Evaluation of Mechanical Anisotropy-Induced by 3D Printing Process for Earth-Based Materials (2023-07)¶

Due to the high energy consumption of cement-based materials, debates are increasing to develop new composites using natural resources. As a result, there are more investigations on bio-based and earth-based materials in the literature thanks to their capability to reduce carbon dioxide gas emissions (CO2). Accordingly, earth has a strong potential since it hardens by drying rather than by hydraulic setting, it is also infinitely repairable and recyclable, without generating greenhouse gas. This work investigates the manufacturing of earth-based material using 3D printing process. In the first step the water content was found according to the rheological criteria target allowing the material to be extruded at a continuous and regular flow rate. The corresponding dosage ensures a sufficient yield stress allowing the deposit of the printed layers without collapsing and the possibility to support the upper layers. In the second step, prismatic specimens were printed using two different nozzle outputs. The samples were cut and sanded to extract normalized specimens. After mass stabilization, mechanical tests were conducted, the work included three-point bending tests, compression tests and shear tests. The findings were compared with the results obtained on cast specimens. As printed elements are made layer after layer, the manufacturing method had an impact on the behavior, the quality of the material and exhibited an apparent anisotropy. Consequently, for each test, the loading was applied in the longitudinal, transverse, and normal directions regarding the printed layers. It has been found that the resistances of the printed samples were of the same order of magnitude as those measured on cast ones, especially when the loading was perpendicular to the printed layers. On the other hand, the resistances were significantly reduced when the loading led to expansion or tension perpendicular to the layers.