Print-Cast Concrete: Additive Manufacturing for 3D Printing Mortar in Robotically Fabricated Green Sand Molds

Abstract

The research investigates architectural-scale concrete 3D printing in robotically fabricated recyclable molds for the fabrication of rapidly constructed, structurally optimized, architectural-scale concrete structures. The research of Print-Cast Concrete utilizes a three-dimensional extrusion path for deposition of material over a subtractive shaped sub-structure of CNC tooled compacted green sand. This process expedites the production of doubly curved concrete geometries by replacing traditional formwork casting or horizontal corbeling with spatial concrete arching deposited in relation to optimized structural loads. Creating robust non-zero Gaussian curvature in concrete, this method increases speed over typical pre-cast concrete fabrication practices, especially when producing mass customized unique elements. Through the casting component of this method, concrete 3D prints have greater resolution along the edge condition resulting in tighter assembly tolerances between multiple aggregated components. Addressing digital form finding and optimization, material behaviors, and novel utilization of robotic fabrication, this research work displays a series of key concepts within Print-Cast Concrete, advancing edge condition precision of extrusion-based 3DCP.