Title : CATHODIC PROTECTION OF CONCRETE STRUCTURES
Authors : P. SRINIVASAN
Publication :
Volume :
Pages : 87-108
Price : 250
Abstract : One of the major problems of durability of reinforced concrete structures is the corrosion of reinforcement and its consequent damage leading to early failure of reinforced concrete structures. Steel reinforcement in concrete remains protected against corrosion as long as it is passive. The two processes responsible for depassivation and subsequent corrosion of steel rebars are the carbonation leading to reduction in pH and ingress of chloride ions into the cover concrete. After depassivation, the reinforcement corrodes and the rate of corrosion depends of the type of rebars used in concrete. Different types of corrosion protection/prevention are available, the most commonly used in India are the coating to rebars, concrete surface coatings and corrosion inhibitors. These methods have limitations depending on the chloride content in concrete. Cathodic Protection (CP) is the only method that can be used to rehabilitate reinforced concrete structure irrespective of the chloride content in concrete. ACI, AASHTO and Federal Highway Administration, USA, have declared that Cathodic Protection (CP) is the most effective way of preventing corrosion of steel in concrete. The Cathodic Protection are of two types namely impressed current and galvanic. The impressed current system is widely used and consists of a rectifier, anode, wiring and reference electrode. Various types of anodes are used such as metal wire mesh made of different elements and conductive coatings applied on the concrete surface. Different types of reference electrodes are used for monitoring. The difficulty of applying the CP in concrete structures is the high resistance offered by concrete. The bond strength of the reinforcement may get reduced depending upon the intensity of the current applied for cathodic protection. CP systems are to be monitored regularly. This paper highlights the theory and application of the cathodic protection in reinforced concrete structures.