The Impact of Coarse Aggregates on the Performance of 3D-Printed Concrete (2026-03)¶

Recent advancements in 3D-printed concrete (3DPC) have primarily focused on mortar-based mixtures, limiting understanding of how coarse aggregates (CA) influence printability and structural performance. While previous reviews have addressed general 3DPC rheology and mix design, systematic examination of CA-specific challenges and contradictions remains limited. This review addresses these gaps by analyzing 166 studies. Analysis reveals that 8–10 mm aggregates at 25–40% CA/A ratio provide optimal printability, with rheological windows of 150–5446 Pa yield stress and 2.15–295.4 Pa·s viscosity. However, significant contradictions exist across studies, stemming from variations in rheological and mechanical testing methods, deficiencies in aggregate characterization, and protocol inconsistencies. To address these challenges, the review introduces the “Printability Threshold Zone” framework, which establishes quantitative criteria for minimum fine content, optimal particle-size distribution, and maximum printable aggregate size. By evaluating the effects of CA shape, texture, and gradation on performance, this work provides systematic guidelines for developing sustainable, structurally efficient CA-based 3DPC.