Flexural properties of reinforced concrete slabs using highly ductile concrete (HDC) permanent formwork system

To optimize the construction process, this study proposes a highly ductile concrete (HDC) permanent formwork system, which consists of a steel truss and an HDC shee. It fully utilizes the advantages of the mechanical properties of HDC and factory prefabrication. The study first investigates the mechanical properties of a prefabricated HDC permanent formwork system under construction loads. The results show that the specimens maintain an elastic response with on-site support at a distance of 3.2 m, satisfying the requirements of the construction stage more comprehensively. Subsequently, a reference reinforced concrete (RC) slab and two identical composite slabs using the HDC permanent formwork system are tested as simply supported slabs under four-point bending. The results indicate that the bridging effect of polyethylene (PE) fibers allows the crack widths of the composite slabs to be controlled. Multi-crack behavior is observed in the HDC sheet. In addition, the HDC sheet improves the flexural behavior of the RC slabs in terms of flexural capacity, stiffness, and energy absorption owning to the strain-hardening behavior of the HDC composites. Finally, a calculation method based on the plane-section assumption is used to predict the flexural capacity, stiffness, and corresponding deflection of the composite RC slabs.