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Long-Term Performance and Microstructural Characterization of Dam Concrete in the Three Gorges Project

Chen Lyu,Cheng Yu,Chao Lu,Li Pan,Wenwei Li,Jiaping Liu,

《工程（英文）》 doi: 10.1016/j.eng.2023.04.017

摘要： This study investigates the long-term performance of laboratory dam concrete in different curing environments over ten years and the microstructure of 17-year-old laboratory concrete and actual concrete cores drilled from the Three Gorges Dam. The mechanical properties of the laboratory dam concrete, whether cured in natural or standard environments, continued to improve over time. Furthermore, the laboratory dam concrete exhibited good resistance to diffusion and a refined microstructure after 17 years. However, curing and long-term exposure to the local natural environment reduced the frost resistance. Microstructural analyses of the laboratory concrete samples demonstrated that moderate-heat cement and fine fly ash (FA) particles were almost fully hydrated to form compact microstructures consisting of large quantities of homogeneous C-(A)-S-H gels and a few crystals. No obvious interfacial transition zones were observed in the microstructure owing to the long-term pozzolanic reaction. This dense and homogenous microstructure was the crucial reason for the excellent long-term performance of the dam concrete. A high FA volume also played a significant role in the microstructural densification and performance growth of dam concrete at a later age. The concrete drilled from the dam surface exhibited a loose microstructure with higher microporosity, indicating that concrete directly exposed to the actual service environment suffered degradation caused by water and wind attacks. In this study, both macro performance and microstructural analyses revealed that the application of moderate-heat cement and FA resulted in a dense and homogenous microstructure, which ensured the excellent long-term performance of concrete from the Three Gorges Dam after 17 years. Long-term exposure to an actual service environment may lead to microstructural degradation of the concrete surface. Therefore, the retained long-term dam concrete samples need to be further researched to better understand its microstructural evolution and development of its properties.

关键词： Three Gorges Dam     Long-term performance     Microstructural analysis     Moderate-heat cement     Fly ash    

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Recovery of waste heat in cement plants for the capture of CO

Ruifeng DONG, Zaoxiao ZHANG, Hongfang LU, Yunsong YU

《化学科学与工程前沿（英文）》 2012年 第6卷 第1期   页码 104-111 doi: 10.1007/s11705-011-1166-0

摘要： Large amounts of energy are consumed during the manufacturing of cement especially during the calcination process which also emits large amounts of CO . A large part of the energy used in the making of cement is released as waste heat. A process to capture CO by integrating the recovery and utilization of waste heat has been designed. Aspen Plus software was used to calculate the amount of waste heat and the efficiency of energy utilization. The data used in this study was based on a dry process cement plant with a 5-stage preheater and a precalciner with a cement output of 1 Mt/y. According to the calculations: 1) the generating capacity of the waste heat recovery system is 4.9 MW. 2) The overall CO removal rate was as high as 78.5%. 3) The efficiency of energy utilization increased after the cement producing process was retrofitted with this integrated design.

关键词： cement industry     waste heat     recovery     utilization     CO2 removal    

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Characterization of 3D microstructure, thermal conductivity, and heat flow of cement-based foam using

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 643-651 doi: 10.1007/s11709-021-0709-9

摘要： This study presents the results of the 3D microstructure, thermal conductivity, and heat flow in cement-based foams and examines their changes with a range of densities. Images were captured using X-ray micro computed tomography (micro-CT) imaging technique on cement-based foam samples prepared with densities of 400, 600, and 800 kg/m3. These images were later simulated and quantified using 3D data visualization and analysis software. Based on the analysis, the pore volume of 11000 µm3 was determined across the three densities, leading to optimal results. However, distinct pore diameters of 15 µm for 800 kg/m3, and 20 µm for 600 and 400 kg/m3 were found to be optimum. Most of the pores were spherical, with only 10% appearing elongated or fractured. In addition, a difference of 15% was observed between the 2D and 3D porosity results. Moreover, a difference of 5% was noticed between the experimentally measured thermal conductivity and the numerically predicted value and this variation was constant across the three cast densities. The 3D model showed that heat flows through the cement paste solids and with an increase in porosity this flow reduces.

关键词： 3D pore volume distribution     X-ray tomography     3D shape factor     heat flow    

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Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent

Beibei SUN, Hao WU, Weimin SONG, Zhe LI, Jia YU

《结构与土木工程前沿（英文）》 2020年 第14卷 第5期   页码 1274-1284 doi: 10.1007/s11709-020-0656-x

摘要： Superabsorbent Polymer (SAP) has emerged as a topic of considerable interest in recent years. The present study systematically and quantitively investigated the effect of SAP on hydration, autogenous shrinkage, mechanical properties, and microstructure of cement mortars. Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method. Scanning Electron Microscope (SEM) was employed to assess the microstructure evolution. Although SAP decreased the peak rate of hydration heat and retarded the hydration, it significantly increased the cumulative heat, indicating SAP helps promote the hydration. Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period. SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%. Microstructure characteristics showed that pores and gaps were introduced when SAP was added. The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP.

关键词： Superabsorbent Polymer     mechanical properties     hydration heat     autogenous shrinkage     microstructure    

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Effect of potassium carbonate on catalytic synthesis of calcium carbide at moderate temperature

Dejun SHI, Ke QIAO, Zifeng YAN

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 372-375 doi: 10.1007/s11705-010-0570-1

摘要： Calcium carbide was successfully synthesized by carbothermal reduction of lime with coke at 1973 K for 1.5 h. The effect of potassium carbonate as additive on the composition and morphology of the product was investigated using X-ray diffraction and scanning electron microscope. Addition of potassium carbonate increased the yield of calcium carbide. The sample in the presence of potassium carbonate generated acetylene gas of 168.3 L/kg, which was 10% higher than that in the absence of potassium carbonate. This result confirmed the catalytic effect of potassium carbonate on the synthesis of calcium carbide. A possible mechanism of the above effects was that the additive, which was melted at the reduction temperature, dissolved CaO and so promoted the contact between CaO and carbon, which was essential for the solid-solid reaction to form calcium carbide.

关键词： calcium carbide     synthesis     catalysis    

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Development of an H reduction and moderate oxidation method for 3,5-dimethylpyridine hydrogenation in

《化学科学与工程前沿（英文）》 2022年 第16卷 第12期   页码 1807-1817 doi: 10.1007/s11705-022-2243-2

摘要： The Ru/C catalyst prepared by impregnation method was used for hydrogenation of 3,5-dimethylpyridine in a trickle bed reactor. Under the same reduction conditions (300 °C in H2), the catalytic activity of the non-in-situ reduced Ru/C-n catalyst was higher than that of the in-situ reduced Ru/C-y catalyst. Therefore, an in-situ H2 reduction and moderate oxidation method was developed to increase the catalyst activity. Moreover, the influence of oxidation temperature on the developed method was investigated. The catalysts were characterized by Brunauer–Emmett–Teller method, hydrogen temperature programmed reduction H2-TPR, hydrogen temperature-programmed dispersion (H2-TPD), X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, O2 chemisorption and oxygen temperature-programmed dispersion (O2-TPD) analyses. The results showed that there existed an optimal Ru/RuOx ratio for the catalyst, and the highest 3,5-dimethylpyridine conversion was obtained for the Ru/C-i1 catalyst prepared by in-situ H2 reduction and moderate oxidation (oxidized at 100 °C). Excessive oxidation (200 °C) resulted in a significant decrease in the Ru/RuOx ratio of the in-situ H2 reduction and moderate oxidized Ru/C-i2 catalyst, the interaction between RuOx species and the support changed, and the hard-to-reduce RuOx species was formed, leading to a significant decrease in catalyst activity. The developed in-situ H2 reduction and moderate oxidation method eliminated the step of the non-in-situ reduction of catalyst outside the trickle bed reactor.

关键词： Ru/C catalyst     in-situ H2 reduction and moderate oxidation     in-situ reduction     non-in-situ reduction     hydrogenation of 3     5-dimethylpyridine    

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Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends:

《结构与土木工程前沿（英文）》 2021年 第15卷 第5期   页码 1249-1260 doi: 10.1007/s11709-021-0770-4

摘要： This study extended blending proportion range of ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement blends, and investigated effects of proportions on setting time, workability, and strength development of OPC-CSA blend-based mixtures. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to help understand the performance of OPC-CSA blend-based mixtures. The setting time of the OPC-CSA blends was extended, and the workability was improved with increase of OPC content. Although the early-age strength decreased with increase of OPC content, the strength development was still very fast when the OPC content was lower than 60% due to the rapid formation and accumulation of ettringite. At 2 h, the OPC-CSA blend-based mortars with OPC contents of 0%, 20%, 40%, and 60% achieved the unconfined compressive strength (UCS) of 17.5, 13.9, 9.6, and 5.0 MPa, respectively. The OPC content had a negligible influence on long-term strength. At 90 d, the average UCS of the OPC-CSA blend-based mortars was 39.2 ± 1.7 MPa.

关键词： calcium sulfoaluminate cement     cement blends     hydration reaction     setting     workability     compressive strength    

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Key technical innovations in the construction of Baihetan Hydropower Station Project

《工程管理前沿（英文）》 2023年 第10卷 第2期   页码 367-372 doi: 10.1007/s42524-023-0253-5

摘要： Key technical innovations in the construction of Baihetan Hydropower Station Project

关键词： ultra-high arch dam     columnar jointed basalt     low-heat cement concrete     temperature controlled crack prevention     million-kilowatt unit     intelligent construction    

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ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of cementmortar; influence of cement fineness and water/cement ratio

《结构与土木工程前沿（英文）》 2022年 第16卷 第2期   页码 191-201 doi: 10.1007/s11709-021-0792-y

摘要： A new insight into the interfacial transition zone (ITZ) in cement mortar specimens (CMSs) that is influenced by cement fineness is reported. The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive (Fc) and flexural strength (Ff), and porosity at various water/cement ratios. The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure. By increasing cement fineness by about 25% of, the ITZ thickness of CMSs was reduced by about 30% and Fc was increased by 7%–52% and Ff by 19%–40%. These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词： cement fineness     interfacial transition zone     compressive and flexural strength    

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地下矿山中深孔落矿爆破块度控制技术研究

赵艳伟,何冬梅,李祥龙,刘俊轩

《中国工程科学》 2014年 第16卷 第11期   页码 48-52

摘要：

扇形中深孔爆破的落矿方式在大红山铜矿中的应用占总采矿量的61 %以上，但大块产出率较高严重制约着矿山供矿强度，平均大块率高达22.7 %。为了降低大块率，实现矿山生产的高效发展，提出采用环形中深孔爆破落矿工艺并进行了现场试验，试验结果表明环形中深孔爆破落矿可使平均大块率降低至10.3 %，与传统扇形中深孔落矿相比较，平均大块率降低了12.4 %，使盘区当班日供矿量增加152.29 t，增长率为51.1 %；减少了处理大块所耽误的时间和二次破碎的炸药与雷管的消耗，在提高出矿效率的同时，降低了落矿成本，取得了良好的爆破效果。

关键词： 扇形中深孔爆破     环形中深孔爆破     大块率     爆破效果    

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Study of bond strength between various grade of Ordinary Portland Cement (OPC) and Portland PozzolaneCement (PPC) mixes and different diameter of TMT bars by using pullout test

A D POFALE, S P WANJARI

《结构与土木工程前沿（英文）》 2013年 第7卷 第1期   页码 39-45 doi: 10.1007/s11709-013-0193-y

摘要： Since last two decades, the Portland Pozzolane Cement (PPC) is extensively used in structural concrete. But, till to date, a few literature is available on bond strength of concrete using PPC mixes. There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement (OPC). Hence, a comparative study was conducted on bond strength between OPC and PPC mixes. In the present investigation, total 24 samples consisting of M20, M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days. The pullout bond test was conducted on each specimen as per IS: 2770-1967/1997 [1] and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress. It was observed that the critical bond strength of PPC mixes is 10% higher than OPC mixes. Whereas, marginal improvement was noticed in maximum bond strength of PPC mixes. Hence, based on these findings, it could be concluded that development length for PPC mixes could be reduced by 10% as compared with same grade of OPC mixes.

关键词： bond strength     Portland Pozzolane Cement (PPC) concrete     Ordinary Portland Cement (OPC) concrete     bond between concrete and steel     pullout test     development length    

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Autogenous healing mechanism of cement-based materials

《结构与土木工程前沿（英文）》   页码 948-963 doi: 10.1007/s11709-023-0960-3

摘要： Autogenous self-healing is the innate and fundamental repair capability of cement-based materials for healing cracks. Many researchers have investigated factors that influence autogenous healing. However, systematic research on the autogenous healing mechanism of cement-based materials is lacking. The healing process mainly involves a chemical process, including further hydration of unhydrated cement and carbonation of calcium oxide and calcium hydroxide. Hence, the autogenous healing process is influenced by the material constituents of the cement composite and the ambient environment. In this study, different factors influencing the healing process of cement-based materials were investigated. Scanning electron microscopy and optical microscopy were used to examine the autogenous healing mechanism, and the maximum healing capacity was assessed. Furthermore, detailed theoretical analysis and quantitative detection of autogenous healing were conducted. This study provides a valuable reference for developing an improved healing technique for cement-based composites.

关键词： autogenous healing     cement-based materials     healing mechanism     aggregation effect    

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Research review of the cement sand and gravel (CSG) dam

Xin CAI, Yingli WU, Xingwen GUO, Yu MING

《结构与土木工程前沿（英文）》 2012年 第6卷 第1期   页码 19-24 doi: 10.1007/s11709-012-0145-y

摘要： The cement sand and gravel (CSG) dam is a new style of dam that owes the advantages both of the concrete faced rock-fill dam (CRFD) and roller compacted concrete (RCC) gravity dam, because of which it has attracted much attention of experts home and abroad. At present, some researches on physic-mechanical property of CSG material and work behavior of CSG dam have been done. This paper introduces the development and characteristics of CSG dam systematically, and summarizes the progress of the study on basic tests, constitutive relation of CSG material and numerical analysis of CSG dam, in addition, indicates research and application aspect of the dam.

关键词： cement sand and gravel (CSG) dam     cement sand and gravel (CSG) material     research review    

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Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete

Yanhua GUAN, Ying GAO, Renjuan SUN, Moon C. WON, Zhi GE

《结构与土木工程前沿（英文）》 2017年 第11卷 第3期   页码 338-345 doi: 10.1007/s11709-017-0411-0

摘要： The fast-track repair of deteriorated concrete pavement requires materials that can be placed, cured, and opened to the traffic in a short period. Type III cement and Calcium Sulfoaluminate (CSA) cement are the most commonly used fast-setting hydraulic cement (FSHC). In this study, the properties of Type III and CSA cement concrete, including compressive strength, coefficient of thermal expansion (CTE) and shrinkage were evaluated. The test results indicate that compressive strength of FSHC concrete increased rapidly at the early age. CSA cement concrete had higher early-age and long term strength. The shrinkage of CSA cement concrete was lower than that of Type III cement concrete. Both CSA and Type III cement concrete had similar CTE values. Based on the laboratory results, the CSA cement was selected as the partial-depth rapid repair material for a distressed continuously reinforced concrete pavement. The data collected during and after the repair show that the CSA cement concrete had good short-term and long-term performances and, therefore, was suitable for the rapid repair of concrete pavement.

关键词： Calcium Sulfoaluminate (CSA) cement     Type III cement     coefficient of thermal expansion (CTE)     shrinkage     rapid repair    

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The effect of SiO

Ismael FLORES-VIVIAN, Rani G.K PRADOTO, Mohamadreza MOINI, Marina KOZHUKHOVA, Vadim POTAPOV, Konstantin SOBOLEV

《结构与土木工程前沿（英文）》 2017年 第11卷 第4期   页码 436-445 doi: 10.1007/s11709-017-0438-2

摘要： The nanoparticles of SiO were used in cement systems to modify the rheological behavior, to enhance the reactivity of supplementary cementitious materials, and also to improve the strength and durability. In this research, low-cost nano-SiO particles from natural hydrothermal solutions obtained by membrane ultrafiltration and, optionally, by cryochemical vacuum sublimation drying, were evaluated in portland cement based systems. ??The SiO -rich solutions were obtained from the wells of Mutnovsky geothermal power station (Far East of Russia). The constant nano-SiO dosage of 0.25% (as a solid material by weight of cementitious materials) was used to compare the cement systems with different nanoparticles against a reference mortar and a commercially available nano-SiO . Nanoparticles were characterized by X-Ray Diffraction (XRD), BET Surface Area, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) spectroscopy techniques. It was demonstrated that the addition of polycarboxylate ether superplasticizer and the dispersion treatment using an ultrasound processor can be used to facilitate the distribution of nano-SiO particles in the mixing water. The effect of nano-SiO particles in portland cement mortars was investigated by evaluating the flow, heat of hydration and compressive strength development. It was demonstrated that the use of nano-SiO particles can reduce the segregation and improve strength properties.

关键词： ultrafiltration     cryochemical vacuum sublimation drying     nanoparticles     portland cement     heat of hydration     surface area     compressive strength    

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标题 作者 时间 类型 操作

Long-Term Performance and Microstructural Characterization of Dam Concrete in the Three Gorges Project

Chen Lyu,Cheng Yu,Chao Lu,Li Pan,Wenwei Li,Jiaping Liu,

期刊论文

Recovery of waste heat in cement plants for the capture of CO

Ruifeng DONG, Zaoxiao ZHANG, Hongfang LU, Yunsong YU

期刊论文

Characterization of 3D microstructure, thermal conductivity, and heat flow of cement-based foam using

期刊论文

Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent

Beibei SUN, Hao WU, Weimin SONG, Zhe LI, Jia YU

期刊论文

Effect of potassium carbonate on catalytic synthesis of calcium carbide at moderate temperature

Dejun SHI, Ke QIAO, Zifeng YAN

期刊论文

Development of an H reduction and moderate oxidation method for 3,5-dimethylpyridine hydrogenation in

期刊论文

Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends:

期刊论文

Key technical innovations in the construction of Baihetan Hydropower Station Project

期刊论文

ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of cementmortar; influence of cement fineness and water/cement ratio

期刊论文

地下矿山中深孔落矿爆破块度控制技术研究

赵艳伟,何冬梅,李祥龙,刘俊轩

期刊论文

Study of bond strength between various grade of Ordinary Portland Cement (OPC) and Portland PozzolaneCement (PPC) mixes and different diameter of TMT bars by using pullout test

A D POFALE, S P WANJARI

期刊论文

Autogenous healing mechanism of cement-based materials

期刊论文

Research review of the cement sand and gravel (CSG) dam

Xin CAI, Yingli WU, Xingwen GUO, Yu MING

期刊论文

Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete

Yanhua GUAN, Ying GAO, Renjuan SUN, Moon C. WON, Zhi GE

期刊论文

The effect of SiO

Ismael FLORES-VIVIAN, Rani G.K PRADOTO, Mohamadreza MOINI, Marina KOZHUKHOVA, Vadim POTAPOV, Konstantin SOBOLEV

期刊论文