| The durability of reinforced concrete structures under chloride erosionenvironment has attracted much more attention from scholars in the field of civilengineering. As a key factor for chloride ions caused corrosion of steel and concretecover off, it is crucial to study chloride ions transport processes and mechanism,establish transport models under different environment for the issues of durability ofreinforced concrete. therefore, based on the transmission mechanism of chloride ionsin the concrete, the transmission model of chloride ions in water-saturatedenvironment and wet-dry environment are established to analyze chloride ionstransport processes in the underwater zone and the tidal zone (including the splashzone)under the marine environment. Specially, the transport model of chloride ionsin concrete coupling with load are established. At the same time, in order to digchloride ion transport mechanism, the influence of Interfacial Transition Zone andthe distribution of micro-cracks on chloride ions transport are studied from theperspective of meso-structure of concrete. The content includes:(1) First, the driving forces, transmission mechanics and description equationsof the mainly transmission of chloride ions in concrete are analysed based on thetheories of electrochemistry, including convection, diffusion, capillarity,electro-migration, etc. The chloride ions transport models are established to describechloride ions transmission in different marine environment based on complexcoupling of the above one or several transmission.(2) According to the transmission mechanism of chloride ion in water-saturatedenvironment, improve the chloride ions transport model which non-steady statediffusion equation is the core. Considering temperature, age, saturation, damage andother factors on the chloride diffusion process, consistent results are obtainedthrough the analysis of the model and compared with the experimental results. Underlaboratory and the exposure experiments conditions, the applicability of the chlorideions transport model in the saturated state is verified. The results show that thesimulation results are closer to the experimental value, and get higher calculationaccuracy.(3) Based on chloride ion transport mechanism in the tidal zone and the splashzone of the marine environment, the chloride ions convection-diffusion transportmodel is established. As saturation s is the coupling variable, the chloride ionstransfer process is described by the physical field coupled the pore solution capillary migration and chloride ions diffusion. The transport model for concrete in thewet-dry environment is calculated and analysed by COMSOL finite element software,which results are agree well with the experimental data. At the same time, parametersensitivity analysis shows that two important parameters of the model: the initialsaturation of pore s0and the dry-wet cycling regime are the two main factorsaffecting the transportation of chloride ions in unsaturated state.(4) As the concrete in the marine environment suffers the combined effect of theload and the erosion of chloride, the transport model of chloride ions coupling withthe load are established, in which bulk strain and porosity are the coupling variables.According to the model, chloride ions intrusion process simulation is carried outabout a plain concrete beam bend experiment, chloride ions distribution is obtainedunder different load levels, eventually simulation values show good agreement withthe experimental results.(5) From the perspective of meso-structure of concrete, especially the interfacialtransition zone, the chloride ions transport properties are analysed. At the same time,the relation between micro-cracks density, length, micro-crack orientation and thechloride ions transport properties are studied. by means of simple two-dimensionalcrack network model, the micro-crack length, orientation and average spacing areresearched to find how they influence the chloride ions transport properties. |
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