For a very long time, huge amounts of money and natural resources have been spent on repairs and rehabilitation of concrete structures in severe marine environments, and this is primarily due to premature corrosion of embedded reinforcement. Therefore, a probability-based approach to the durability design is very important. In this paper, an advanced procedure for durability design and concrete quality control during concrete construction has been presented through some tests including chloride diffusivity and cover thickness of the concrete.
Chloride ingress is one of the most important factors in the corrosion process of concrete reinforcement. Especially for off-shore and marine constructions the exposure to chlorides from sea water and marine air plays an important role. The ingress of chloride ions into the pores of the concrete is caused by diffusion through the pores if they are filled with water or capillary suction if the pores are empty. When the chloride ions reach the reinforcement, the passivating oxide layer may be depassivated, which initiates the local corrosion of the reinforcement (Page CL, 1975; Broomfield JP, 1997). The chlorides in the concrete either come from the components of the fresh mix or from external contamination. The chlorides that contribute to the corrosion risk of the reinforced concrete structures are the free chlorides in the pore water and the water soluble salts (Salt of Friedel) that act as a source of free chlorides. Thus, the importance of predicting the corrosion free life of concrete structures exposed to a marine environment has been emphasized to ensure the safety of the structures against chloride-induced corrosion of reinforcement. The rate of chloride transport and the resistance of steel to corrosion are primarily required to model the corrosion free service life.
