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A comprehensive assessment on the durability of gas diffusion electrode materials in PEM fuel cell stack

Arunkumar JAYAKUMAR

《能源前沿（英文）》 2019年第13卷第2期页码 325-338 doi: 10.1007/s11708-019-0618-y

摘要： Polymer electrolyte membrane (PEM) fuel cell is the most promising among the various types of fuel cells. Though it has found its applications in numerous fields, the cost and durability are key barriers impeding the commercialization of PEM fuel cell stack. The crucial and expensive component involved in it is the gas diffusion electrode (GDE) and its degradation, which limits the performance and life of the fuel cell stack. A critical analysis and comprehensive understanding of the structural and functional properties of various materials involved in the GDE can help us to address the related durability and cost issues. This paper reviews the key GDE components, and in specific, the root causes influencing the durability. It also envisages the role of novel materials and provides a critical recommendation to improve the GDE durability.

关键词： PEM fuel cell gas diffusion electrode(GDE) gas diffusion layer(GDL) membrane electrode assembly durability fuel cell catalyst

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Cement mortar with enhanced flexural strength and durability-related properties using

Qing LIU, Renjun LIU, Qiao WANG, Rui LIANG, Zongjin LI, Guoxing SUN

《结构与土木工程前沿（英文）》 2021年第15卷第1期页码 99-108 doi: 10.1007/s11709-021-0721-0

摘要： The low flexural strength and high brittleness of cementitious materials impair their service life in building structures. In this study, we developed a new polymer-modified mortar by polymerization of acrylamide (AM) monomers during the cement setting, which enhanced the flexural and durable performances of mortars. The mechanical properties, micro-and-pore structures, hydrated products, interactions between cement hydrates and polyacrylamide (PAM), and durability-related properties of the mortars were investigated comprehensively. Mortars with 5% PAM exhibited the best performance in terms of flexural strength among all the mixtures. The mechanical strength of cement pastes modified by polymerization of AM monomers was significantly superior to those modified by PAM. The chemical interactions between the polymer molecules and cement hydrates together with the formation of polymer films glued the cement hydrates and polymers and resulted in an interpenetrating network structure, which strengthened the flexural strength. Reductions in porosity and calcium hydroxide content and improvement in capillary water absorption were achieved with the addition of PAM. Finally, the chloride resistance was significantly enhanced with the incorporation of PAM.

关键词： acrylamide in situ polymerization interaction porosity durability

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additives and permeability reducing admixtures having different action mechanisms on mechanical and durability

《结构与土木工程前沿（英文）》 2021年第15卷第5期页码 1277-1291 doi: 10.1007/s11709-021-1752-2

摘要： In this paper, the effect of usage of the permeability reducing admixture (PRA) having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined. For this aim, three commercial PRAs were used during investigation. The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining, respectively. The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property. Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin. The hardened state properties of mortar mixtures such as compressive strength, ultrasonic pulse velocity, water absorption, drying shrinkage and freeze–thaw resistance were investigated. The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties. In this sense, PRA-B, with both insoluble residues and a small amount of air-entraining properties, showed the best performance among the mixtures containing PRA. The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.

关键词： cementitious system mineral additive permeability reducing admixture mechanical properties durability performance

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Experimental investigation on freeze−thaw durability of polymer concrete

《结构与土木工程前沿（英文）》 2021年第15卷第4期页码 1038-1046 doi: 10.1007/s11709-021-0748-2

摘要： Assessing the durability of concrete is of prime importance to provide an adequate service life and reduce the repairing cost of structures. Freeze–thaw is one such test that indicates the ability of concrete to last a long time without a significant loss in its performance. In this study, the freeze–thaw resistance of polymer concrete containing different polymer contents was explored and compared to various conventional cement concretes. Concretes’ fresh and hardened properties were assessed for their workability, air content, and compressive strength. The mass loss, length change, dynamic modulus of elasticity, and residual compressive strength were determined for all types of concretes subjected to freeze–thaw cycles according to ASTM C666-procedure A. Results showed that polymer concrete (PC) specimens prepared with higher dosages of polymer contents possessed better freeze–thaw durability compared to other specimens. This high durability performance of PCs is mainly due to their impermeable microstructures, absence of water in their structure, and the high bond strength between aggregates and a polymer binder. It is also indicated that the performance of high-strength concrete containing air-entraining admixture is comparable with PC having optimum polymer content in terms of residual compressive strength, dynamic modulus of elasticity, mass loss, and length change.

关键词： durability test freeze-thaw resistance polymer concrete residual compressive strength ASTM C666-15

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渤海海峡隧道支护结构耐久性分析

吴永胜,万飞,谭忠盛

《中国工程科学》 2013年第15卷第12期页码 67-72

摘要：

通过对海底隧道结构耐久性影响因素进行分析，并根据工程试验研究成果及设计施工技术经验，提出了渤海海峡隧道初期支护和二次衬砌结构耐久性的提高措施。对已成功修建的海底隧道耐久性设计参数进行分析整理，结合渤海海峡隧道的实际情况，采用工程类比法提出了渤海海峡隧道的耐久性设计参数，为渤海海峡隧道100年使用年限提供了有力的保障。

关键词：海底隧道支护结构耐久性设计参数

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基于PFM的B级钢侧架耐久性分析

李伟,李强,王平

《中国工程科学》 2011年第13卷第1期页码 56-61

摘要：

基于概率断裂力学对B级钢货车侧架的圆角细节进行了模拟耐久性试验研究，提出了一种新的通用当量初始缺陷尺寸分布的计算方法，建立了裂纹超越概率模型，从存活概率P, 应力水平σ, 裂纹形成时间t和经济维修极限a_e 4个角度评估了结构的损伤度, 并结合实测的应力谱预测了其经济寿命。结果表明，裂纹萌生时间能很好地服从三参数Weibull分布，求得的通用EIFS分布参数通过了K—S检验，拟合效果很好。裂纹超越概率模型可以对结构产生的耐久性损伤进行定量度量，预测的经济寿命随裂纹穿越概率的增加呈现增长的趋势，验证了新的计算方法和概率模型的合理有效性。

关键词：耐久性疲劳 B级钢裂纹

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A new systematic firefly algorithm for forecasting the durability of reinforced recycled aggregate concrete

Wafaa Mohamed SHABAN; Khalid ELBAZ; Mohamed AMIN; Ayat gamal ASHOUR

《结构与土木工程前沿（英文）》 2022年第16卷第3期页码 329-346 doi: 10.1007/s11709-022-0801-9

摘要： This study presents a new systematic algorithm to optimize the durability of reinforced recycled aggregate concrete. The proposed algorithm integrates machine learning with a new version of the firefly algorithm called chaotic based firefly algorithm (CFA) to evolve a rational and efficient predictive model. The CFA optimizer is augmented with chaotic maps and Lévy flight to improve the firefly performance in forecasting the chloride penetrability of strengthened recycled aggregate concrete (RAC). A comprehensive and credible database of distinctive chloride migration coefficient results is used to establish the developed algorithm. A dataset composite of nine effective parameters, including concrete components and fundamental characteristics of recycled aggregate (RA), is used as input to predict the migration coefficient of strengthened RAC as output. k-fold cross validation algorithm is utilized to validate the hybrid algorithm. Three numerical benchmark analyses are applied to prove the superiority and applicability of the CFA algorithm in predicting chloride penetrability. Results show that the developed CFA approach significantly outperforms the firefly algorithm on almost tested functions and demonstrates powerful prediction. In addition, the proposed strategy can be an active tool to recognize the contradictions in the experimental results and can be especially beneficial for assessing the chloride resistance of RAC.

关键词： chloride penetrability recycled aggregate concrete machine learning concrete components durability

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Accelerated life-time test of MEA durability under vehicle operating conditions in PEM fuel cell

Tian TIAN, Jianjun TANG, Wei GUO, Mu PAN

《能源前沿（英文）》 2017年第11卷第3期页码 326-333 doi: 10.1007/s11708-017-0489-z

摘要： In this paper, a novel accelerated test method was proposed to analyze the durability of MEA, considering the actual operation of the fuel cell vehicle. The proposed method includes 7 working conditions: open circuit voltage (OCV), idling, rated output, overload, idling-rated cycle, idling-overload cycle, and OCV-idling cycle. The experimental results indicate that the proposed method can effectively destroy the MEA in a short time (165 h). Moreover, the degradation mechanism of MEA was analyzed by measuring the polarization curve, CV, SEM and TEM. This paper may provide a new research direction for improving the durability of fuel cell.

关键词： polymer electrolyte membrane fuel cell accelerated life-time test load cycling test durability

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Long-term durability of onshore coated concrete —chloride ion and carbonation effects

Seyedhamed SADATI,Mehdi K. MORADLLO,Mohammad SHEKARCHI

《结构与土木工程前沿（英文）》 2016年第10卷第2期页码 150-161 doi: 10.1007/s11709-016-0341-2

摘要： Enhancing service life of reinforced concrete (RC) structures located in marine environments is an issue of great interest for design engineers. The present research addresses the effect of surface coatings on service life of onshore RC structures. Long-term performance of concrete samples up to 88 months of exposure at natural marine environment was investigated. Two onshore exposure conditions, including soil and atmosphere and different types of concrete coatings were studied. Carbonation rates of up to 0.5 and 1.5 mm/year were observed at the first 88 months of exposure for soil and atmospheric samples, respectively. Surface chloride ion build-up and variation in chloride ion diffusion were monitored with respect to time, and service life was estimated. Based on the obtained results it is proposed to use the aliphatic acrylic and polyurethane coatings for enhancing the service life of concrete structures in the investigated exposure conditions.

关键词： carbonation chloride ion corrosion service life surface coating

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Enhancing compressive strength and durability of self-compacting concrete modified with controlled-burnt

《结构与土木工程前沿（英文）》 2022年第16卷第2期页码 161-174 doi: 10.1007/s11709-021-0796-7

摘要： In sugar industries, the growing amount of sugarcane bagasse ash (SBA), a byproduct released after burning bagasse for producing electricity, is currently causing environmental pollution. The residual ash displays a pozzolanic potential; and hence, it has potential as a cement addictive. This study focuses on enhancing suitability of SBA through incorporating ground blast furnace slag (BFS) in manufacturing self-compacting concretes (SCCs). For this purpose, SBA was processed by burning at 700 °C for 1 h, before being ground to the cement fineness of 4010 cm²/g. SCC mixtures were prepared by changing the proportions of SBA and BFS (i.e., 10%, 20%, and 30%) in blended systems; and their performance was investigated. Test results showed that the presence of amorphous silica was detected for the processed SBA, revealing that the strength activity index was above 80%. The compressive strength of SCC containing SBA (without BFS) could reach 98%−127% of that of the control; combination of SBA and 30% BFS gets a similar strength to the control after 28 d. Regarding durability, the 10%SBA + 30%BFS mix exhibited the lowest risk of corrosion. Moreover, the joint use of SBA and BFS enhanced significantly the SCC’s sulfate resistance. Finally, a hyperbolic formula for interpolating the compressive strength of the SBA-based SCC was proposed and validated with error range estimated within ±10%.

关键词： sugarcane bagasse ash self-compacting concrete compressive strength sulfate resistance water absorption strength formula

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碱激发材料与普通硅酸盐水泥和混凝土的耐久性能比较 Review

王爱国, 郑毅, 张祖华, 刘开伟, 李燕, 石亮, 孙道胜

《工程（英文）》 2020年第6卷第6期页码 695-706 doi: 10.1016/j.eng.2019.08.019

摘要：

中国是世界上普通硅酸盐水泥（OPC）生产量和使用量最大的国家，基础设施建设的快速发展对混凝土材料提出了可持续发展的要求。碱激发材料（AAM）是一种新型节能环保建筑材料，具有广泛的应用前景。本文对比总结了AAM和OPC经硫酸盐侵蚀、酸侵蚀、碳化和氯离子渗透后的耐久性能，阐述了因硅铝质原材料不同和碱激发产物不同，导致AAM耐久性能表现出巨大差异的关系，并根据硅铝质原材料的钙（Ca）含量的高低，对比分析了无钙、低钙、高钙三种体系的AAM的性能劣化机理。尽管目前不同的研究对AAM的耐久性能和长期稳定性存在一定争议，并引起了相当的关注，但总体而言，AAM较OPC表现出了更好的耐久性能。

关键词：碱激发材料地聚合物耐久性能普通硅酸盐水泥劣化机理

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Coupled diffusion of chloride and other ions in saturated concrete

Nattapong DAMRONGWIRIYANUPAP, Linyuan LI, Yunping XI

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 267-277 doi: 10.1007/s11709-011-0112-z

摘要： Corrosion of reinforcing steel due to chloride ions is one of the severe deterioration problems in long-term performance of reinforced concrete structures. The deterioration process is frequently found in marine concrete structures, highway pavements, and bridges exposed to deicing salts. The diffusion of chloride ions is associated and strongly affected by other ions in the pore solution in concrete. In this paper, chloride penetration into concrete structures was mathematically characterized by the Nernst-Planck equation which considered not only diffusion mechanism of the chloride ions but also ionic interaction among other ions coming from externally applied deicers and within the Portland cement paste. Electroneutrality was used to determine the electrostatic potential induced by the ionic interaction. The material models of chloride binding capacity and chloride diffusion coefficient were incorporated in the governing equations. The governing equations were solved by using finite element method. A numerical example was used to illustrate the coupling effect of multi-ionic interactions and the effect of influential parameters. The numerical results obtained from the present model agreed very well with available test data.

关键词： diffusion chloride concrete Nernst-Planck equation durability

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关于水泥混凝土发展方向的几点认识

唐明述

《中国工程科学》 2002年第4卷第1期页码 41-46

摘要：

根据在加拿大观察到的重大混凝土工程破坏实例，反复强调我国在基建工程中必须十分重视耐久性问题。为实现可持续发展，应逐步将水泥工业转变为"绿色胶凝材料工业"。阐述了根据混凝土的技术进步重新审议水泥的标准与组成。最后建议把水泥的生产、流通与使用协调起来，以获得更大的经济和社会效益。

关键词：水泥混凝土耐久性分类混合材标准

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Concept and requirements of sustainable development in bridge engineering

Yaojun GE, Haifan XIANG

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 432-450 doi: 10.1007/s11709-011-0126-6

摘要： The concept of sustainability is described in this paper using a single sustainable principle, two goals of sustainable development, three dimensions of sustainable engineering, four sustainable requirements and five phases of sustainable construction. Four sustainable requirements and their practice in China are discussed in particular. The safe reliability of bridges is first compared with the events of bridge failure in China and in the rest of the world and followed by structural durability, including the cracking of concrete cable-stayed bridges, deflection of concrete girder bridges and fatigue cracks of orthotropic steel decks. With respect to functional adaptability, lateral wind action on vehicles and its improvement are introduced regarding a sea-crossing bridge located in a typhoon-prone area. The Chinese practice of using two double main span suspension bridges and a twin parallel deck cable-stayed bridge is presented in discussing the final sustainable requirement: capacity extensibility.

关键词： sustainable engineering safe reliability structural durability functional adaptability capacity extensibility

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现代混凝土结构环境模拟试验室技术

李云峰,吴胜兴

《中国工程科学》 2005年第7卷第2期页码 81-85

摘要：

为了在试验室人工模拟环境下进行混凝土早期特性、裂缝控制及耐久性的试验，需对混凝土结构环境模拟试验室技术进行研究。分析了环境模拟技术在诸多领域的成功应用，认为建设混凝土环境试验室是可行的。通过研究混凝土结构的环境模拟、试验设计、耦合环境的实现以及特种设备仪器的应用等关键技术，提出大型多功能自动控制混凝土环境试验室的建设方案，合理确定试验室的布局、功能、技术性能指标，并探讨了人工气候环境试验室设备、仪器的优化配置，为下一步混凝土耐久性、裂缝控制的环境试验研究奠定了基础。

关键词：凝土结构环境试验耐久性裂缝控制人工气候