Study on preparation and mechanical properties of 3D printed concrete with different aggregate combinations

3D printed concrete (3DPC) properties are closely related to the characteristics of coarse aggre-gates and fine aggregates. In this paper, the role of recycled aggregates in 3DPC is considered and the printable inks with different aggregate combinations were well prepared. The mechanical properties of 3DPC containing different aggregates were compared and analyzed, and the effect of recycled aggregates on the development of concrete properties was further investigated under different curing conditions. The results showed that the full recycled aggregate reduced the 3DPC interlayer deformation by 3.1 mm at a height of 120 mm, and the minimum anisotropic compressive strength of it was 16.36 MPa, approximately 67.15% of that of the cast-in-place one. And compared to the full replacement of recycled coarse aggregates, the full replacement of recycled fine aggregates in air curing facilitates the improvement of the mechanical properties of the concrete, with an increase of 4.1 MPa at 28d, but with a negative impact in standard curing. In addition, the reduction in mechanical properties with the combination of fully recycled coarse and fine aggregates is less than the sum of the reduction with the single aggregate, under any type of maintenance or pouring.