STATE OF THE ART IN REPAIR AND STRENGTHENING METHODS OF DETERIORATED CONCRETE BRIDGE STRUCTURES

This paper summarizes the current development for repairing and strengthening deteriorated concrete bridge structures in Japan, especially those deteriorated due to alkali-silica reaction (ASR) and chloride attack. Generally, surface treatments are applied as the repair method due to ASR and chloride attack. Barrier coating and penetrating sealer are two methods that are actively applied as surface treatments in Japan. An investigation of repaired concrete bridge structures using these methods indicate that acrylic-based surface coatings are the most suitable method for repairing concrete structures, and the silicon-based compounds repair concrete structures with low risk of corrosion. Furthermore, the use of sodium or potassium for silicate-based surface treatments should be avoided, as these solutions may exacerbate ASR. This finding was backed up by an accelerated mortar bar test experiment under a modified ASTM C1260 test method. The results show that large ASR expansion occurred on mortar bars immersed in sodium silicate solution (Na2SiO3). In regards to strengthening, CFRP sheet bonding, concrete jacketing and PC-confined method with prestressing steel wire were applied for concrete bridge structures. Especially for the PC-confined method, this method can be applied not only as an earthquake strengthener but also an ASR expansion controller on deteriorated bridge piers.