Mechanical properties and behavior of 3D-printed concrete structures

The study of material properties is the preliminary stage of understanding the behavior and capacity of the material. Moreover, the material properties are also the essential input required for the prediction of the structural behavior by finite element analysis (FEA). Because of the above-mentioned reasons, the material for the 3D-printing method has also been studied worldwide. However, one of the characteristics of the 3D-printing method is the layer-by-layer formation, which leads to different behavior compared to the casting method. In addition, the printing process also stimulates the reduction in 3DP properties by the effect of printing parameters, e.g. the printing interval time and the size of the printing layer. Besides, external factors can also be an important reduction determinant, for example, ambient temperature and relative humidity. In this study, the mechanical properties of 3DP mortar, including compressive, flexural, and tensile strengths, were investigated. The specimens were prepared by two different methods: casting and printing, to investigate the effect of the fabrication process on the specimen properties. In addition, the characteristic properties of printed specimens, including the normal and shear interface properties, were also studied. The interface properties could be the weakest area of the printed specimen. Therefore, the solutions to enhance the interface properties, including chemical solutions, mechanical solutions, and chemical solutions combined with mechanical solutions, were also studied. 3D-printed components have been pervasively used as decorative items because of the benefits of limitless design. However, the attempt to apply 3D printing in the construction industry has become popular due to the challenge of labor and quality problems in construction work. However, confidence in using 3D-printed components as structural members is still not guaranteed because of the limited number of studies that depict structural behavior of the 3D-printed structural members. Therefore, to study the behavior and capacity of 3D-printed structural members, the specimens were divided into two different types of structural members, i.e., walls and beams. To investigate the effect of texture on the behavior of 3D-printed walls, the same size of walls with three different printed textures; plain, diamond, and carp patterns were prepared and tested under uniform axial compression. For the 3D-printed beams, two same-span-length tested beams with different cross sections were prepared and tested to study their different failure modes. From the results of this investigation, it can be concluded that for the testing of material properties, monolithic specimens showed high capacity than printed specimens. While the printed specimens showed large scattering test results. The increase in printing interval times significantly leads to a reduction of the interface properties. The chemical solution to enhance the interface properties shows better performance compared to others. For 3D-printed structural members, the walls with diamond texture show better performance compared to others in terms of behavior and worthiness of resource consumption. For the tested beams, different beam cross sections lead to different capacities and failure modes.