Interfacial bond properties between 3D printed engineered cementitious composite (ECC) and post-cast concrete

Buildings can be rapidly constructed using 3D printed concrete technology without formwork, garnering increasing attention within the construction industry. The effects of different printing parameters on the splitting tensile strength, shear strength, pore structure, and micromorphology of the interface between 3D printed ECC and post-cast concrete were investigated, including single-layer printing height, fiber content, and recycled sand replacement ratio. The results indicated that as the fiber content and single-layer printing height increased, the interfacial bond strength was initially enhanced while subsequently decreased, with optimal bond strength achieved at a 15 mm single-layer printing height. Moderate fiber content and single-layer printing height were beneficial for interfacial bond strength. Meanwhile, the interfacial bond strength was reduced due to the evolution of interfacial pore structure after the incorporation of recycled sand. The splitting tensile strength and shear strength of the interface between 3D printed ECC and post-cast concrete decreased by 36.1% and 35.8%, respectively, when the replacement ratio of recycled sand in ECC was 100%. Additionally, models for the interfacial shear strength between 3D printed ECC and post-cast concrete were proposed.