Abstract: A cellular automata (CA) model of chloride ion diffusion in concrete was built based on Fick’s second law to accurately simulate the chloride ion erosion in concrete box girder, obtain the concentration of chloride ion at arbitrary position at any time in cross section, and to predict the durability life of the structure. The effects of material and age on the diffusion effect of chloride ion were taken into consideration. MATLAB calculation program was compiled based on the built CA model. Results of the study demonstrated that compared with the analytical solution and test value of chloride ion concentration, the result of the built CA model is of higher accuracy in simulating chloride ion diffusion in concrete box girder. Chloride ions diffuse in different laws varying with the form of chamfering sections, and the time required for critical concentration of chloride ion for steel corrosion is different. In addition, the model is proved to effectively predict the durability of concrete through comparison with the analytic solution of life prediction. The durability of the studied concrete box girder is around 51 years.

Key words: concrete box girder, life prediction, chloride ion diffusion, cellular automata model, numerical analysis