Pre-installed Reinforcement for 3D Concrete Printing

Abstract

Providing reinforcement is essential for the structural integrity of concrete elements and for safely handling, transporting, and assembling prefabricated concrete parts. However, the integration of reinforcement is a persisting challenge in 3D concrete printing with extruded concrete. This paper presents a production process consisting of 3D printing around pre-installed reinforcement. The reinforcement is composed of conventional reinforcing steel bars, which can be pre-assembled in cages independently of casting, boosting the specialisation and efficiency in production. This approach was used to produce a 3.4 m span T-beam with optimised topology, consisting of three segments connected with matching surfaces. The beam segments were printed upside down, with an open web on top of the flange. Each segment featured reinforcing steel installed in the flange and web. After printing and assembling the segments, a conventional reinforcing bar was inserted in the web as bending reinforcement and grouted subsequently. The structural performance was assessed in a six-point bending test. The fabrication and structural testing of this case study beam showed that pre-installed reinforcement imposes several challenges to the extruder precision, the precision of the bent reinforcement, and – if applied – the casting after printing.