A Study on Estimation for Chloride Diffusivity in Cracked Concrete in Harbor Structures through Field Survey

Chloride attack in concrete structure is one of the most deterioration phenomena so lots of researches are focused on this field such as modeling and analysis of chloride behavior including material, design, and construction. However, one of the major object is to simulate the chloride behavior of existing structures and it is also important to evaluate it through the field survey. Generally researches for chloride behavior are focused on sound concrete but it is rarely carried out to evaluate and verify that in cracked concrete. Cracks in early-aged concrete, however, may occur inevitably through the mechanism such as cement hydration and shrinkage and they can be the main routes for deteriorating agent, which induce local steel corrosion. In this study, field survey for concrete structures exposed to sea water is performed and apparent diffusivities of chloride ion in sound concrete is evaluated. Furthermore, those in cracked concrete with 0.1, 0.2, and 0.3 mm crack width are also experimentally evaluated. The evaluated diffusivities in cracked concrete are expressed in terms of crack width and those in sound concrete and service life prediction for target structure is carried out through the relationship between them. Additionally, Utilizing the diffusion factor for crack effect from domestic specification, service life prediction is performed for the same structure, and comparison between the results from the derived relationship and those from domestic specification is also carried out. Through this study, chloride diffusivity with crack effect in domestic specification is evaluated to underestimated the chloride behavior and it is currently necessary to derive the quantitative crack effect through comprehensive field survey.