Impact of mix proportions on particle bed 3D printed concrete properties

Abstract

Additive manufacturing of concrete using particle-bed printing by selective binder activation is examined. This technique consists of spreading of a dry powder layer onto the build platform, selective liquid deposition to form a geometry on the layer, and repetition until complete. This enables the manufacturing of complex structural elements and eliminates the need of support structures during fabrication. A commercial liquid-jet 3D printer was modified and used along with a dry mixture of sand, cement, and a specially formulated aqueous solvent. The influence of the proportions of the dry powders, water/cement ratio, type and gradation of sand, type of cements, and additives on the strength and dimensional inaccuracy is examined. The results indicate that the CSA cement with round grain silica sand provides the best mechanical performance and surface quality. The use of a sand/cement ratio of 2.0, printed water/cement ratio of 0.151, and sand fineness modulus of 2.751 produced the best mechanical strength and dimensional accuracy. The results can be used to guide the design for this innovative 3D printing approach for concrete structural elements.