Microstructural Investigation of Reinforced Concrete Exposed to Cyclic Wetting and Drying

Abstract

Concrete which placed in an aggressive environment has a great chance to suffer from damage especially for concrete put in the marine environment. In this situation, damage process in concrete is mainly caused by chloride ingress. The chloride penetrates into the concrete by various mechanisms. For concrete submerged in seawater, the chloride solution penetrates into the concrete trough diffusion mechanism and cause damage over the time. However, in real life, reinforced concrete structure mostly placed in the partially saturated area and subjected to the repeated actions of the wetting and drying cycle. This condition makes the concrete structures more vulnerable to corrosion than structures in a fully saturated condition. Therefore, this study investigates the changes in concrete microstructures condition due to repeated actions of wetting and drying. The samples were exposed by 5% NaCl solution through the different configuration of wet and dry duration. The microstructural condition was observed by several methods such as XRF, SEM and EDX analysis. Major constituent phases of concrete and the differences in their distribution due to different duration of wet and dry were observed in this study. Finally, from the investigation, it was found that there were noticeable differences in chloride and magnesium percentage in the samples. This result acts as evidence that the duration of wet and dry can affect the formation of particular compounds such as chloroaluminate, quartz, brucite, and dolomite in the samples which plays roles in the damage process of concrete.