Testing and modeling reinforced 3D concrete printing

3D Concrete Printing (3DCP) provides several advantages, including construction productivity and sustainability, although the presence of cold joints reduces structural performance, particularly in zones subjected to tensile stresses. In addition, it is difficult to reinforce 3DCP structures with conventional steel rebars, generally used to reinforce concrete. To solve these problems, reinforcements are automatically inserted by means of a new system, in which pin-shaped reinforcement connects the concrete layers of traditional 3D printing (herein called R3DCP). To analyze the behavior of R3DCP beams, an experimental campaign has been performed and described in this paper. It includes material characterization, pullout tests to quantify the bond–slip between pin reinforcement and printed material, and full-scale four-point bending tests on 3DCP and R3DCP beams. Moreover, a new three-stage modeling approach, in which the contribution of discrete pin reinforcements is explicitly incorporated through a bond–slip equivalent constitutive relationship, is proposed. The good agreement between experimental findings and numerical results corroborates the effectiveness of the proposed reinforcing system, supporting future design guidelines for R3DCP