ABSTRACT
Robert-Bourassa/Charest (RBC) overpass was a highway bridge structure (Quebec, Canada) that was built using an alkali-silica reactive limestone aggregate. Over nearly 5 decades, many signs of distress developed on the various structural members of the structure mainly due to alkali-silica reaction (ASR), freeze-thaw (FT) cycles, as well as steel corrosion. One of the major concerns regarding RBC structural long-term performance was related to the distress degree of the Y-shaped columns and thus a 1067number of rehabilitation techniques including surface treatments (rigid coatings, silane/siloxane based products) and structural confinement (GFRP wrapping systems) were adopted to suppress further ASR-induced expansion and damage. In 2010/2011, prior to its demolition, several cores were extracted from the different members of RBC, which enabled the microscopic and mechanical characterization of damage from the various treated columns. This paper presents a comparison of the efficiency among the different rehabilitation techniques used to mitigate ASR in RBC columns. Results show that different damage degrees are found according to the group of columns; greater SDI and PDI and lower modulus of elasticity values were obtained from the North-West specimens, followed by the South-West/East cores. Microscopic analyses showed evidence of ASR and freeze and thaw mechanisms and marginal to moderate expansion & damage levels were obtained from the distinct columns assessed.
