Incorporating coarse aggregates into 3D concrete printing from mixture design and process control to structural behaviours and practical applications: a review

Three-dimensional concrete printing (3DCP) is progressing from lab pilots to large-scale manufacturing, encountering limitations with conventional printable material - cement mortar. Coarse aggregate concrete (CAC) emerges as a promising alternative due to its superior material properties, cost-effectiveness, and sustainability, attracting considerable interest in academia and industry. This paper explores the integration of CAC into 3DCP, focusing on three critical aspects: mixture design of 3D printable concrete, innovative methods of 3D printing process, and structural behaviours of 3D printed concrete specimens, structural members and systems. It elucidates the relationships among mixture composition, processing parameters, early-age material properties, and printability requirements. Furthermore, particle-bed 3D printing technology for CAC is discussed, highlighting advantages and challenges compared to extrusion methods. Ultimately, this review provides valuable insights into the technical challenges and prospects of 3D printing coarse aggregate concrete (3DPCAC) technology, aiming to foster advancements in research and construction practices.