Bonding properties between 3D printed coarse aggregate concrete and rebar based on interface structural characteristics

The bonding properties between 3D printed concrete and rebar are a critical factor in determining the performance and service life of 3D printed concrete building structures. Due to the difficult elimination of pores formed at the interface between the rebar and concrete during rebar placement, it becomes a key factor affecting the interfacial bonding performance. This work focuses on the structural defect characteristics of the bonding interface between 3D printed natural coarse aggregate concrete (3DPNAC) and ribbed rebar, the bonding properties of 3DPNAC-rebar with different rebar arrangement directions (parallel, vertical, 45 degrees) were investigated through artificial placement of the rebar and compared with those of 3D printed mortar (3DPM) and cast concrete. The results showed that the bonding strength between 3DPNAC and rebar was higher than that of 3DPM, and the distribution characteristics of pore defects and natural coarse aggregate were the primary causes of the structural differences between the bonding interfaces of 3DPNAC and 3DPM with rebar. The partition distribution and geometric configuration of pore defects in the bonding interface area were identified as pivotal factors in the degradation of the bond strength between 3DPNAC and rebar. Based on the structural composition of the 3DPNAC-rebar bond interface, a bond interface-partitioning model was proposed to elucidate the bond-slip damage mechanism. Finally, a bond-slip model of 3DPNAC and rebar was established. This study can provide important guidance for the structural design and application of 3D printed concrete structures with rebar.