Printability and Structural Integrity of Fiber-Reinforced Earth-Based Materials for 3D Printing

The integration of 3D printing technology in construction is gaining attention for its potential to use sustainable, earth-based materials. This study investigates the printability, mechanical performance, and durability of 3D-printed earth mixtures composed of locally available soil, sand, biopolymers, and fibers (polypropylene and hemp). Experiments examine how composition and proportions affect performance to optimize these mixtures for 3D printing. A multi-scale characterization method is employed. Index properties such as liquid limit, plastic limit, particle size distribution, optimum moisture content, and maximum dry density are measured. Rheological properties, including setting time and viscosity, are evaluated using the Vicat apparatus and rotational rheometer to assess workability and extrudability. Printability is analyzed via extrusion quality and buildability, focusing on discontinuities and deformation. Results show that biopolymer and water content, along with fiber reinforcement, significantly impact printability. Notably, the CSXP2 mixture-comprising 1% Xanthan gum and 0.5% polypropylene fiber at a water-to-dry ratio of 0.635, emerged as the optimal formulation. This mixture demonstrated consistent extrusion with an average width of 10.13 mm, green strength of 39%, fulfilling the criteria for both extrudability and buildability. Overall, the findings underscore the potential of carefully engineered biopolymer–fiber–soil mixtures to enable sustainable, durable 3D-printed earthen construction.