Structural behaviour of 3D-printed concrete segmental beams with polymer concrete joints under post-tensioning

Three-dimensional concrete printing (3DCP) provides a formwork-free and rapid alternative to traditional concrete casting techniques. However, its application in large-scale structures is constrained by printer size, necessitating segmental construction. The structural performance of such systems is governed by interfacial behaviour influenced by surface irregularities and anisotropy inherent to 3D printing. This study evaluates the structural behaviour of 3D-printed segmental beams using polyvinyl ester polymer concrete (PVE-PC) as a joint material. Three large-scale beams, each composed of seven modules, were tested under four-point bending with varying levels of post-tensioning. The results show that PVE-PC provides effective load transfer between modules when sufficient compressive confinement is present, without compromising overall stiffness. While initial stiffness remained similar with and without post-tensioning, post-tensioning increased the cracking load. However, increasing the compression-side post-tensioning beyond a certain limit did not further increase the cracking load; instead, it altered the crack location and shifted failure from interface-controlled behaviour to ductile flexural response within the 3D-printed module. Post-tensioning also restored and enhanced the performance of previously damaged specimens, indicating its potential as a retrofit strategy. Overall, polymer concrete combined with post-tensioning provides a viable approach for achieving structural continuity and reliable performance in 3D-printed segmental beams.