ABSTRACT
In engineering construction, combined with the advantages between tensile resistance of steel and compressive resistance of concrete, RC structures have become the most widely used forms. Also, it must satisfy the requirements for safety, applicability and durability. Durability refers to the ability that component can keep applicability and security during design working life under certain circumstances and conditions of maintenance and use. In using process, due to the characteristics of material itself and application environment, the material suffers various corrosion and damage leading to the reduction of durability and reliability. So the actual life of structure is shorter than design life which causes great economic loss (Jin & Zhao 2002).
