Effect of sand gradations on the fresh properties of 3D printable concrete

Sand is frequently used as a fine aggregate in concrete mixtures, however, the performance of concrete can be considerably impacted by regional variations in sand gradation. This study systematically investigated the effect of sand gradations on fresh properties of 3D printable concrete (3DPC) mixtures. The binder combinations, including cement, fly ash, silica fume, limestone powder, ground granulated blast furnace slag, and the water-to-binder ratio, were constant throughout the trials. The mini-slump height and flow values of optimal packing of binary and ternary combinations of standard Ennore sand (Grade I, Grade II, Grade III) compared to locally available river sand and the unary packing of Ennore sand and river sand. In addition, the correlation between the fineness modulus of different sand gradations and printable flow time were determined. The influence of sand gradations and fineness modulus on buildability, shape retention, open time and extrudability were evaluated. The findings demonstrated that the performance of the fresh 3DPC is influenced by the aggregate's gradation and grain size in addition to its fineness. In conclusion, different fine aggregate specifications must be chosen depending on the various 3D printing building conditions and design requirements.