Flexural performance of 3D-printed composite beams with ECC and recycled fine aggregate concrete: Experimental and numerical analysis

To overcome the difficulties of placing steel bars in 3D-printed concrete (3DPC), a novel reinforcement method combining engineered cementitious composites (ECC) and recycled fine aggregate concrete (RFAC) was proposed. Experiments on the flexural performance of 3D-printed composite beams with various ECC heights (15, 30, and 45 mm) and shear-span ratios (2.0, 2.5, and 3.0) were carried out. The test results indicated that the beams failed by bending, and the load-bearing capacities with ECC heights of 30 and 45 mm are roughly equivalent to those of the reinforced concrete beams with the longitudinal reinforcement ratios of 0.2%. Subsequently, a finite element model considering printed interfaces was established. The effects of interfacial bond strength, ECC height, and ECC strength on flexural performance were explored through a parametric study. The load-bearing capacity improvement by the increase of ECC height and strength may be limited by the bond strength of the printed interfaces.