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long-term performance and Microstructural Characterization of Dam Concrete in the Three Gorges Project

Engineering 2024年第2期33卷 237-262页

作者： Chen Lyu Cheng Yu Chao Lu Li Pan Wenwei Li Jiaping Liu School of Materials Science and Engineering Southeast UniversityNanjing 211189China State Key Laboratory of High performance Civil Engineering Materials Sobute New Materials Co.Ltd.Nanjing 211103China China Three Gorges Corporation Wuhan 430010China

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 micro structures consisting of large quantities of homogeneous calcium(alumino)silicate hydrate(C-(A)-S-H)gels and a few crystals.No obvious interfacial transition zones were observed in the microstructure owing to the longterm 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

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

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long-term performance of recycled asphalt mixtures containing high RAP and RAS

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Journal of Road Engineering 2024年第1期4卷 36-53页

作者： Jiangmiao Yu Zengyao Lin Guilian Zou Huayang Yu Zhen Leng Yuan Zhang School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 510641China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina State Key Laboratory of Subtropical Building and Urban Science South China University of TechnologyGuangzhou 510640China

The application of reclaimed asphalt pavement(RAP)and reclaimed asphalt shingles(RAS)on asphalt pavement can reduce the asphalt paving cost,conserve energy and protect the environment.However,the use of high contents of RAP and RAS in asphalt pavement may lead to durability issues,especially the fatigue cracking and thermal cracking.It is necessary to conduct a series of analyses on asphalt mixtures containing high RAP and RAS,and seek methods to enhance their long-term performance.This paper provides a comprehensive over-view of the long-term performance of recycled asphalt mixtures containing high contents of RAP and RAS.The findings in this research show that rutting resistance of high recycled asphalt mixtures is not a concern,whereas their resistance to fatigue and thermal cracking is not conclusive.Recycling agents can be used to improve the thermal cracking resistance of high recycled asphalt mixtures.An optimum decision on recycling agents will improve the durability properties of high recycled asphalt mixtures.It is recommended that to use a balanced mixture design approach with testing of the blended asphalt binders will provide better understanding of long-term performance of recycled asphalt mixtures containing high RAP and RAS.

关键词： Recycled asphalt mixture Recycling agents long-term performance Cracking

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Technical development and long-term performance observations of long-life asphalt pavement: A case study of Shandong Province

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Journal of Road Engineering 2022年第4期2卷 369-389页

作者： Lin Wang Jincheng Wei Wenjuan Wu Xiaomeng Zhang Xizhong Xu Xiangpeng Yan Shandong Transportation Institute Jinan 250102China Key Laboratory of Expressway Maintenance Technology Ministry of Transport Jinan 250102China

Based on the investigation of long-life asphalt pavement at home and abroad,the development of long-life asphalt pavement technology in Shandong Province,China is reviewed in this paper.The structural combination char-acteristics of typical long-life asphalt pavement in Shandong Province and their popularization and application are introduced.The application effect of combined base long-life asphalt pavement,which has been widely promoted,is evaluated.At the same time,taking the Binda perpetual pavement test road in Shandong Province as an example,the dynamic response and long-term performance evolution of long-life asphalt pavement are analyzed over a period of more than 17 years.Sections S1,S2,and S3 present information about full-depth asphalt pavement.Section S4 describes combined base asphalt pavement.The results show that the maximum strain of S1–S4 is within the endurance strain limit.S1,S2,S3 and S4 are all expected to be long-life asphalt pavements.In the current study,Sections S1–S4 were maintained in good condition during a service period of more than 17 years with no structural cracks and good deflection,rutting,and IRI indexes.The deflection index was stable without growth,and the IRI was also relatively stable following the opening to traffic.The rutting depth un-derwent a slight cumulative increase within 8 years of opening,and then stabilized.The average rutting depth over the 17-year period was less than 15 mm.Therefore,S1–S4 meet the design standards required for use as long-life pavements.From the perspectives of resource saving,energy saving,and emission reduction and service performance,full-depth asphalt pavement can be considered to represent a new generation of green and durable pavement structures with great future promotion potential.

关键词： long-life asphalt pavement Dynamic response Strain Deflection long-term performance

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long-term performance of Moderate Heat Portland Cement with Double-expansive Sources

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Journal of Wuhan University of Technology(Materials Science) 2007年第1期22卷 35-39页

作者：叶青 College of Architecture and Civil Engineering Zhejiang University of Technology

The long-term performance of moderate heat Portland cement with double-expansive sources （DE cement） in the system of high MgO clinker and gypsum was studied by XRD, SEM/EDAX and test methods for strength and expansion of cement. Results indicate that the periclase particle, whose size was 5-7.5μm in DE cement clinker containing 4.8 % MgO, existed individually. The periclase hydration in hardened DE cement paste started at about 60 days and completed up to 2 000 days, and ettringite in the paste was stable from 3 days to 2 000 days. Under the conditions of 4.5%-5.0 % MgO in clinker and 2.8%-3.4 %SO3 in cement, ettringite expansion and brucite expansion in DE cement paste had a continuity, entirety and stability. At the ages of 90, 365,730 and 2 000 days the expansion of the paste reached 0.07%-0.11%, 0.16%-0.21%, 0.21%-0.27 %, and 0.29%-0.38%, respectively. The results suggest that by using this cement in mass concrete it may compensate its temperature shrinkage and autogenous shrinkage to some extent.

关键词： brucite ettringite expansion long-term performance moderate heat Portland cement

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A numerical case study on the long-term seismic assessment of reinforced concrete tunnels in corrosive environments

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 551-572页

作者： Maria Antoniou Antonios Mantakas Nikolaos Nikitas Raul Fuentes ETH Zurich ZurichSwitzerland National Technical University of Athens AthensGreece University of Leeds LeedsUK RWTH Aachen University AachenGermany

The paper investigates the long-term seismic behaviour of an underground reinforced concrete(RC)metro tunnel in Santiago,Chile,considering the combined effects of chloride-induced corrosion and cumulative,low-amplitude seismic shaking on the structure’s performance.The soil-tunnel response is evaluated with the aid of transient,nonlinear finite element analysis using a two-dimensional(2D)plane strain numerical model that adopts advanced nonlinear models for the simulation of soil and concrete plasticity and the dynamic stiffness behaviour.The effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and strength.The study illustrates the influence of ageing and repeated seismic shaking on lining deformation,crack development,and the modal characteristics of the intact and degrading systems.The results indicate that multiple lowamplitude events drive the non-degrading RC tunnel beyond its elastic regime without significant structural response consequences.A noticeable impact of corrosion deterioration on the structure’s seismic performance is revealed,increasing with the number and intensity of earthquake events.Two different tunnel embedment depths are comparatively assessed.The analyses demonstrate larger coseismic section convergence in the case of the deeper tunnel,yet a less pronounced effect of ageing and successive seismic loading compared to the shallow section,which is evident in the RC lining cracks at the end of shaking.

关键词： Tunnels Reinforcement corrosion Ageing Earthquakes Numerical modelling long-term performance Concrete cracking behaviour

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Vegetation composition of old extensive green roofs(from 1980s Germany)

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Ecological Processes 2014年第1期3卷 225-235页

作者： Christine E Thuring Nigel Dunnett Department of Landscape Floor 9The Arts TowerWestern BankSheffieldSouth Yorkshire S102TNUK

Introduction:Since their development in the late 1970s in Germany,extensive green roofs(EGR)have become increasingly popular as mitigation tools for urban environmental issues around the world.EGRs are planted with select species,which ensure consistent cover and performance over time.This research presented herein is part of a systematic re-evaluation of EGR technology since the German industry began.Methods:Given the opportunity to access a small sample of old EGRs installed over 20 years ago in south-west Germany,this research surveyed the vegetation and substrate with an interest in describing these parameters with time-through-space substitution.Results:Similar to previous studies,this preliminary work found correlations between roof age with vegetation(cover abundance and species diversity)and substrate properties(e.g.,depth,organic content,pH,and nutrients).Roof age had positive relationship with soil organic content(Corg),and negative relationships with substrate depth and soil pH.These soil variables are inter-related,as shallow acidic substrates create unfavourable conditions for decomposition and thereby the accumulation of duff.Substrate variables correlated with EGR vegetation,suggesting a trend of simplified species composition over time.Indeed,Corg had a negative relationship with cover and species diversity of most life forms;only Sedum species had positive associations with Corg.Conclusions:Considering the dynamics associated with shallow mineral substrates,and the greater floristic diversity of younger roofs,simple Sedum-based vegetation may represent a steady state for conventional EGRs.

关键词： Biodiversity Extensive green roofs Germany long-term performance Plant life forms Sedum Species diversity Substrate depth

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