3D printed concrete reinforced with flexible fiber reinforced polymer strips or grids: Concept and bond tests

One of the major challenges for the wide application of three-dimensional (3D) printed concrete lies in the lack of a reliable and convenient reinforcement procedure for improving the durability and structural performance of the printed structures. This paper presents two innovative reinforcing methods using fiber reinforced polymer (FRP) grids or strips, i.e., the synchronous printing method and the inter-layer laying method. By capitalizing the flexibility of FRP grids/strips, the proposed reinforcing methods aim to achieve the printing of concrete and reinforcement synchronously. As the first step, an experimental program was conducted to evaluate the bond performance between FRP and 3D-printed concrete. To this end, 3D-printed concrete specimens with FRP strips or grids embedded were fabricated and pull-out tests were conducted. The effects of various key parameters on the bond performance were examined in detail. The test results showed that the bond strength between FRP and 3D-printed concrete could reach above 14.0 MPa for specimens fabricated with the synchronous printing method and above 4.0 MPa for those with the inter-layer laying method, demonstrating the great potential of the proposed reinforcing methods in practice.