Toward Sustainable Clay-based Additive Manufacturing: Fresh-State and Hardened Mechanical Characterization of 3D-Printable Benjellik Clay Paste

Introduction/Objective Additive manufacturing (AM), particularly 3D printing, has revolutionized material processing by enabling complex geometries with high precision and minimal waste. While Fez-Moroccan clays (specifically from the Benjellik quarry) have been thoroughly characterized for their mineralogical and physicochemical properties, their mechanical behavior - essential for assessing buildability and structural integrity in printed structures - remains poorly understood. This study aims to address this limitation by evaluating the mechanical performance of a 3D-printable clay paste. Methods A comprehensive experimental framework was implemented to assess key mechanical properties of the clay paste. Measurements included Young’s modulus, yield stress, and strain evolution; analysis of drying-induced shrinkage behavior; assessment of fracture modes; and evaluation of how different infill patterns influence compressive strength. Results The clay paste, formulated at a water-to-binder ratio of 37.5%, exhibited drying-time-dependent mechanical behavior over a 21-day period. Young's modulus and compressive strength increased asymptotically to 130.6 MPa and 2.98 MPa, respectively, while peak strain decreased from ~15% in the fresh state to 3.35% at full drying. Maximum shrinkage ratios reached 26.7% for mass and 14.5% for width. ANOVA confirmed that drying time was the dominant factor governing all mechanical properties ( p < 0.001), while infill pattern (grid-like vs . cross-hatch) exerted no statistically significant effect ( p > 0.05). Discussion These results highlight that print parameters must be carefully tailored to the specific rheological properties of the raw material to prevent structural failure. The sensitivity to moisture and infill density underscores the need for process control in clay-based 3D printing, bridging material science with digital fabrication for sustainable construction applications. Conclusion These findings provide a quantitative mechanical framework for 3D-printable Benjellik clay paste, supporting its use in sustainable additive manufacturing applications and offering model parameters directly applicable to buildability assessment.