This thesis investigates the potentials of hybrid 3D printed concrete formwork. Water-soluble polyvinyl alcohol (PVA) formwork allows for the creation of intricate forms that would be difficult, if not impossible, to create using standard formwork methods. Informed by finite element analysis, the PVA formwork allows for a gradient of variable porosities across a series of concrete units (blocks) in relation to structural loading and other possible design intentions. The goal is to optimize material use while addressing pathways for reusable formwork, reduced waste, and reduced embodied carbon. A series of blocks are fabricated for performance testing, and for a proof-of-concept quarter vault structure. The performance testing seeks to assess the blocks’ strength without reinforcement, and additional investigations explore the integration of macrofiber reinforcing to increase strength. The PVA formwork allows for designed anisotropy. When fibers are mixed into concrete, their orientations are typically random making them less effective. PVA formwork could allow for new hybrid formworks that allow for intentional placement of reinforcing fibers perpendicular to the compression force, potentially increasing their utility. The vault case study revealed that the porous vault structure uses 75 percent less material than a solid block structure with the same structural strength. It has been found that the PVA can be conserved through dehydration, which could allow the material to be reused in a cyclical system.