Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150796

150796 - Developing 3d-Printed Natural Fiber-Rich Earth Materials in Construction 

This research investigates the advancement of 3D printing technology applied to clay and earth-based materials, focusing on the enhancement of these materials with natural fiber reinforcements. The integration of natural fibers such as wheat straw, hemp, banana, and kenaf into 3D printable earthen composites is explored to improve mechanical performance, durability, thermal resistivity, and carbon storage potential. This study, conducted by a team from Columbia University's Graduate School of Architecture, Planning and Preservation and the Department of Civil Engineering and Engineering Mechanics, seeks to define optimal mix designs and evaluate the mechanical performance and ductile behavior of these composites through rigorous testing.

The research highlights the necessity of fiber reinforcement in 3D printable earth materials to overcome the limitations of current examples, which often lack sufficient thermal conductivity and ductility. Traditional knowledge in earth- and fiber-based construction, such as light straw clay, serves as an inspiration due to its historical use for insulation. This study pioneers the development of 3D printable fiber-based clay mixtures, focusing on the characterization of printability and bending strength parameters.

The materials and methods section details the selection and preparation of fibers and soils used in the study. Four types of fibers were analyzed: wheat straw, hemp, banana pseudostem fibers, and kenaf. The soil, a red clay-sand composition, was sourced from a compressed earth block manufacturing facility in Colorado. The research incorporated food-grade additives such as methylcellulose, sodium alginate, and locust bean gum to stabilize the mixtures.

Two mixing methods, manual and machine-assisted, were employed to prepare the 3D printed specimens. The study found that machine mixing significantly improved the homogeneity and mechanical properties of the composites compared to manual mixing. The 3D printing process utilized a PotterBot 4 Pro with a 6mm nozzle, and the specimens were dried in a controlled environment to ensure consistency.

Bending strength tests were conducted according to ASTM C67 standards using the MTS Criterion 7k Universal Testing Machine. The results demonstrated a notable increase in bending strength for machine-mixed samples compared to manually mixed ones. Specifically, machine-mixed composites showed a 29-78% improvement in bending strength, highlighting the importance of controlled mixing methods in maximizing the potential of fiber-reinforced earth materials.

The study concludes that the method of paste preparation significantly influences the workability and scalability of the material. Machine mixing offers the potential for larger-scale applications, reducing labor constraints associated with manual mixing. The research underscores the need for further investigation into the effects of water content reduction and the impact of geometrical patterns and printing paths on bending strength and environmental impacts.

Overall, this study represents a significant advancement in the development of sustainable, low-carbon building materials. The incorporation of natural fibers into 3D printable earth composites not only enhances their mechanical properties but also contributes to the broader goals of creating healthy, equitable, and environmentally responsible buildings. This research lays the groundwork for future innovations in 3D printed construction materials, emphasizing the importance of fiber reinforcement and advanced manufacturing techniques in achieving sustainable building solutions.

Presenting Author: Eunjin Shin Columbia University

Presenting Author Biography: E.J. Shin recently received her Master of Architecture degree from the Graduate School of Architecture, Planning, and Preservation at Columbia University. She is currently pursuing a Master of Science in Civil Engineering at the Fu Foundation School of Engineering and Applied Science, also at Columbia University.

E.J.'s experience in the built environment spans a broad spectrum. She has supported the construction of the Tappan Zee Bridge Hudson River Crossing, New York State’s signature bridge, and participated in the international exhibition at the Venice Biennale of Architecture.

She is a recipient of the Percival & Naomi Goodman Fellowship and a 2024 CRIT Scholar in partnership with the American Institute of Architects (AIA).

Authors:

Eunjin Shin Columbia University
Olga Carassi Columbia University
Yierfan Maierdan Columbia University
Shiho Kawashima Columbia University
Lola Ben-Alon Columbia University