Automated Multi-Material Additive Manufacturing: An Initial Exploration with Concrete

Abstract

Additive manufacturing of concrete has seen an increase of interest in recent years given its potential to revolutionize the construction industry by circumventing the geometric constraints of traditional fabrication techniques while achieving improved mechanical properties and reducing construction time and cost. A well-known limitation of the material is its weak tensile strength, often requiring concrete structures to be reinforced in order to meet design standards. However, most concrete 3D-printing research to date has focused on single-material systems that do little to augment the material's mechanical properties. This work represents an initial attempt to address these concerns by detailing the development of a desktop-scale multi-material cement paste 3D-printer that combines cement paste (without aggregates) with other materials in situ to the printing process to form cementitious multi-materials. This was achieved by building a tool-changing 3D-printer that is capable of switching between different print heads and materials by following toolpaths generated with a software workflow that only needs high-level parametric inputs from the user. This device was then used to develop several multi-material architectures which were tested in bending according to ASTM standards. They showed improved overall toughness, modulous of rupture, and fracture toughness compared to cast and single-material 3D-printed cement paste components, validating multi-material cement 3D-printing as a viable way to fabricate cementitious components with improved mechanical properties.