A statistical treatment has been applied to cover depths from field test for three existing marine structures. The electromagnetic covermeter testing method is used to measure the cover depths of existing marine concrete structures. The standard derivation of the testing values is very large, the mean value is very close to the design value, and the testing values of cover depths follow a normal probability distribution function. Finally, effect of variation of cover depths on the service life of marine structures is discussed.
Reinforced concrete structures will deteriorate and damage because of the natural environment and long-time usage. The durability of structures is one of the important objectives for reliability of engineering structure. Concrete normally provides a high degree of protection to the reinforcing steel against corrosion, by an oxide passive film generated in a highly alkaline environment. Prediction of time to corrosion cracking is a key element in evaluating the service life of reinforced concrete (RC) structures(Ahmad, 2003). This is because the appearance of the first corrosion crack is usually used to define the end of functional service life where rehabilitation of a corroding structural element is required (Maaddawy and Soudki, 2007). Once reinforcement corrosion is initiated, it progresses almost at a steady rate and shortens the service life of the structure, by causing surface cracking and subsequently spalling of the cover concrete due to expansion of the corroding steel. As same as previous investigation (Kwon, Na, Park, Jung, 2009; Martin-Perez, Zibara, Hooton and Thomas, 2000), service life in this study has been defined as the time required for the chloride concentration at the reinforcement to reach the critical chloride level. Based on Fick's second law of diffusion, some approaches to estimate the service life of a concrete structure in marine environment, have been developed.
