Internal optimisation of 3D printed concrete structures

Abstract: Extrusion-based 3D concrete printing (3DCP) is a promising technique for fabricating complex concrete elements without the need of a formwork. This approach offers advantages like cost reduction and enhanced design flexibility by decoupling manufacturing costs from part complexity. By placing material only where is structurally needed, 3DCP enables significant material savings, potentially reducing the environmental footprint of the construction industry. However, this extended formal freedom is still constrained by the fabrication process and material properties. This paper presents a novel method for applying topology optimisation internally i.e., respecting the external boundaries of the concrete element while reducing the material use and weight. This method adapts the thickness of the extrusion along the part according to the expected stresses, reducing the material use while maintaining or enhancing the structural performance. To validate the effectiveness of this method, the mechanical behaviour of three different unreinforced 3DCP beams is tested in three-point bending. The results show that the optimised pattern presented a higher strength-to-weight ratio than the conventional 3D printed beam. An important advantage of this proposed method is that it does not require specialised equipment and can be easily implemented in existing 3DCP systems. This paper demonstrates the potential of internal topology optimisation for improving the efficiency and sustainability of 3DCP.

Supervisors: Johan Silfwerbrand (Civil and Architectural Engineering), Helena Westerlind (Architecture)