For the sea-sand concrete, the chloride ions should be uniformly distributed after casting. However, the chlorides are redistributed after being exposed to the carbonation environment, which can significantly reduce the effective service life of sea-sand concrete. In this study, a new mathematical model, coupling several parameters, including the changes in carbonation degree, moisture transport and release of bound chlorides under the carbonation, were firstly proposed to accurately predict the phenomenon of chloride redistribution in chloride blended and carbonated concrete. It was found that experimental results of chloride redistribution were fitted well with the proposed model. The rebar corrosion in this case was initiated by the excess of chloride ions rather than carbonation or oxygen diffusion. The ratio of Cl-/[OH-] is a key parameter in prediction of corrosion initiation. Next, the model was extended to predict the effective service time of newly-built and existed sea-sand concrete structures in practical engineering. The relationships between affecting parameters, e.g., chloride and moisture diffusion coefficient, carbonation rate and initial chlorides, on the effective service time exposed to carbonation effect were analyzed. Some practical suggestions were put forward for extending the service time of new-built sea-sand concrete structures to the designed time. It is expected the results of this study can be used for the basis of understanding the durability performance of sea-sand concrete subjected to carbonation environment.