Chloride Transport In Concrete And Steel Corrosion Law Under Carbonation And Loading Effect

Under the joint erosion of chloride and carbon dioxide, durability of concrete structures in marine environment is deteriorated seriously. Concrete carbonation and chloride attack have interaction effect. In addition, loading effect has an impact for the transport of chloride and carbon dioxide in concrete at the same time. Researches on chloride transport in concrete, as well as the steel corrosion law under carbonation and loading effect play an important role in accurately predicting the service life of concrete structures in marine environment. While in this main line, the main research work is as follows:(1) By designing a variety of wet and dry cycling tests to simulate the marine environment, the influence of concrete carbonation on chloride transport and the interaction effect of carbonation and chloride attack for ordinary concrete as well as fly ash and slag concrete were analyzed. Considering the influence of carbonation, chloride transport model under wet and dry cycles was proposed, in which the parameters were determined. A corresponding program was programed to solve the chloride transport model. Model calculation results and experimental results were compared to verify the reliability of the model.(2) Based on the interaction effect of concrete carbonation and chloride attack, the chloride immersion and accelerated carbonation cycling tests were carried out for concrete beam specimens subjected to different load levels to analyze the impact of loading effect on concrete carbonation and chloride attack. By proposing a model considering the influence of loading effect on chloride diffusion coefficient, and determining the parameters in model, chloride transport model considering the influence of carbonation and loading effect under wet and dry cycles was established. Model calculation results was consistent with experimental results, and it can be used to predict the chloride transport in concrete considering the influence of carbonation and loading effect under wet and dry cycles.(3) By using half-cell potential method and linear polarization method to monitor corrosion potential and corrosion current density of steel in concrete continuously, the development of steel corrosion under the combined effect of load, carbonation and chloride attack was analyzed. The accuracy of electrochemical methods was verified by measuring the rate of steel corrosion. The surface corrosion morphology of corroded steel under the chloride immersion and accelerated carbonation cycling tests were analyzed together with the compositions and microstructure of corrosion products. The applicability of simulating real steel corrosion law in marine environment by using chloride immersion and accelerated carbonation cycling test was discussed.