Performance of 3D-printed concrete columns with GFRP rebars under axial compression

3D concrete printing (3DCP) offers transformative potential in the construction industry by enabling rapid, cost-effective, and sustainable fabrication, yet its application to structural components is limited by concrete's brittleness and challenges in reinforcement integration. This study investigates the axial compression performance of 3D-printed concrete columns reinforced with glass fibre reinforced polymer (GFRP) bars. A hybrid construction approach was employed, in which 3D-printed concrete formed a permanent outer shell, while GFRP reinforcement cages were post-installed prior to casting the concrete core. Four columns, including conventionally cast counterparts of identical dimensions, were tested to assess load-displacement response, strain distribution, and failure mechanisms. The 3D-printed columns exhibited approximately 50% of the peak load of the mould-cast columns but demonstrated progressive, ductile failure, in contrast to the brittle failure observed in conventional specimens. These results suggest that 3D-printed columns could provide advantages in energy absorption, controlled failure, and modular construction, particularly where ductility is critical. The study further identifies interlayer bonding and reinforcement integration as key factors requiring optimization to enable reliable structural applications of 3DCP in the future.