Development of repairing methods for damaged structures due to chloride attack in the marine environment

Abstract

Many reinforced concrete structures around the world are deteriorated before their design life time due to environmental effects. Chloride attack is one of the major causes of deterioration of reinforced concrete structures. Chloride contamination can occur from the application of de-icing salts, from cast-in chlorides or from seawater as structures close to marine environment. In Sri Lanka there is no any type of repairing method to repair the damaged structures due to chloride attack. Most of the times the authorities replace the damaged bridges with new ones whenever there is a failure due to corrosion. This research is mainly focused on developing a repairing method to repair the corroded bridges in the coastal belt. There are many methods are used to repair the corroded structures, by this the most appropriate method is selected. There are several methods to repair damaged structure which is subjected to chloride attack. Electrochemical chloride extraction, applying a repair mortar and use of corrosion inhibitors are few of those methods. This research is mainly concerning about developing a repair mortar to repair the damaged reinforced concrete structures. A repair mortar is developed with less permeability characteristics with fly ash and silica fume. Calcium nitrate is used as an inhibitor additive to the repair mortar. Rapid chloride permeability test is carried out to few cylindrical samples to test the permeability of the repair mortar. Accelerated corrosion test is used to provide an aggressive environment to the test specimens. Finally the chloride concentration variation with the depth of the specimen was measured by titrating concrete powder samples with silver nitrate. Standard bridge rating systems are used to rate the bridges in coastal belt. Most suitable method to the country is selected.