Multi-axial 3D printing of biopolymer-based concrete composites in construction

This paper explores the free-form potential of 3D concrete printing, enabled by a novel concrete-like composite made from 80 %-w/v mammal gelatin solution in water with 35 %-w/w gelatin solution to mineral aggregate ratio. This complete replacement of cementitious binders in 3D printing mortar aims on improving the sustainability and advancing the setting control through the material's thermoplasticity. The material was extruded with a novel and heated ram extruder, traversed with a KUKA robot arm, and cooled by a box fan under normal ambient temperature and humidity conditions. Printing trials with cylinders of 20 cm diameter and various overhang inclinations were carried out – both vertically and multi-directionally sliced. The overhang was increased until the fresh material could no longer support itself. The multi-directionally sliced objects showed the largest overhang capabilities. The thermoplastic printing mortar was able to print a maximum overhang of 80°. This demonstrated freedom of shape and applicability of the bio-based mortar to a 3D printing process could pave the way for highly optimized building components with a minimum use of material. This can incre the sustainability aspects of concrete structures.