Decreased corrosion initiation time of steel in concrete due to reinforcing bar obstruction of diffusional flow

When chlorides migrate into concrete by diffusion, reinforcing bars act as a barrier to transport, causing a more rapid increase in concentration at the leading face of the reinforcing bar than would be expected from simple one dimensional predictions. The time interval to reach the critical concentration to initiate corrosion can be significantly shortened, reducing the effectiveness of the concrete cover in protecting the steel reinforcing. Estimates of the magnitude of this effect are presented.