Assessment of Printability of Concrete based on Packing of Aggregates

The fluidity of concrete is a key parameter that determines the printability of the mixture in an extrusion-based printing process. The printability of concrete is influenced by the relative proportions of aggregate and paste, paste rheology and the aggregate properties. The complex relationship of the aggregate packing and paste content in excess to the demand and the printability of the mixture is explored using concrete made with two different types of aggregate, which have different packing densities. The paste content requirement for printable concrete mixture varies with aggregate packing and gradation. The mixtures made of aggregate with a higher maximum packing density are printable with a lower paste requirement. The printability of concrete is identified with respect to aggregate packing and excess paste content. Concrete mixtures of the same paste rheology are printable at the same excess paste content irrespective of the aggregate packing densities.