Experimental investigation of the performance of concrete columns strengthened with fiber reinforced concrete jacket

This paper presents an experimental study on the axial compressive behavior of concrete columns retrofitted and confined by fiber-reinforced concrete (FRC) jackets. Three different engineered cementitious composite (ECC) mixes containing high-strength polyethylene fibers at three fiber volume fractions of 0%, 1%, and 2%, and one ultra-high performance cementitious composite (UHP) mix at fiber volume fraction of 4%, were prepared to produce FRC jackets around the core concrete. Horizontal stirrups were used in the FRC jackets with three different horizontal reinforcement ratios to investigate the effect of the level of confinement and the interaction between the conventional reinforcement and fibers. The results show that specimens having no fiber or stirrup in their retrofitting jacket exhibit a brittle behavior and only those containing both stirrup and fiber provide a ductile behavior. It was also observed that the lateral strain of the jacket layer at a given axial strain increased with an increase in the fiber content, indicating an increased rate of dilation for the jacket concrete at a higher fiber volume fraction. It was also found that the best solution to enhance both ductility and strength of columns using FRC jacket is to include a minimum of both fiber content and reinforcement in the jacketing layer. The observations of this study reveal the great potential of the use of FRC jackets in retrofitting of structural members, especially columns in seismic regions.