Monitoring concrete performance under simulated and natural chloride environments
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Deterioration of reinforced concrete structures caused by chloride-induced corrosion is well-known in the construction industry, but it is still difficult to evaluate the performance of the structures due to various exposure conditions and characteristics of concrete, especially containing supplementary cementitious materials (SCMs). In this study, comprehensive assessments of both chloride transport and corrosion initiation/propagation were, therefore, performed to study the performance of concrete subjected to a chloride environment. Chloride transport in concrete was assessed using the migration/diffusion coefficient, porosity/degree of saturation and electrical resistance/resistivity. The electrical resistivity of the concrete was used as a single 'performance' factor. In addition to chloride transport, the condition of steel embedded in concrete was monitored using electrochemical methods. The electrical resistance/resistivity of concrete was monitored over a period of 382 days and then analysed using a normalisation technique to identify the chloride transport and corrosion process. In addition, the condition of concrete slabs (18 years old) retrieved from the Dornoch Firth marine exposure site (representing XS3 environmental exposure class) were evaluated using the same procedures conducted in the laboratory. In monitoring the electrical resistance/resistivity, the activation energy was calculated to reflect the environmental conditions, in this instance diurnal and annual temperature variation. Finally, for time to corrosion initiation, the ClinConc model was combined with two new environmental factors and during corrosion propagation, the polarisation resistance was estimated using a fitting method.