Effect of Dissimilar Cover to Reinforcement on Different Faces of Reinforced Concrete Section

For achieving the desired strength, serviceability and durability of the individual members, as well as for the overall performance of the reinforced concrete structures, clear cover to reinforcement is very important. Depending on the type of member, exposure conditions, fire rating, and other factors, various codes stipulate the values of clear cover for respective countries. Being sheltered from the direct action of sun and rain, the internal exposure conditions can be less harsh compared to the external one. This paper examines the implications of providing dissimilar cover on different faces of concrete members based on the aforementioned premise. It is concluded from the results of two typical case studies that, if internal chloride concentration is higher than 50–60% of the external ones, corrosion cracks would appear on the internal faces earlier to the external ones. This will prevent the early warning, and timely intervention for maintaining the structural health. Furthermore, the provision of dissimilar clear cover on various faces of the same member would render the detailing and execution of such job laborious, time-consuming, as well as prone to mistakes. The authors suggest providing same clear cover on all faces of concrete members, decided based on the worst exposure conditions encountered by the structure—as a conservative but straightforward solution to this debate.