Influence of Recycled Aggregates on fresh and hardened properties of 3D printable concrete mix

This study investigates the effects of adding up to 50% virgin or recycled aggregates, with maximum diameter of 10 mm, in cementitious mortars for 3D concrete printing. Fresh mixture properties and mechanical performances (dynamic elastic modulus, flexural and compressive strength at 1, 7, and 28 days) were evaluated. Although mixes with virgin aggregates showed higher strengths, replacement with 50% recycled aggregates did not lead to significant reductions in mechanical properties, with 28 day compressive strengths exceeding 55 MPa. While extrusion and surface finish posed challenges at 50% aggregate content, good workability (130-132 mm spread diameter, comparable to commercial mixes) and buildability at 30% aggregate content indicate strong potential for this application.