Behavior of artificially corroded RC beams strengthened with CFRP and hybrid CFRP-GFRP laminates

Abstract

Steel corrosion is a major degradation factor for the reinforced concrete (RC) infrastructure and necessitates a costly repair after short service life. Predicting the strength of corroded and retrofitted structural elements while under service is a challenging task. For this purpose, the impressed current technique is frequently used to achieve the desired degree of corrosion in RC members in the laboratories. This study investigates the effectiveness of this technique on laboratory-scale RC beams and evaluates the behavior of severely corroded beams rehabilitated with carbon fiber-reinforced polymers (CFRP) and the hybrid of CFRP and glass-FRP (GFRP) laminates. Extensive literature is available on the behavior of sound RC members strengthened with FRPs, however, data are scarce on the behavior of corroded-strengthened RC beams. The RC beams were deteriorated by applying an impressed current of 750 µA/cm2 for 15 days. All the beams were tested under four-point bending till failure. The reinforcement mesh was non-uniformly corroded; the flexural bar facing the external cathode experienced a higher degree of corrosion than the opposite bar and the actual applied impressed current reached as high as 2388 µA/cm2. The flexural strength of the degraded beams, with 37 % weight loss on the main rebars, was 41 % less than counter-part sound beams. On the other hand, the CFRP strengthening regained the strength of degraded beams by 45 % compared to the unstrengthened-degraded beams. Whereas the CFRP-GFRP hybrid laminates regained strength up to 60 % compared to the counterpart-degraded beams and 12 % higher than the sound beams. This study demonstrated that a desired degree of corrosion could be achieved on a particular reinforcement portion with the impressed current technique. In addition, CFRP and CFRP-GFRP laminates are effective external strengthening techniques for rehabilitating degraded concrete infrastructure.