Influence of Slag/Fly Ash as Partial Cement Replacement on Printability and Mechanical Properties of 3D-Printed Concrete

Three-dimensional printing is an emerging technique that has received significant attention in the construction industry. This study presents an investigation into the printing and hardened properties of 3D-printed concrete (3DPC). Both fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used to replace cement in different ratios (0%, 25%, and 50%) to produce 3DPC. Extrudability and buildability tests were performed to evaluate the effects of FA and GGBFS in various proportions on the printing properties of 3DPC. Additionally, the hardened properties of 3DPC were determined. Test results show that all mix designs meet the printing requirements of 3DPC. The specimens with a higher proportion of GGBFS exhibited higher unit weight and compressive and flexural strength, but lower water absorption and drying shrinkage. The compressive and flexural strength of 3DPC in the printing direction were the highest, outperforming those of the cast specimens at the age of 28 days. Our results indicate that FA and GGBFS can be used to replace 50% of the cement in 3DPC.