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Research on Flexural RC Components Exposed to Marine Environments: Durability and Life Prediction

Author: WuQingLing
Tutor: YuHongFa
School: Nanjing University of Aeronautics and Astronautics
Course: Road and Railway Engineering
Keywords: Marine Concrete The marine environment Tidal zone Underwater District Salt spray area Salt carbonization zone Durability Life Chloride ion binding capacity Diffusion coefficient Relative dynamic elastic modulus Damage Carrying capacity Steel corrosion rate Reliability Life Prediction
CLC: TU375
Type: PhD thesis
Year: 2010
Downloads: 261
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Abstract

Countries in the world are faced with poor durability of marine concrete serious problem, the government had to pay a lot of \and lifetime prediction method, has important social significance and engineering application value. In this paper, marine areas under environmental corrosion of concrete and corroded concrete structures as the research object, through our coastal marine concrete durability test fieldwork analysis and research, focusing on marine splash zone, underwater areas, tidal zones and salt spray areas such as the durability of concrete damage failure process and its laws, in-depth analysis of the damage marine concrete degradation processes and degradation mechanisms, including the chloride ion diffusion law, concrete changes in the relative dynamic modulus of elasticity of concrete deterioration injury law, concrete corrosion in seawater , such as the role of wet and dry cycle durability under evaluation, and ultimately establish a marine environment corroded reinforced concrete durability prediction model research for marine concrete structural engineering assessment of the safety and durability of the more important to provide a basis for the final realize the durability of marine concrete structures designed to lay the foundation. The main research contents and results are as follows: The first chapter summarizes the marine concrete durability and service life prediction method of significance and research trends and research, pointed out the problems in the current study, determined on the basis of of this research program and research. The second chapter begins for chloride ions on the dangers of marine concrete structures analyzed marine concrete or marine concrete structures in coastal areas in South and North durability and service life, and then to explore the marine concrete reinforcement corrosion in the basic conditions , mechanism and influencing factors; Finally, we discuss marine concrete area in the atmosphere, underwater areas, salt spray zone, tidal zone and the splash zone degradation mechanisms; thus for the establishment and use of the environment to adapt to life prediction of marine concrete model laid the foundation. Chapter preliminary preferably several mixing mineral admixtures concrete mix, experimental study of ordinary concrete, high performance concrete, concrete and other mineral admixture preparation and basic properties. In order to study concrete and reinforced concrete structures in the marine underwater area, tidal zone, splash zone, atmospheric area and splash zone and other marine areas in the durability of the similarities and differences between the environment, focusing on the design of marine concrete durability tests and field exposure laboratory simulation tests, including: (a) concrete material in the marine environment and the indoor room temperature exposure test seawater immersion corrosion test; (2) of reinforced concrete structures in the marine environment and indoor exposure test, accelerated test simulated marine environment. Chapter simulated marine underwater areas, tidal areas, salt spray and salt spray carbonization zone area, carried out in the laboratory of concrete materials and corrosion damage of reinforced concrete members comparison test, combined with on-site marine environment reinforced concrete nondestructive testing and comparative analysis to determine the concrete relative dynamic elastic modulus and mass loss rate, while observing the appearance of the specimen peeling Representations studied marine concrete injury law and degradation characteristics; Finally, we discuss concrete materials and concrete structures Injury contrast. Chapter exposure mainly in the field and laboratory simulation test based on concrete specimens were measured at different depths of the total chlorine ion concentration and free chlorine concentration, in-depth study of ordinary concrete, high-performance concrete, mixed with mineral additive Concrete in the marine atmosphere zone, underwater area, tidal zone and splash zone environments such as marine areas of concrete Cl-proliferation laws, and marine areas for different environments and different types of concrete, discusses the marine concrete chloride ion diffusion characteristics . Chapter VI to corroded reinforced concrete members as the research object, according to the scene of the ocean regional environmental law and natural exposure laboratory accelerated corrosion method, the corrosion of reinforced concrete bending bearing capacity test results and failure modes for a detailed analysis and discussion; while establishing a marine environment in the region based on steel corrosion rate analysis model discussed dosage of mineral admixtures and concrete strength on steel corrosion rate of given surface reinforcement steel corrosion rate and the relationship between the chloride ion content; final consolidated Consider steel corrosion rate on the performance of reinforced concrete and reinforced with concrete bonding performance, the current structure is proposed based on design specifications corroded reinforced concrete flexural capacity assessment model, and the results were compared with experimental verification, the results show that the proposed bearing capacity of corroded reinforced concrete assessment model calculations and experimental results are in good agreement, proof of assessment model established in this paper has a high value in use, the model can be applied to the actual marine concrete structural engineering. Chapter VII based on improved Tuutti model to analyze the structure of marine concrete failure process and the definition of life, studied based on chloride ion corrosion of marine invasive concrete life of two phases prediction method, the two together shall be final life. (A) First stage: Consider the concrete in the marine environment, the process of using Cl-chloride ion diffusion coefficients and their time-dependent chloride ion binding capacity, the critical chloride ion concentration, the initial chloride ion concentration inside the concrete and concrete chloride ion diffusion performance deterioration effect coefficient, the paper cited an improved assessment of the first phase of life calculation model life. (2) The second stage: assumed life of steel corrosion rate of 5% of the elapsed time, during which the rebar corrosion caused due to bending load capacity decreased, resulting in the flexural capacity of corroded reinforced concrete moment is less than the design value and failure. When the steel corrosion rate of more than 5%, the bond strength of reinforced concrete and substantial reduction in the durability of concrete structures fail, that is the second phase of marine concrete durability of end of life signs. Finally, according to uniform standards for reliability design of concrete structures, based on reliability theory initially proposed marine concrete corrosion life prediction model, and pointed out that the reliability and validity of the model problem. The results show that both in the marine tidal zone, splash zone or underwater area, F20C70 life of concrete structures are larger than other concrete, the basic 100a above. Chapter VIII summarizes the main work and conclusions put forward suggestions for further research.

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