3D printing for construction: development of earth-based matrices stabilized with chitosan biopolymer and reinforced with natural sisal fibers

Abstract

In the last few years, 3D printing with robots or automated equipment has emerged as a technology with significant potential in the construction sector. This approach offers several advantages, including reduced construction time and costs, design flexibility, and the ability to use various materials. Earth, as a building material, has gained attention in 3D printing due to its eco-friendliness compared to cement. However, it remains relatively underexplored in this industry. Unfortunately, earth is known for its poor mechanical strength, water durability, and susceptibility to swelling, especially due to its clayey composition. These factors can lead to cracking during the drying process. To address these challenges, researchers have been investigating different materials for 3D printing, aiming to minimize the ecological footprint by using biodegradable materials or repurposing waste for stabilization. Recent studies have explored the use of biopolymers such as chitosan, alginate, and potato starch to enhance the mechanical and durability properties of earth-based mixtures. Additionally, the incorporation of natural fibers like sisal or jute has proven effective in reducing cracking in earthen structures. Considering the above, it would be advantageous for the construction industry to employ 3D printing to produce earth-based matrices stabilized with biopolymers and reinforced with natural fibers. Designing such matrices requires an approach that accounts for the yield stress suitable for 3D printing, ensuring the mixture possesses key printability characteristics such as extrudability, workability, and buildability. The evaluation of these properties in the fresh state, during hardening, and in the hardened state necessitates conducting various tests recommended by international standards and researchers. In order to outline a procedure for obtaining a printable matrix that meets the desired mechanical strength and water durability, a methodology is proposed for developing earth-based matrices stabilized with chitosan and reinforced with sisal fibers. This methodology consists of three stages. The first stage involves conducting physical, mechanical, chemical, and mineralogical analyses of the raw materials: soil, chitosan, and sisal fibers. The second stage encompasses an optimized procedure to obtain potentially printable earth-based matrices through laboratory testing using a pastry bag. Finally, the validated earth matrix from the previous stage undergoes 3D printing to create different specimens, allowing for the evaluation of extrudability, pumpability, buildability, and mechanical strength of the mixture. The printing process utilizes a motion-controlled gantry robot with three degrees of freedom in a printing area with a volume of 1.0 m³ and employs a progressive delivery system.