Performance Evaluation of Corroded Reinforced Concrete Columns Strengthened with FRCM under Cyclic Loading and Subsequent Corrosion Rate

This study investigates the performance of corroded reinforced concrete (RC) columns strengthened with Fabric Reinforced Cementitious Matrix (FRCM) composites. Seven column–foundation specimens were tested under cyclic lateral loading to evaluate their behavior. The main experimental variables included the corrosion process (before and after strengthening) and the adopted strengthening method. Some of the corroded specimens were re-exposed to a corrosive environment after strengthening to estimate the process of subsequent corrosion. The strengthening was carried out using a carbon-based FRCM (C-FRCM) system, both independently and in combination with embedded Glass Fiber Reinforced Polymer (GFRP) bars (hybrid method). The experimental results were compared with the design provisions of ACI 549.4Rf code. The aims of this study are as follows, evaluate the performance and load carrying capacity of corroded columns, identify their failure mechanisms, assess ductility factor, energy dissipation capacity and examine the influence of strengthening on the rate of re-corrosion process. The results revealed that corrosion significantly reduced the load carrying capacity of the columns. Corrosion was found to be non-uniform along both longitudinal and transverse reinforcement bars. It led to brittle failure and a considerable decrease in energy absorption. Moreover, the FRCM and GFRP strengthening system exhibited a notable improvement in structural performance, particularly in the corroded specimens. Comparison between experimental results and ACI 549.4R code predictions indicated that the code provisions are conservative. Furthermore, the proposed strengthening method reduced the corrosion rate by approximately 16%.