Elastic wave based evaluation of CFRP protected RC structures subjected to corrosion

摘要

Determination of the state of hidden corrosion propagation inside concrete continues to be a major challenge for the evolving structural health monitoring industry. Numerous techniques such as Elastic wave based methods, vibration-based methods, Electrochemical techniques, etc., have been deployed for corrosion detection. Once the corrosion progression is detected, a suitable retrofitting or corrosion impeding technique is of equal importance. In this paper, reinforced concrete (RC) cylinders subjected to corrosion induced damage are protected passively and actively. Passive protection implied wrapping of reinforced concrete with carbon fiber reinforced polymer (CFRP) sheets whereas active protection implied providing cathodic protection in conjunction with application of wraps. RC cylinders corroded to 4 different levels of damage were protected after 4, 8, 12, and 20 days of exposure to accelerated corrosion. The corroding samples were monitored using an elastic wave-based non-destructive testing technique known as the Ultrasonic Guided wave technique. Two modes i.e. Surface seeking mode L (0, 1) at 0.1 MHz and L (0, 7) at 1 MHz were used. The variations in surface seeking mode and core seeking mode signal amplitudes indicated that corrosion impediment offered by active protection was superior. From the mass-loss measurements, the samples protected actively after 4, 8, 12, and 20 days underwent 2.11%, 2.3%, 4.25%, and 7.25% of mass-loss respectively, whereas the passively protected samples exhibited 3.1%, 3.4%, 5.1%, and 8.3% mass-loss for the same time intervals. Along with corrosion impediment, the actively protected samples exhibited higher pull-out strength (9.8 MPa, 9.6 MPa, 8.9 MPa, and 8.3 MPa) than passively protected samples (10.1 MPa, 9.2 MPa, 7.8 MPa, and 7.3 MPa) for protection initiation after 4, 8, 12 and 20 days of accelerated corrosion.(c) 2021 Elsevier Ltd. All rights reserved.