A compendious review on lack-of-fusion in digital concrete fabrication

Abstract

Abstract Lack-of-fusion (LOF) in digital concrete fabrication is one of the paramount technical issues that must be elucidated before mass industry implementation of this emerging technology. This review paper initially accentuates the ramifications of poor interlayer bonding, which include impaired mechanical and thermo-mechanical performance in the hardened concrete state, durability issues pertaining to corrosion of reinforcing steel and the complexities associated with numerical modeling of 3D printed structures. Focus is then placed on the mechanisms that induce LOF, which constitute an intricate combination of mechanical interaction, chemical bonding and intermolecular forces between filaments. Comprehension of these mechanisms is required to develop appropriate solutions to this problem. The paper presents current interlayer bond strength (IBS) characterization tests and their associated (dis)advantages. Lastly, solutions employed in literature to reduce LOF are presented to give readers a holistic perspective of the current state-of-the-art surrounding LOF in 3D concrete printing.