Cracking behaviour in 3D concrete printed fibre-reinforced cementitious composites: A review

The integration of 3D concrete printing (3DCP) technology in cementitious composites offers significant opportunities, particularly in enhancing material efficiency and enabling greater design flexibility. However, the layer-by-layer deposition process introduces new challenges, especially regarding crack formation due to factors such as weak interfacial bonding and anisotropic mechanical behaviour. Fiber reinforcement has emerged as an effective strategy to mitigate crack development and enhance overall mechanical performance. This review examines the primary causes of crack initiation, key influencing factors, and mitigation strategies in 3DCP fibre-reinforced cementitious composites. Initially, it analyses crack formation in conventional cement-based materials, focusing on mechanisms of crack initiation, propagation triggers, and challenges associated with crack control. Traditional approaches such as steel reinforcement and chemical admixtures are also discussed. The review then explores recent advances in 3DCP techniques, including material selection, the role of anisotropy, and interlayer adhesion. Experimental findings suggest that maintaining a mini-slump flow diameter between 127 mm and 203 mm ensures suitable printability, while additives such as silica fume improve resistance to cracking. The nature of fracture propagation throughout the 3DCP process is specifically examined, emphasising how printing factors affect the evolution of cracks. An overview of the computational, experimental, and microstructural approaches for assessing crack behaviour is also included in the paper. Finally, the role of fibre characteristics, such as orientation, bridging mechanisms, and aspect ratio, is evaluated in relation to their effect on crack control in 3DCP composites. By synthesizing these findings, the study demonstrates pathways to enhance the durability and mechanical integrity of 3DCP fibre-reinforced cementitious composites, ultimately contributing to improved crack resistance and broader adoption of 3DCP in construction materials.