Influence of Fine Recycled Aggregates on the Properties of 3D Printing Concrete (2025-06)¶

3D printing with recycled concrete aggregate (RCA) is an emerging innovation in sustainable construction and additive manufacturing. Incorporating these RCA into printing mixes contributes to more sustainable structures, reducing environmental impact and promoting the circular economy. This study investigated the effect of replacing natural aggregates (NA) with RCA in different percentages (25%, 50%, 75%, and 100%) in conventional and High Performance-strength Concrete. In the fresh state, workability was assessed by means of flow and slump tests. The results indicated that 3D printed Concretes produced using a higher content of RCA in substitution of NA achieved lower workability, which was compensated by increasing the superplasticizer content. For hardened properties, standard prismatic specimens and 3D printed specimens were produced for each RCA content mixture. Physical and mechanical properties, as well as the drying shrinkage values, were determined in each of the mixtures. The results showed that compressive strength decreased as the RCA replacement percentage increased, which is associated with higher shrinkage, absorption, and lower density. In addition, the 3D-printed specimens achieved lower compressive strength than that of standard specimens in the corresponding mixture.