)₁₀H₂W₁₂O₄₂·xH₂O] as precursor. The effects of N₂ insertion on the structure and properties of WO₃ were investigated by XRD, SEM, EDS, UV-Vis DRS and Raman. The results show that N₂ insertion effectively narrows the band gap (2.25 eV) of N₂-WO₃, which is 0.51 eV less than that of pure WO₃ (2.76 eV); the N content has a significant effect on the visible light absorption capacity of N₂-WO₃, and the N content decreases with the increase of calcination temperature. The measurement results of incident photon current conversion efficiency (IPCE) show that N₂-WO₃ responds to visible light below 520 nm. The results of photocatalytic oxygen evolution show that the photocatalytic activity of N₂-WO₃ is better than that of pure WO₃.

Preparation and Pervaporation Performance of High Flux Silica Composite Membranes

LIU Xiaoyu, WU Hongdan, ZHOU Zhihui, LI Shengli, DENG Sihao

2021, 40(7):  2388-2395. 

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The acid resistance and stability exhibited by silicon composite membranes hold great promise for applications in the field of pervaporation. The support layer of the silica composite membranes were prepared by a vacuum suction dipping method to obtain a high flux silica composite membrane. In this paper, the optimal conditions for vacuum suction of the support layer were explored, and the surface and cross-sectional topography of the membranes were characterized by scanning electron microscope. The results show that when the mass concentration of the supporting layer sol is 2%, the vacuum suction time is 10 s, and the vacuum suction pressure is 0.10 MPa, dense silica composite membranes are prepared with the membrane thickness around 6 μm to 7 μm. The silica composite membranes prepared in this paper are applied to the pervaporation of isopropanol aqueous solution and show excellent separation performance, and the permeation flux of isopropanol is 6.42 kg/(m²·h).

Growth Evolution of Silicon Nitride Film over Time and Its Characteristics

SUN Jiaxin, ZHOU Bingqing

2021, 40(7):  2396-2400. 

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Silicon nitride (SiN_x) films have been widely used in optoelectronic devices due to their high dielectric constant and good stability, but the thickness of silicon nitride films has an important effect on the performance of devices. In order to solve this problem,silicon nitride films have been grown by plasma enhanced chemical vapor deposition (PECVD) at 13.56 MHz on glass and N-type monocrystalline silicon substrate using high purity NH₃, N₂and SiH₄ as reactant gas sources by optimizing other deposition parameters and changing deposition time. The samples were characterized by X-ray diffraction (XRD), ultraviolet-visible(UV-VIS) light transmittance spectra, fourier transform infrared absorption spectroscopy (FTIR) and scanning electron microscope (SEM). The relationship between deposition time and film thickness and the effect of deposition time on film properties were studied in detail. The results show that the prepared samples are amorphous SiN_x thin film structure and the crystallization is independent of deposition time. The thickness of the thin film increases uniformly with deposition time, the refractive index of the thin film increases with deposition time, and the optical band gap does not change with deposition time. SEM test results show that with the increase of deposition time, the film density and uniformity become better and better. Fourier transform infrared spectra show that the silicon/nitrogen ratio of the thin film does not change with deposition time, but the oxygen content decreases, indicating that the increased film density effectively prevents O atoms from entering the film and prevents the occurrence of oxidation after the thin film is deposited. The experimental results show that good optical properties and dense structure of silicon nitride films can be obtained by changing deposition time.

High Temperature Absorbing Properties of High Temperature Resistance Absorbing Coatingwith Frequency Selective Surface

YU Mingfei, YAO Lunbiao, QING Yuchang, QUAN Jingmin

2021, 40(7):  2401-2408. 

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Due to its adjustable surface impedance, the high-temperature-resistant resistance material has some excellent properties such as co-reflection, loss characteristics, and broadband. The frequency selective surface absorbing coatings were prepared by brush coating method in this paper. The composition, microstructure of the coatings, and high temperature stability of the square resistance were characterized by SEM and square resistance tester. The effects of coating heat treatment temperature and holding time on the reflectivity of absorbing materials were also studied by vector network analyzer. The results show that, after long time heat treatment at 600 ℃, the surface morphology of the ceramic coating has little change, the surface square resistance is stable, and the high temperature resistance is good. Such results suggest that the frequency selective surface has an important significance on preparing a new generation of absorbing coatings with broadband and high temperature resistance.

Road Materials

Mechanical Properties of Cement-Improved Loess Fillerfor Intercity Railway

JIANG Yingjun, ZHANG Wei, LI Qilong, QIAO Huaiyu

2021, 40(7):  2409-2417. 

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In order to reveal the change law of the mechanical properties of the cement-improved loess subgrade fillers on the intercity railway, the influence of cement dosage, compaction coefficient, and curing age on the mechanical properties of the cement-improved loess subgrade fillers were studied through laboratory tests, and the dosage of the improved loess filler cement was optimized. The research shows that the compression strength of 2% (mass fraction, the same below) cement dosage improved loess test piece at 7 d under the compaction coefficient of 0.92 meets the standard value, but the test piece is damaged after soaking; the improved loess sample with cement dosage ≥3% is complete after soaking, and the cement dosage increases by 1%. 28 d compressive strength and splitting strength increase at least 12.3% and 17.0% on average, respectively. The compaction coefficient increases by 0.01, the compressive strength and splitting strength of the improved loess increase by at least 5.4% and 8.0%. The strength growth rate is significantly higher than that of the later stage. The compressive strength and splitting strength of the improved loess specimen with cement dosage ≥3% were about 61% and 45% of their corresponding ultimate strengths, respectively. In order to ensure the strength and bearing capacity of the subgrade, the cement dosage of the embankment below the foundation bed is recommended to be 3% and the compaction coefficient is 0.95. The cement dosage of the embankment to the bottom of the foundation bed is recommended to be 4% and the compaction coefficient is 0.98.

Influencing Factors of Anti-Erosion Performance of Cement Improved Loess

QI Xiaoqiang, YUAN Kejia, CAI Luyao, LIU Haipeng, DONG Xin

2021, 40(7):  2418-2427. 

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To analyze the anti-erosion performance and influencing factors of cement improved loess (CIL), the influences of the compaction method, cement content, compaction coefficient, erosion times on the anti-erosion performance of CIL were studied. Furthermore, the influence of erosion on the strength deterioration of CIL was studied. The results show that compared with the quasi-static compaction method (QSCM), the anti-erosion performance of specimen compacted using the vertical vibration compaction method (VVTM) is better, and the relative erosion mass is reduced by at least 10%. When the cement content increases 1% (mass fraction) and the compaction coefficient increases 0.01, the anti-erosion performance increases 16% and 6.2%, respectively. The erosion times has a significant effect on the quality loss of CIL, and the cumulative erosion mass increases linearly with the increase of erosion times. The compressive strength of CIL decreases significantly due to the erosion, and the average deterioration degree of specimens compacted using VVTM is 79.5%, and that of specimens compacted using QSCM is 73.7%.

Performance Test Analysis of Smoke Suppression Environment-Friendly Asphalt

SUN Jishu, WANG Yaping, WANG Pengfei, YANG Chunfeng

2021, 40(7):  2428-2436. 

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A large amount of asphalt smoke is released from the asphalt pavement during the building process. The smoke not only causes discomfort to the workers and reduces the construction efficiency, but also causes serious environmental pollution. In order to reduce the emission of toxic gases generated during the construction of asphalt pavement, the smoke suppressant was added into 70^# base asphalt, so as to prepare smoke suppression asphalt, and the performance of smoke suppression asphalt was analysed. The effects of different dosages of Sasobit and nano-CaCO₃ added into asphalt with the method of alone mixing or compounding on the smoke suppresseion effect of asphalt were researched by self-made asphalt smoke collecting device. The effects of Sasobit and nano-CaCO₃ on the high temperature performance, low temperature performance, and storage stability performance of the asphalt were analyzed by the dynamic shear test, bending rheological test, and storage stability test. The test results show that Sasobit and nano-CaCO₃ in the optimal compound ratio can make the asphalt smoke reduce by 12% during the mixing process. The high temperature performance of 70^# matrix asphalt is significantly improved, but the low temperature performance of matrix asphalt is reduced. The combination of Sasobit and nano-CaCO₃ has no effect on the storage stability of matrix asphalt.

Influence of Heat Pipe on Cooling Characteristics and High Temperature Stability of Asphalt Mixture

FENG Zhengang, MA Jinyuan, LIU Chang, WANG Wei, DENG Xinlong, LIN Songshan

2021, 40(7):  2437-2443. 

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In order to effectively improve the high temperature stability of the asphalt pavement, the asphalt mixture rutting specimens without embedded and with embedded heat pipe were prepared based on the principle of the gravity heat pipe cooling.The heating and cooling processes of the rutting specimens were simulated by an oven. The temperature sensor and temperature gun were used to collect the temperature data at different positions of the rutting specimens in real time. The enthalpy change value and temperature gradient in a specific calculation range was analyzed to study the effect of heat pipe on the cooling characteristics of the asphalt mixture rutting specimens. The influence of the heat pipe on the rutting resistance of the asphalt mixture was studied. The results show that the heat pipe can adjust the temperature change of the asphalt mixture to a certain extent, and reduce the influence of temperature on the asphalt mixture. The heat pipe can enhance the dynamic stability and improve the high-temperature rutting resistance of the asphalt mixture significantly.

Phase Structure Analysis of Nano Carbon Powder-Rubber Powder-SBS Modified Asphalt Based on Dynamic Mechanics

WANG Mingwei, XIE Xiangbing, LI Guanghui, LAN Xiang

2021, 40(7):  2444-2453. 

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In order to analyze the phase structure of nano carbon powder, rubber powder and SBS in asphalt, the physical performance test and dynamic shear rheology test (DSR) of matrix asphalt and modified asphalt were first carried out, and secondly, use Han curve theory and vGP diagram analysis the compatibility and phase structure of three modifiers and matrix asphalt. The results show that under the same test conditions, 2% nano carbon powder-18% rubber powder-1.0% SBS (all above are mass fraction) modified asphalt has the best physical properties and better high-temperature stability. Compared with matrix asphalt, the asphalt with modifier the material exhibits microscopic phase separation. Under high temperature conditions, the phase structure of nano carbon powder-rubber powder-SBS modified asphalt is better. Combining the SEM images to explain the modification mechanism, it is concluded that the SBS modifier can effectively improve the skeleton structure system of nano carbon powder and rubber powder in asphalt.

Dynamic Viscoelastic Properties of Hot Recycled Asphalt Mixture Based on CAM Model

LAN Jianli, GAO Xuekai, KONG Fansheng

2021, 40(7):  2454-2460. 

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In order to study the influences of regenerants on the dynamic properties of the asphalt mixture, the heavy petroleum-based and bio-oil-based regenerants were selected to prepare the recycled asphalt and the asphalt mixture. Through the penetration, softening point, dyctility tests of the asphalt and the dynamic modulus tests of the asphalt mixture under different regenerant content, the dynamic of the recycled asphalt mixture were analyzed according to the principle of time-temperature equivalence and the improved Christensen-Anderson-Marasteanu (CAM) model. The results show that with the increase of the regenerant content, the penetration and ductility of the asphalt in RAP increase, and the softening point decreases. The incorporation of the regenerant significantly improves the ductility of the asphalt. Taking into account the economy and road performance, 12% (mass fraction) is the best content of the regenerant. Both types of regenerants change the temperature sensitivity and viscoelastic properties of RAP, so that the dynamic modulus of the recycled asphalt mixture is reduced and the phase angle increases. The improved CAM mode can fit the dynamic modulus and phase angle of the recycled asphalt mixture with the development of frequency very well, and the fitting accuracy is above 0.950. The dynamic modulus and phase angle of the two recycled asphalt mixtures are affected by the loading frequency. When the loading frequency is higher than 10 Hz, the bio-oil-based recycled asphalt mixture has a lower dynamic modulus and a higher phase angle than the petroleum-based recycled asphalt mixture, while the result is the opposite when the loading frequency is lower than 0.01 Hz, such the dynamic viscoelastic properties are beneficial for improving the high temperature stability and low temperature crack resistance of the asphalt mixture at the same time.

Rheological Properties of Graphene/Polyethylene Composite Modified Asphalt Binder

LI Baoyu

2021, 40(7):  2461-2468. 

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To improve the overall road performance of asphalt binders, especially the high temperature performance, a new asphalt binder was prepared by combining high-quality and inexpensive polyethylene (PE) with graphene nanoplatelets (GNPs) with a high-speed shear mixer. Meanwhile, the rheological properties and action mechanism of the composite modified asphalt binders were subsequently investigated using temperature sweep (TeS), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), bending beam rheometer (BBR), and fourier transform infrared spectroscopy (FTIR). The results show that GNPs and PE synergistically improve the high-temperature performance of asphalt binders and enhance the high-temperature rutting resistance of pavements; the pre-blended PE/GNPs masterbatch has good medium-temperature fatigue and low-temperature cracking resistance. Meanwhile, no new absorption peaks appeared in the FTIR spectra of the composite modified asphalt, indicating that mainly physical co-blending of graphene and polyethylene occurred in the asphalt matrix.