Behavior of existing RC columns repaired with FRCC

Recent earthquakes confirmed the high vulnerability of existing reinforced concrete (RC) structures even to moderate seismic events. The use of Fiber Reinforced Cementitious Composites (FRCC) jacketing is an innovative technique for repairing and strengthening low damaged existing RC members. However, little research has been developed in this field and experimental works that attest the reliability of such a system are poor. In this work, a RC column typical of existing structures was pre-damaged under quasi-static cyclic horizontal loading and then repaired with FRCC jacketing and re-tested. In particular, the repair technique consists in replacing the existing concrete cover with a thin layer (i.e. 30mm) of FRCC for the entire length of the column. The FRCCs selected in this work are a class of fiber cement composites with fine aggregates that exhibit a strain-softening behavior in tension after first cracking (i.e. quasi-brittle behavior) and high strength in compression. The behavior of repaired column has been compared with the one of a control specimen, which experienced a quasi-brittle failure governed by the flexure-shear interaction. Failure modes and force-drift relations are presented and discussed, along with a detailed strain and curvature analysis supported by the Digital Imagine Correlation (DIC) outcome