Investigating the impact of coarse aggregate dosage on the mechanical performance of 3D printable concrete

The effect of the addition of coarse aggregate on the direction-dependent mechanical performance of 3D printed mortar has been investigated. Coarse aggregates in the size range of 4.75–9.5 mm were manually added during printing into 3D printed mortar in 5, 10, and 15 (wt.% of mortar) dosages. The spilt tensile test indicates that the strengths of 3D printed mortar containing coarse aggregate are direction-dependent due to modified interlayer properties. The results of this study indicated an improved bonding effect in 3D printed mortar due to cross-layer nesting of the aggregates. The effect of coarse aggregate addition resulted in up to 32 and 19% increase in split tensile strength in Z- and Y -loading directions, respectively, compared to casted specimens. However, coarse aggregate weakens the split tensile strength in X -direction loading, whereas compressive and flexural strengths both commonly decrease with increasing aggregate dosage after an optimum dosage of aggregate addition due to their anisotropic characteristics.