Bond Behavior of Epoxy Coated Rebars at The Beam Column Joints for Application in Corrosive Environment

Abstract

The corrosion of steel reinforcing bars in concrete can reduce its durability in coastal areas. Using the right concrete additives and rebar coating can slow the corrosion of steel in reinforced concrete structures. Epoxy-coated rebar (ECR) can be used to resist corrosion, but it shows low bond behavior. Moreover, the behavior of epoxy coated rebars in resisting earthquake forces and energy dissipation is still not well understood due to weakened bond with adjoining concrete. This research focuses on studying ECR to assess the bond behavior of rebars with concrete with different mixes. 42 x pullout samples are cast having 10mm,13mm, 19mm and 25mm diameter. Each diameter of rebar is divided into three groups: standard black rebar, standard coated rebar, and headed coated rebar. To check the bond behavior of the rebar based on the particle distribution of the fine aggregate, two different types of fine aggregate are studied: finer aggregate with fineness modulus of 2.17 and coarser aggregate with fineness modulus 2.65. The results showed that the bond stress of coarser aggregate performed better as compared to finer aggregate. The headed rebars performed better, and an increase in bond behavior was recorded as compared to standard coated rebar, which failed either through splitting failure or debonding of the head. As the diameter of rebar increases, a decrease in stiffness and bond stress was recorded in both batches. Two types of failure were recorded: pullout failure and splitting failure. To find out the structural performance of the coated rebars, three full-scale beam column joints (BCJ) were experimentally tested: standard black rebar reinforced BCJ, standard coated rebar reinforced BCJ, and headed coated rebar reinforced BCJ. The exterior beam column joint was selected for testing as it is the most critical joint in the frame structure. The beam rebars yielded have been observed after 16 cycles. Epoxy-coated rebars performed well in BCJ, both standard and headed BCJ. Overall, standard coated rebars from BCJ performed well. The control sample showed initial high stiffness until 0.5% drift ratio; after this point, drastic changes have been observed. A large difference in stiffness has been recorded in control push-pull stiffness; the pull direction of control BCJ was degraded slowly. Standard-coated and headed-coated samples degraded gradually. Standard-coated rebar shows high ductility and higher cumulative energy dissipation.