Performance of RC Columns Strengthened with Fabric-Reinforced Cementitious Matrix (FRCM)

Abstract

A recently emerging technique to strengthen existing concrete structures using Fiber-Reinforced Cementitious Matrix (FRCM) is introduced to retrofit structural members. FRCM is an inorganic matrix that consists of textile layers sandwiched between cementitious mortar layers. The main objective of this study is to investigate the response of reinforced concrete (RC) short columns strengthened with poly-paraphenylene-ben-zobisoxazole (PBO) FRCM under pure axial compression. The aim is to study the effect of the column cross-section shape as well as the number of FRCM layers on the effectiveness of PBO-FRCM systems in improving the strength and ductility of pre-damaged and non-damaged RC columns. A total of 10 columns with a clear height of 800 mm and a longitudinal reinforcement ratio of 1.5% were cast and tested monotonically until failure. Also, columns were either unwrapped which served as controls, wrapped with 2 PBO-FRCM layers or wrapped with 4 PBO-FRCM layers. Experimental results showed that strengthening pre-damaged RC columns with PBO-FRCM is highly efficient in restoring and increasing the original capacity, where the capacity increased with the increase of number of PBO-FRCM layers. Circular columns showed a better improvement in ultimate capacity where the capacity increase ranged from 38 to 71%. Also, strengthening short RC columns with PBO-FRCM increased the column ductility with a range of 19 to 82%. Finally, theoretical ultimate capacities of strengthened columns calculated using the provisions of ACI 549.4R-13 code showed that the code is accurate at estimating the capacity of short RC columns strengthened with PBO-FRCM.