In-Process Embedded FRP Grid for Enhanced Flexural Performance of 3D Printed Concrete Plates (2026-02)¶

Functionally graded concrete (FGC) is increasingly used in structural engineering for its customizable properties, and 3D-printed concrete (3DPC) provides an effective method for its fabrication. However, the layerby-layer deposition nature of 3DPC complicates steel reinforcement placement, often leading to poor flexural performance, while its higher porosity can accelerate steel corrosion and reduce durability. To address these issues, a dual-nozzle system was developed that is capable of the in-process embedment of corrosion-resistant fiber-reinforced polymer (FRP) grids during the fabrication of FGC using 3DPC technology. The proposed method was evaluated using threepoint bending tests, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) to examine how FRP grid properties and printing parameters affect flexural performance. The results demonstrate that the embedded FRP grids significantly enhanced the flexural performance: flexural strength, energy absorption capacity, and ductility increased by up to 110.2%, 1744.3%, and 479.2%, respectively. Flexural performance improved with higher FRP grid content and extrusion rate, whereas it declined with increasing nozzle travelling speed, interval time, and nozzle standoff distance. MIP tests indicated that adding FRP grids raises interlayer interface porosity, especially pores larger than 5000  nm. SEM further confirmed that pore morphology at the FRP gridconcrete interface critically influences flexural performance. The findings highlight that in-process embedded FRP grid reinforcement offers a practical pathway to automated, durable, and high-performance 3D-printed cementitious composites.