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

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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 *** mechanical properties of the laboratory dam concrete,whether cured in natural or standard environments,continued to improve over ***,the laboratory dam concrete exhibited good resistance to diffusion and a refined microstructure after 17 ***,curing and long-term exposure to the local natural environment reduced the frost *** 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 *** obvious interfacial transition zones were observed in the microstructure owing to the longterm pozzolanic *** 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 *** 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 *** 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 ***-term exposure to an actual service environment may lead to microstructural degradation of the concrete ***,the retained long-term dam concrete samples need to be further researched to

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

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

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 *** structural combination char-acteristics of typical long-life asphalt pavement in Shandong Province and their popularization and application are *** application effect of combined base long-life asphalt pavement,which has been widely promoted,is *** 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 *** S1,S2,and S3 present information about full-depth asphalt *** S4 describes combined base asphalt *** 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 *** 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 *** deflection index was stable without growth,and the IRI was also relatively stable following the opening to *** rutting depth un-derwent a slight cumulative increase within 8 years of opening,and then *** average rutting depth over the 17-year period was less than 15 ***,S1–S4 meet the design standards required for use as long-life *** 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

Curling of New Concrete Pavement and long-term performance

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Journal of Civil Engineering and Architecture 2012年第2期6卷 121-130页

作者： Daba S. Gedafa M. Hossain Z. Q. Siddique K. Fredrichs D. Meggers University of North Dakota 243 Centennial Dr Stop 8115 Grand Forks ND 58202-8115 USA Department of Civil Engineering 2118 Fiedler Hall Kansas State University Manhattan KS 66506 USA ARCAD1S LNW 420 Columbia Drive Suite 110 West Palm Beach FL 33409 USA FHWA Kansas Division 6111 SW 29th St. Topeka KS 66614 USA Bureau of Materials ＆ Research Kansas Department of Transportation 2300 Van Buren Topeka KS 66611 USA

Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.

关键词： Curling HIPERPAVII long-term performance MEPDG.

Energy and long-term hygrothermal performance of building enclosures based on dynamic environmental simulation test

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Engineering Sciences 2010年第1期8卷 92-96页

作者： Shi Xing Key Laboratory of Urban and Architectural Heritage Conservation of MOE Southeast University Nanjing 210096 China

Dynamic environmental testing is an effective means to study the energy and long-term hygrothermal performance of building enclosures. Southeast University is designing and building a large-scale dynamic environment simulation testing facility. It can simuhaneously and dynamically simulate temperature, relative humidity, infrared solar radiation, UV radiation, and precipitation. A transformation is needed to predict the energy and long-term hygrothermal performance of building enclosures under real service conditions using data obtained from accelerated tests.

关键词： environmental simulation hygrothermal performance long-term performance heat box environmental acceleration

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 *** 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 *** effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and *** study illustrates the influence of ageing and repeated seismic shaking on lining deformation,crack development,and the modal characteristics of the intact and degrading *** 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 *** different tunnel embedment depths are comparatively *** 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

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 *** are planted with select species,which ensure consistent cover and performance over *** research presented herein is part of a systematic re-evaluation of EGR technology since the German industry ***: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 ***: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 *** soil variables are inter-related,as shallow acidic substrates create unfavourable conditions for decomposition and thereby the accumulation of *** variables correlated with EGR vegetation,suggesting a trend of simplified species composition over ***,Corg had a negative relationship with cover and species diversity of most life forms;only Sedum species had positive associations with ***: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