ABSTRACT
Since deicing salt is sprayed on the reinforced concrete (RC) road bridge decks in the cold regions in winter season, complex deterioration of salt damage, freezing damage under a salt environment and alkali silica reaction (ASR) is often found on bridge decks in recent years, even in areas with low traffic. Therefore, it has been pointed out that it is necessary to enhance the durability of the RC road bridge decks by introducing new concept in durability design. In this study, the performance of casted concrete was evaluated at the stage of the construction process in order to ensure the durability of casted RC road bridge deck. Multiple defense concept was introduced by applying anti-rust coating rebar and high durability concrete against salt damage, freezing damage and ASR. The use of fly ash is a core countermeasure for high durability concrete, because fly ash is effective against both ASR and chloride attack. The long term wet-curing is required to obtain anti-chloride ingress performance. Also, air content was designed at 6% to obtain anti-frost performance. This value is higher than the conventional target value (4.5%). This is because pumping and vibrating processes reduce the air content during concrete casting. Finally, an expansive agent was also used to reduce the risk of shrinkage cracks by introducing chemical prestressing. The construction plan was made carefully referring to the laboratory tests and trial construction with site mock up. Then, actual RC road bridge deck was constructed. It was confirmed that the RC road bridge deck achieved the performance expected in the durability design by various non-destructive tests and investigations at construction site. Consequently, the effectiveness of the proposed performance evaluation procedure at the stage of the construction process for RC bridge deck is demonstrated.
