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Appraising the potential of calcium sulfoaluminate cement-based grouts in simulated permafrost environments

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 722-731 doi: 10.1007/s11709-023-0950-5

摘要： The aim of this study is to appraise the potential of calcium sulfoaluminate (CSA) cement-based grouts in simulated permafrost environments. The hydration and performance of CSA cement-based grouts cured in cold environments (10, 0, and −10 °C) are investigated using a combination of tests, including temperature recording, X-ray diffraction (XRD) tests, thermogravimetric analysis (TGA), and unconfined compressive strength (UCS) tests. The recorded temperature shows a rapid increase in temperature at the early stage in all the samples. Meanwhile, results of the TGA and XRD tests show the generation of a significant quantity of hydration products, which indicates the rapid hydration of CSA cement-based grouts at the early stage at low temperatures. Consequently, the CSA cement-based grouts exhibit remarkably high early strength. The UCS values of the samples cured for 2 h at −10, 0, and 10 °C are 6.5, 12.0, and 12.3 MPa, respectively. The UCS of the grouts cured at −10, 0, and 10 °C increases continuously with age and ultimately reached 14.9, 19.0, and 30.6 MPa at 28 d, respectively. The findings show that the strength of grouts fabricated using CSA cement can develop rapidly in cold environments, thus rendering them promising for permafrost applications.

关键词： permafrost     low temperatures     calcium sulfoaluminate cement-based grouts     hydration reaction     compressive strength    

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Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends: Its effects on setting, workability, and strength development

《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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Thermodynamic analysis of ethanol synthesis from hydration of ethylene coupled with a sequential reaction

Jie Gao, Zhikai Li, Mei Dong, Weibin Fan, Jianguo Wang

《化学科学与工程前沿（英文）》 2020年 第14卷 第5期   页码 847-856 doi: 10.1007/s11705-019-1848-6

摘要： Coal-based ethanol production by hydration of ethylene is limited by the low equilibrium ethylene conversion at elevated temperature. To improve ethylene conversion, coupling hydration of ethylene with a potential ethanol consumption reaction was analyzed thermodynamically. Five reactions have been attempted and compared: (1) dehydration of ethanol to ethyl ether ( ), (2) dehydrogenation of ethanol to acetaldehyde ( ), (3) esterification of acetic acid with ethanol ( ), (4) dehydrogenation of ethanol to ethyl acetate ( ), and (5) oxidative dehydrogenation of ethanol to ethyl acetate ( ). The equilibrium constants and equilibrium distributions of the coupled reactions were calculated and the effects of feed composition, temperature and pressure upon the ethylene equilibrium conversion were examined. The results show that dehydrogenation of ethanol to acetaldehyde has little effect on ethylene conversion, whereas for dehydrogenation of ethanol to acetaldehyde and ethyl acetate, ethylene conversion can be improved from 8% to 12.8% and 18.5%, respectively, under conditions of H O/C H = 2, 10 atm and 300°C. The esterification of acetic acid with ethanol can greatly enhance the ethylene conversion to 22.5%; in particular, ethylene can be actually completely converted to ethyl acetate by coupling oxidative dehydrogenation of ethanol.

关键词： ethylene     ethanol     thermodynamics     coupling    

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A general framework for modeling long-term behavior of earth and concrete dams

Bernhard A. SCHREFLER, Francesco PESAVENTO, Lorenzo SANAVIA, Giuseppe SCIUME, Stefano SECCHI, Luciano SIMONI

《结构与土木工程前沿（英文）》 2011年 第5卷 第1期   页码 41-52 doi: 10.1007/s11709-010-0070-x

摘要： Many problems are linked with the long-term behavior of both earthdams and concrete dams. They range from hydraulic fracturing to alkali-silica reaction (ASR) and to repair work in concrete dams, from seismic behavior to secondary consolidation in earthdams. A common framework for the simulation of such systems is shown, based on the mechanics of multiphase porous media. The general model is particularized to specific situations and several examples are shown.

关键词： earth dams     concrete dams     multiphase porous materials     coupled problems     hydraulic fracture     concrete hydration     alkali-silica reaction (ASR)     finite element method    

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Quantification of hydration products in cementitious materials incorporating silica nanoparticles

L. P. SINGH,A. GOEL,S. K. BHATTACHARYYA,G. MISHRA

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 162-167 doi: 10.1007/s11709-015-0315-9

摘要： In the present work, silica nanoparticles (30-70nm) were supplemented into cement paste to study their influence on degree of hydration, porosity and formation of different type of calcium-silicate-hydrate (C-S-H) gel. As the hydration time proceeds, the degree of hydration reach to 76% in nano-modified cement paste whereas plain cement achieve up to 63% at 28 days. An influence of degree of hydration on the porosity was also determined. In plain cement paste, the capillary porosity at 1hr is ~48%, whereas in silica nanoparticles added cement is ~35 % only, it revealed that silica nanoparticles refines the pore structure due to accelerated hydration mechanism leading to denser microstructure. Similarly, increasing gel porosity reveals the formation of more C-S-H gel. Furthermore, C-S-H gel of different Ca/Si ratio in hydrated cement paste was quantified using X-ray diffractometer and thermogravimetry. The results show that in presence of silica nanoparticles, ~24% C-S-H (Ca/Si<1.0) forms, leading to the formation of polymerised and compact C-S-H. In case of plain cement this type of C-S-H was completely absent at 28 days. These studies reveal that the hydration mechanism of the cement can be tuned with the incorporation of silica nanoparticles and thus, producing more durable cementitious materials.

关键词： degree of hydration     porosity     calcium-silicate-hydrate (C-S-H)     silica nanoparticles    

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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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预制拼装箱梁现浇横隔梁水化热分析与控制研究

陈扬,钟瑶,郑开启,沈斌,孟少平

《中国工程科学》 2013年 第15卷 第8期   页码 99-103

摘要：

在节段预制拼装桥梁的墩顶节段，常常采用后浇横隔梁的方式来减轻吊装重量。后浇横隔梁在体量上属于大体积混凝土，混凝土水化热问题会引起一些部位拉应力过大，如控制措施不合理，往往会导致预制梁段在施工阶段的开裂。本文结合南京长江第四大桥的引桥工程，基于三维瞬态温度场理论，利用通用有限元程序ANSYS对墩顶梁段现浇块的水化热效应进行了数值仿真，研究箱梁水化热温度场和应力场的分布规律。分析结果表明，水化热引起的箱梁腹板外侧拉应力水平足以导致混凝土开裂，在水化热测试试验中也观测到了箱梁腹板外侧的纵向微裂缝，与分析相符。在研究水化热温度场和应力场分布规律的基础上，进行了控制水化热温度应力的措施研究，在实桥施工中证实是切实有效的。

关键词： 混凝土箱梁     水化热     温度场     应力场     裂缝    

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Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

《化学科学与工程前沿（英文）》 2022年 第16卷 第12期   页码 1700-1712 doi: 10.1007/s11705-022-2207-6

摘要： The chain length and hydrocarbon type significantly affect the production of light olefins during the catalytic pyrolysis of naphtha. Herein, for a better catalyst design and operation parameters optimization, the reaction pathways and equilibrium yields for the catalytic pyrolysis of C5–8 n/iso/cyclo-paraffins were analyzed thermodynamically. The results revealed that the thermodynamically favorable reaction pathways for n/iso-paraffins and cyclo-paraffins were the protolytic and hydrogen transfer cracking pathways, respectively. However, the formation of light paraffin severely limits the maximum selectivity toward light olefins. The dehydrogenation cracking pathway of n/iso-paraffins and the protolytic cracking pathway of cyclo-paraffins demonstrated significantly improved selectivity for light olefins. The results are thus useful as a direction for future catalyst improvements, facilitating superior reaction pathways to enhance light olefins. In addition, the equilibrium yield of light olefins increased with increasing the chain length, and the introduction of cyclo-paraffin inhibits the formation of light olefins. High temperatures and low pressures favor the formation of ethylene, and moderate temperatures and low pressures favor the formation of propylene. n-Hexane and cyclohexane mixtures gave maximum ethylene and propylene yield of approximately 49.90% and 55.77%, respectively. This work provides theoretical guidance for the development of superior catalysts and the selection of proper operation parameters for the catalytic pyrolysis of C5–8 n/iso/cyclo-paraffins from a thermodynamic point of view.

关键词： naphtha     catalytic pyrolysis     reaction pathway     equilibrium yield    

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Effect of a commercial dispersion of multi walled carbon nanotubes on the hydration of an oil well cementing

Ocar Aurelio MENDOZA REALES,William C.PEARL Jr,Maria D. M. PAIVA,CristianeR. MIRANDA,Romildo Dias TOLEDO FILHO

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 174-179 doi: 10.1007/s11709-015-0324-8

摘要： This work studies the influence of a commercial dispersion of multi wall carbon nanotubes (MWCNT) on the hydration of a class G cement paste, at room and elevated down-hole temperatures. The MWCNT dispersion was produced with a solids concentration of 3.0 % by mass and an anionic surfactant as dispersing agent. Cement pastes with water-to-cement ratio of 0.45 and additions of solid MWCNT by mass of cement up to 0.50 % were studied. Isothermal calorimetry results showed a clear retardation of the hydration of cement caused by the surfactant contained in the MWCNT dispersion. Nevertheless, thermogravimetric evaluations showed that once the hydration reaction resumed, the retardation effect of the surfactant did not have a negative impact on the amount of hydration products precipitated. It was concluded that the commercial MWCNT dispersion presents a good potential to be applied in oil well cement pastes.

关键词： carbon nanotubes     surfactant     retardation     combined water     C-S-H    

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碱激发矿渣混凝土的水化特性及微观结构研究进展 Review

傅强,卜梦鑫, 张兆瑞, 许文瑞, 元强, 牛荻涛

《工程（英文）》 2023年 第20卷 第1期   页码 162-179 doi: 10.1016/j.eng.2021.07.026

摘要：

碱激发矿渣混凝土（alkali-activated slag concrete, AASC）是一种新型的绿色建材，与普通硅酸盐混凝土相比，制备AASC所产生的CO2仅为普通硅酸盐混凝土（ordinary Portland cement concrete, OPCC）的1/5；另外，AASC促进了矿渣等废弃物的再利用，节约了资源，扩大了矿渣的使用范围。本文根据AASC的相关研究，分析总结了AASC的水化特性以及界面过渡区、孔结构等微观结构的研究进展。讨论了矿渣成分、碱激发剂种类及其用量、养护条件对AASC的水化特性和微观结构的影响。目前关于AASC微观结构的研究成果相对较少，相关结论还未完全统一，而且，AASC的发展还存在很多制约因素（如矿渣原料成分复杂、收缩变形较大、流动性差等），因此，还需要进一步的深入研究。

关键词： 碱激发矿渣混凝土     水化特性     孔结构     界面过渡区     微观结构    

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Compressive behavior and microstructure of concrete mixed with natural seawater and sea sand

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1347-1357 doi: 10.1007/s11709-021-0780-2

摘要： Noncorrosive reinforcement materials facilitate producing structural concrete with seawater and sea sand. This study investigated the properties of seawater and sea sand concrete (SSC), considering the curing age (3, 7, 14, 21, 28, 60, and 150 d) and strength grade (C30, C40, and C60). The compressive behavior of SSC was obtained by compressive tests and digital image correction (DIC) technique. Scanning electron microscope (SEM) and X-ray powder diffraction (XRD) methods were applied to understand the microstructure and hydration products of cement in SSC. Results revealed a 30% decrease in compressive strength for C30 and C40 SSC from 60 to 150 d, and a less than 5% decrease for C60 from 28 to 150 d. DIC results revealed significant cracking and crushing from 80% to 100% of compressive strength. SEM images showed a more compact microstructure in higher strength SSC. XRD patterns identified Friedel’s salt phase due to the chlorides brought by seawater and sea sand. The findings in this study can provide more insights into the microstructure of SSC along with its short- and long-term compressive behavior.

关键词： seawater and sea sand concrete     compressive strength     strain field     microstructure     hydration products    

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混凝土的裂缝与控制

缪昌文,刘建忠,田倩

《中国工程科学》 2013年 第15卷 第4期   页码 30-35

摘要：

在分析混凝土开裂的危害和产生原因的基础上，提出裂缝控制新技术。采用双亲性单分子膜，减少混凝土早期的水分蒸发，抑制混凝土早期因失水太快而产生的塑性收缩裂缝；采用减水与减缩共同作用，控制混凝土壳体及薄壁结构的早期开裂；采用调控水泥水化过程中的放热量，提高大体积混凝土的温控能力；采用遥爪聚合型增韧剂，增加混凝土的韧性，减少混凝土的脆性开裂。

关键词： 混凝土     裂缝     收缩     水化热     韧性    

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催化裂化过程反应化学的进展

许友好,汪燮卿

《中国工程科学》 2007年 第9卷 第8期   页码 6-14

摘要：

面对催化裂化工艺所遇到的挑战，提出了催化裂化过程反应化学的多维反应结构模式。多维反应结构模式的建立是基于对烃类在酸性催化剂上反应化学认识而进行的知识创新，但多维反应结构不同于烃类在酸性催化剂上反应化学。具有多维反应结构的催化裂化工艺更具有多样性和灵活性，基于此已成功地开发了多产异构烷烃的催化裂化工艺和生产清洁汽油和多产丙烯的催化裂化工艺。

关键词： 催化裂化     反应化学     催化剂     多维反应结构     两个反应区    

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Heterogeneous reaction mechanism of gaseous HNO

Nan ZHAO,Qingzhu ZHANG,Wenxing WANG

《环境科学与工程前沿（英文）》 2016年 第10卷 第5期 doi: 10.1007/s11783-016-0836-z

摘要： We studied the heterogeneous reaction mechanism of gaseous HNO with solid NaCl. HCl is released from heterogeneous reactions between gaseous HNO and solid NaCl. Water molecules induce surface reconstruction of NaCl to facilitate the reaction. Sea salt particles containing NaCl are among the most abundant particulate masses in coastal atmosphere. Reactions involving sea salt particles potentially generate Cl radicals, which are released into coastal atmosphere. Cl radicals play an important role in the nitrogen and O cycles, sulfur chemistry and particle formation in the troposphere of the polluted coastal regions. This paper aimed at the heterogeneous reaction between gaseous HNO and solid NaCl. The mechanism was investigated by density functional theory (DFT). The results imply that water molecules induce the surface reconstruction, which is essential for the heterogeneous reaction. The surface reconstruction on the defective (710) surface has a barrier of 10.24 kcal·mol and is endothermic by 9.69 kcal·mol , whereas the reconstruction on the clean (100) surface has a barrier of 18.46 kcal·mol and is endothermic by 12.96 kcal·mol . The surface reconstruction involved in water-adsorbed (710) surface is more energetically favorable. In comparison, water molecules adsorbed on NaCl (100) surface likely undergo water diffusion or desorption. Further, it reveals that the coordination number of the Cl is reduced after the surface reconstruction, which assists Cl to accept the proton from HNO . HCl is released from heterogeneous reactions between gaseous HNO and solid NaCl and can react with OH free radicals to produce atomic Cl radicals. The results will offer further insights into the impact of gaseous HNO on the air quality of the coastal areas.

关键词： Seasalt particles     NaCl     HNO3     Heterogeneous reaction     Reaction mechanism     Density functional theory    

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Dual-reaction-center catalytic process continues Fenton’s story

Chao Lu, Kanglan Deng, Chun Hu, Lai Lyu

《环境科学与工程前沿（英文）》 2020年 第14卷 第5期 doi: 10.1007/s11783-020-1261-x

摘要： Abstract • Dual-reaction-center (DRC) system breaks through bottleneck of Fenton reaction. • Utilization of intrinsic electrons of pollutants is realized in DRC system. • DRC catalytic process well continues Fenton’s story. Triggered by global water quality safety issues, the research on wastewater treatment and water purification technology has been greatly developed in recent years. The Fenton technology is particularly powerful due to the rapid attack on pollutants by the generated hydroxyl radicals (•OH). However, both heterogeneous and homogeneous Fenton/Fenton-like technologies follow the classical reaction mechanism, which depends on the oxidation and reduction of the transition metal ions at single sites. So even after a century of development, this reaction still suffers from its inherent bottlenecks in practical application. In recent years, our group has been focusing on studying a novel heterogeneous Fenton catalytic process, and we developed the dual-reaction-center (DRC) system for the first time. In the DRC system, H2O2 and O2 can be efficiently reduced to reactive oxygen species (ROS) in electron-rich centers, while pollutants are captured and oxidized by the electron-deficient centers. The obtained electrons from pollutants are diverted to the electron-rich centers through bonding bridges. This process breaks through the classic Fenton mechanism, and improves the performance and efficiency of pollutant removal in a wide pH range. Here, we provide a brief overview of Fenton’s story and focus on combing the discovery and development of the DRC technology and mechanism in recent years. The construction of the DRC and its performance in the pollutant degradation and interfacial reaction process are described in detail. We look forward to bringing a new perspective to continue Fenton’s story through research and development of DRC technology.

关键词： Dual reaction centers     Fenton     Pollutant utilization     Electron transfer    

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标题 作者 时间 类型 操作

Appraising the potential of calcium sulfoaluminate cement-based grouts in simulated permafrost environments

期刊论文

Extending blending proportions of ordinary Portland cement and calcium sulfoaluminate cement blends: Its effects on setting, workability, and strength development

期刊论文

Thermodynamic analysis of ethanol synthesis from hydration of ethylene coupled with a sequential reaction

Jie Gao, Zhikai Li, Mei Dong, Weibin Fan, Jianguo Wang

期刊论文

A general framework for modeling long-term behavior of earth and concrete dams

Bernhard A. SCHREFLER, Francesco PESAVENTO, Lorenzo SANAVIA, Giuseppe SCIUME, Stefano SECCHI, Luciano SIMONI

期刊论文

Quantification of hydration products in cementitious materials incorporating silica nanoparticles

L. P. SINGH,A. GOEL,S. K. BHATTACHARYYA,G. MISHRA

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

预制拼装箱梁现浇横隔梁水化热分析与控制研究

陈扬,钟瑶,郑开启,沈斌,孟少平

期刊论文

Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

期刊论文

Effect of a commercial dispersion of multi walled carbon nanotubes on the hydration of an oil well cementing

Ocar Aurelio MENDOZA REALES,William C.PEARL Jr,Maria D. M. PAIVA,CristianeR. MIRANDA,Romildo Dias TOLEDO FILHO

期刊论文

碱激发矿渣混凝土的水化特性及微观结构研究进展

傅强,卜梦鑫, 张兆瑞, 许文瑞, 元强, 牛荻涛

期刊论文

Compressive behavior and microstructure of concrete mixed with natural seawater and sea sand

期刊论文

混凝土的裂缝与控制

缪昌文,刘建忠,田倩

期刊论文

催化裂化过程反应化学的进展

许友好,汪燮卿

期刊论文

Heterogeneous reaction mechanism of gaseous HNO

Nan ZHAO,Qingzhu ZHANG,Wenxing WANG

期刊论文

Dual-reaction-center catalytic process continues Fenton’s story

Chao Lu, Kanglan Deng, Chun Hu, Lai Lyu

期刊论文