This paper evaluated service life in a RC continuos beam with 2 spans considering loading condition, cold joint, and substitution ratio of GGBFS. Based on the previous test results for 91 and 365 days, changing ratio of diffusion coefficients with applied stress are normalized considering substitution of GGBFS and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted. The reduction of service life with cold joint and loading condition should be considered in maintenance even if GGBFS which shows excellent resistance to chloride ingress is used for the RC structures.