Mechanical and Thermal Properties of 3D Printed Earth Concrete Solidified by Geopolymers (2025-04)¶

Earth concrete (EC) is a low-carbon and green building material. However, its widespread application is limited due to low strength, low water resistance, and high labor density. In this work, a combination of 3D printing and geopolymer was utilized to solidify excavated clay, and 3D printed earth concrete (3DPEC) was prepared. Firstly, the flowability, consistency, and buildability of 3DPEC were tested to demonstrate the feasibility of EC for 3D printing. Secondly, a quantitative evaluation was conducted on the anisotropic flexural strength, compressive strength, and stacked and adjacent interlayer bonding strengths of 3DPEC. It was found that geopolymer solidification can significantly improve the compressive strength and flexural strength of EC, with a maximum increase of 2378% and 3448%, respectively. Computed tomography (CT) was used to analyze the pore structure and distribution of 3DPEC. The analysis revealed that solidification significantly inhibits cracks and reduces porosity, especially decreasing the number and proportion of pores with a volume greater than 1 mm3. The thermal conductivity of 3DPEC was analyzed using the transient hot wire method. The thermal conductivity of 3DPEC was increased by 43.7% after solidification, but it was about 9.6% to 10.4% lower than cast EC. Therefore, 3DPEC has potential applications in low-rise buildings, attributed to its satisfactory mechanical and thermal properties and low environmental impacts.