Evaluating mitigation methods for chloride induced corrosion of reinforced concrete structures

Abstract

Corrosion of steel reinforcement in concrete causes the deterioration of concrete structures. As a result, the corrosion loss consumes considerable portion of the budget of a country by ways of either restoration measures or reconstruction. Once the corrosion signs appear, it may be too late to prevent further deterioration and no proper method to re-passivate the corroded reinforcement steel. Properly monitoring the structures for corrosion performance and taking suitable measures at the appropriate time could contribute enormous saving. Objective of this study is to evaluate the repairing methods for Reinforced Concrete (RC) structures, which were corroded due to chloride attack. Laboratory experiments were conducted with RC beams. The beams were cast by using Grade 20 concrete and steel bars of 16 mm diameter. Cathodic protection and electrochemical chloride ion extraction were used as treatment methods. For both methods, current was supplied by using DC power supply. The positive and negative terminals were connected to the copper mesh laid on concrete surface and steel reinforcement bars of beams, respectively. For electrochemical method, calcium hydroxide was used as an electrolyte media. Cathodic protection and electrochemical chloride ion extraction treatment remove 49.33% and 68.53% of total chloride ions from the embedded steel reinforcement bar area, respectively. Catholic protection method prevented the further corrosion possibly by removing the chloride ions, producing alkaline condition, which helps to form iron oxide film surrounding the steel bars. With the electrochemical chloride ion extraction method, calcium hydroxide helps to increase the efficiency of cathodic protection by removing the chloride ions, which approached to the copper mesh, and by reducing the time duration of cathodic protection.