The Corrosion Process in Reinforced Concrete

Modern structures in aggressive environments are increasingly being engineered to achieve a life expectancy based on the impenetrability of the concrete to chloride ions. These predictions are normally based on Fick&s;s laws of diffusion even though it is commonly known that this is an over simplification of the transport situation in concrete. There have been significant attempts to improve the actual life of a reinforced concrete structure by changing the material properties of both the reinforcement and concrete. As the exposure time increases, the rate of corrosion reduces, as the oxide layer provides a barrier to ionic, atomic and gaseous transport. An experiment was undertaken where the specimen size was varied in the same experimental procedure. It was found with exactly the same experimental conditions and procedures that reinforced concrete samples with 1 cm, 10 cm and 100 cm lengths required very different chloride concentrations to initiate corrosion.