Carbonation of reinforced concrete is a potential durability issue for vehicular tunnels. This is particularly the case where elevated carbon dioxide concentrations exist and when the design life is 100 years or more. The process of carbonation can result in loss of passive protection to embedded steel reinforcement and initiation of corrosion._x000D_
Therefore, tunnel design needs to consider the potential for carbonation on internal surfaces and how design life can be achieved in severe environments._x000D_
This paper examines methods for predicting carbonation and how deterioration can be mitigated through appropriate concrete mix design and construction practices.