Accelerated Corrosion and Repair of Reinforced Concrete Beams Using FRP Wraps

Abstract

Corrosion of reinforcing steel and subsequent concrete deterioration is a major prob- lem faced by the construction industry. Researchers have attempted for improvement in different properties of structural members by using various types of innovative materials and techniques. Fiber reinforcement polymer(FRP) is composite material, which withstands higher tensile strength as well as having other advantages like non- corroded, and lightweight. FRP wrapping is one of the most innovative solutions for repair and strengthening of partially or fully damaged structures as compared to that of conventional repair methods. Hence, an attempt is made hereby to evaluate com- parative performance of reinforcement concrete (RC) beams using various wrapping materials under the corrosion effect. Total 37 RC beam specimens are cast 21 beams are of cross sectional dimensions 150mm x200mm with an effective span of 750 mm. 16 beams are having cross sectional dimensions of 150mm x250mm and effective span of 1200 mm. All beams are cast using M25 grade of concrete Variations employed in present study are different techniques of accelerated corro- sion, different FRP materials for repair and chronological order of conducting repair operations for RC beams. 21 beams are immersed in two different acids like HCl and H2SO4, respectively. 16 beams are corroded by using impress anodic current. All beams subjected to 8 wetting-drying cycles each of 2 weeks. During wet cycle the beams are immersed in water, up to tension reinforcement and in dry cycle, the beam is kept in open atmosphere for drying. Protection of some beams is conducted after 28 days of curing. Beams are wrapped before corrosion with use of GFRP and CFRP sheet. The beams are damaged due to corrosion. Corrosion rate is assessed throughout 8 cycles using the half-cell potentiometer Similarly, quality of concrete is assessed throughout 8 cycles using UPV. After completion of 8 cycles damaged beams are repaired with GFRP and CFRP sheet. After completion of wrapping beams are subjected to air curing. Testing of beams is conducted using two point load. Com- parative failure loads and defection is observed for all wrapped and unwrapped RC beams. The application of a anodic current through a sample submerged in sodium chloride water is very effective. More cracks are observed for beams immersed in HCl compared to H2SO4. Higher corrosion rate is observed for unwrapped beams as compared to that of wrapped beams after completion of 8 cycles. UPV readings show that quality of concrete observed is quite good after comple- tion of 8 cycles for all beam specimens. In Damaged beams load carrying capacity decreases due to their immersion in HCl and H2SO4. Reduction in load carrying capacity is observed for GFRP and CFRP wrapped beams before and after HCl and H2SO4 immersion respectively. Least defection has been observed in beam wrapped by GFRP and CFRP as compared to unwrapped control beam. The corroded beams has higher defection than the control beams due to degrading stiffness of the beams. Lower strain has been observed to GFRP and CFRP wrapped beams compared to unwrapped beam. Higher strain and defection observed for GFRP wrapped beams compare to CFRP wrapped beams immersed in HCl and H2SO4. Due to impress anodic current technique, reduction in load carrying capacity is observed for beams. Load carrying capacity reduce due to corrosion of steel in concrete through GFRP wrapping is applied on beam after initiation of corrosion. The GFRP wrapped after corrosion has lesser defection compared to control beam. The CFRP and GFRP wrapped after corrosion has least defection compared to control beams. lesser reduction in load carrying capacity is observed for beams wrapped by CFRP compared to GFRP after impress anodic current. It can be observed from above discussion that CFRP and GFRP wrapping has proved excellent material in protection of concrete against deterioration due to acids as well as under corrosive environment.