Hybrid Approaches Towards 3D Concrete Printing for Lightweight Reinforced Concrete Structures

3D Concrete Printing (3DCP) has paid little attention to producing material-efficient parts. Material optimization methods, such as topology optimization, often result in forms with complex geometries—extreme overhangs and multi-branching—that are challenging to achieve in large-scale 3DCP. The limited studies on 3DCP of topology-optimized forms often (a) use excessive supporting material, resulting in waste, or (b) discretize topology-optimized forms into simpler components that are later assembled, leading to labor-intensive assembly and accuracy errors. This research seeks to enable the 3D concrete printing of such structures in a streamlined process, eliminating the need for discretization and support materials. To prevent collapse during the 3D printing of extreme overhangs, we explore a method that combines 3DCP with the simultaneous casting of fast-setting concrete materials. For precise concrete deposition that accurately follows the contours of a shape, we introduce topology-informed non-planar printpath and a variable material deposition rate. The method is investigated through a construction scale load-bearing wall, Branch Wall, with steep cantilever branches and in-between thin surfaces and a series of S-Shape specimens (230 mm diameter and 500 mm height) produced through simultaneous 3DCP and casting of fast-setting concrete.