Strengthening pre-damaged RC square columns with fabric-reinforced cementitious matrix (FRCM): Experimental investigation

This study investigates the effectiveness of using fabric-reinforced cementitious matrix (FRCM) systems in repairing pre-damaged reinforced concrete (RC) square columns. Two groups of columns were fabricated and tested under concentric loading up to failure. Columns of each group had different spacing between their transverse reinforcement to investigate the effectiveness of FRCM reinforcement in confining the columns. The columns were subjected to two pre-damaging criteria prior to strengthening. Four columns were loaded up to their yielding capacity and then unloaded while the other two columns were subjected to three cycles of fatigue loading that ranged between 2% and 75% of the unstrengthened column's capacity. The pre-damaged columns were then strengthened with either two or four layers of polyparaphenylene-benzobisoxazole (PBO)–FRCM system. Test results showed that confining the pre-damaged columns with PBO–FRCM systems resulted in 7–42% enhancement in their load–carrying capacity and 47–272% improvement in their ductility. The predicted columns’ capacity calculated as per ACI 549 guidelines showed a good agreement with the experimental results. The experimental–to–predicted capacity ratio ranged between 0.82 and 1.03 for columns with tie spacing of 180 mm and between 0.92 and 1.09 for columns with tie spacing of 90 mm.