Experimental behavior of reinforced concrete columns confined with carbon-FRCM composites

Confinement of concrete elements by means of fiber reinforced polymer (FRP) or fiber reinforced cementitious matrix (FRCM) has been largely investigated in literature, however such studies dealt mainly with small scale specimens rather than with fully reinforced concrete (RC) ones. Here, the results of an experimental campaign where twelve RC columns were tested under axial compressive loading are shown. Among the test specimens, eight were confined with carbon-FRCM (CFRCM) and four were used as control. The following variables were considered as influencing parameters: section geometry, i.e. columns with circular or square cross-sections; amount of transverse steel reinforcement, i.e. two stirrups spacings; and lastly the number of fiber layers, namely one or two layers. Stress vs. axial strain curves and fiber hoop strains were analyzed to derive the strength gain and specimens’ ductility. Additionally, strains of transverse steel reinforcement were monitored, to assess how the internal reinforcement interacts with the confinement performance of the external CFRCM jacket. Results obtained here represent better the in-situ condition of axially-loaded members, that include inner longitudinal and transverse reinforcement.