3D printed concrete produced from an identical mixture exhibits distinct compressive strengths under different printing paths. This anisotropy originates from printing-induced pore alignment that alters load transfer. Scalar porosity and qualitative interlayer descriptors lack loading-direction resolution and cannot capture direction-specific strength penalties or in-plane strength re-ranking. To address this gap, a loading-direction-resolved pore directional index is developed to link pore elongation, area weighting, and orientation to direction-specific defect severity. Specimens produced with four representative printing paths and a cast control are investigated using a fixed mixture. Directional compressive strengths along x , y , and z are quantitatively linked to pore structure on x – z and y – z sections. This mechanism is validated using image-informed finite-element models of reconstructed pore-scale representative volume elements subjected to directional compression. The simulated strength ratios agree with experiments, with maximum relative errors of 13.69% ( x–z ) and 9.42% ( y–z ), demonstrating that pore structure controls printing path-dependent anisotropy.
Cheng et al. (2026) studied this question.