A review on 3D printing with clay and sawdust/natural fibers: Printability, rheology, properties, and applications

This review discusses the opportunities and challenges of 3D printing using clay and natural fibers with a focus on wood sawdust in direct ink writing (DIW) method. Using earthen and natural materials promotes sustainable and affordable construction. Additive manufacturing also offers low-cost and fast construction and facilitates the transition towards automated and customized practices. Considerations in preparing print slurry using clay and sawdust/natural fiber are presented. The key rheological tests and criteria to assess the printability and characteristics of fresh printing slurry are discussed. Printability of fresh slurry is explained with a focus on flowability, extrudability, and buildability. Additionally, the mechanical properties of 3D-printed clay composites reinforced with natural fibers are reviewed. The review shows the complex role of using wood sawdust and natural fiber in clay 3D printing. While such an addition may compromise the strength properties of clay composite, it improves the shrinkage and cracks following print task. The study concludes that post-printing performance shall be linked to proper design of print slurry via rheological characterization techniques. Further research is required to establish the fresh ink printability criteria. These criteria should account for rheology of fresh slurry, different loading scenarios of in-service printed structure, and geometrical complexities and requirements of final product. To fully leverage the power of 3D printing in customized fabrication and construction, additive manufacturing can be practiced by focusing on aesthetic and architectural design. Clay 3D printing can also be integrated with computational design to fabricate building structures with exterior (façade) and/or interior applications.