Interfacial constitutive model of 3D printed fiber reinforced concrete composites and its experimental validation

Abstract

In recent years, 3D printing has been rapidly promoted and applied in the field of civil engineering and construction, and has been developed from landscape maintenance structures to load-bearing structures. Different from cast-in-place concrete materials, the contact interfaces between adjacent layers or filaments formed under the additive stacking process lead to distinct mechanical anisotropy of 3D printed concrete materials, and thus the mechanical model of traditional concrete materials and the design method of reinforced concrete structures are inapplicable to 3D printed concrete materials and structures. The establishment of 3D printed concrete materials is therefore of great significance to the design of 3D printed concrete structures. Currently, there is still a lack of research on the constitutive models of 3D printed fiber reinforced concrete. This study tested and analyzed the tensile and shear performances of 3D printed concrete reinforced with steel fibers and polypropylene fibers. According to the distribution porosity, the interface thickness of 3D printed fiber reinforced concrete was measured and determined. The constitutive modeling of mechanical anisotropy of 3D printed fiber-reinforced concrete were established based on the theory of damage fracture of concrete and experimental results. Results show that the interfacial tensile strength at layers and filaments of 3D printed concrete with steel fiber were 6.2 MPa and 6.9 MPa, while the capacities of 3D printed concrete with polypropylene fiber were 4.5 MPa and 4.7 MPa, respectively. The fracture damage constitutive model adopted in this study has favorable fitting degrees, which would contribute to the further finite element simulation and structural design of 3D printed concrete.