Multi-Scale Orthotropic Damage Constitutive Model for 3D Printed Concrete Informed by Pore Structure (2025-08)¶

The mechanical behaviour of 3D printed concrete (3DPC) is influenced by many factors, complicating the development of precise constitutive models. This study proposes a systematic approach to establish a multi-scale orthotropic damage constitutive model for high-quality 3DPC. A novel method is proposed to optimise printing parameters by analysing the geometric characteristics of the printed cross-section. Building on high-quality 3DPC, multi-scale representative volume elements are constructed. At the meso-scale, X-ray computed tomography is employed to distinguish the solid and pore phases and to quantify the pore structures. At the macro-scale, 3DPC is divided into four regions based on the statistical variations in the pore structure. The Mori–Tanaka homogenisation method is applied to determine effective elastic properties. Micro-scale damage is statistically characterised by the probability of micro-element failure, while meso-scale damage is defined through the stiffness degradation caused by oriented pores. An orthotropic damage constitutive model is formulated based on the strain equivalence principle. Experimental validation confirms that the model effectively captures the orthotropic mechanical behaviour of the 3DPC. The proposed framework provides a robust theoretical foundation for advancing the application of 3DPC in structural engineering.