Monitoring of actively protected frp wrapped rc structures from corrosion using guided waves

Abstract

One of the major causes of catastrophic failures in reinforced concrete structures such as bridges, dams and buildings is the deterioration of reinforcing bars due to corrosion. If the degradation remains unnoticed inside concrete, it further accelerates and causes huge loss of life and property. Removal of concrete to visually inspect the reinforcement is detrimental to the structure. Hence, it is imperative to develop a non-intrusive health monitoring technique for early detection of corrosion related damages in steel embedded in concrete. The primary object of this work is to evaluate the effectiveness of Active protection provided to RC structures from corrosion using Ultrasonic Guided Waves. Corrosion will be accelerated using impressed current method and CFRP shall be used for Active protection. Guided ultrasonic waves offer a potentially attractive solution. In the present study, bars embedded in concrete are subjected to corrosion and also protected using Active Protection. Carbon Fiber Reinforced Polymer has been used for Active protection of RC structures from corrosion. These materials have received great attention and their applications to structural repair and retrofit have grown significantly in recent years. CFRP fabric is largely employed because it offers superior performance such as resistance to corrosion, high stiffness- to weight ratio, high tensile strength, light weight, high durability and easy installation etc. These protected specimens are monitored ultrasonically using longitudinal guided waves. A mode with minimal attenuation and mode shape that is suitable for detection of a particular type of damage is chosen from dispersion curves. For this purpose, we conduct the Pulse Transmission Investigations. The reinforcements have been excited at one end only with an ultrasonic pulse using piezoelectric transducer which acts as the transmitter and the receiver itself. Ultrasonic testing is carried out on bars in concrete by simulating corrosion in the form of area loss and delamination. It is observed that corrosion of reinforcing bars in concrete is discernible using ultrasonic guided waves.