Determine the effects of pore properties on the mechanical performances of 3D concrete printing units with experimental and numerical methods

The anisotropic performances of 3D concrete printing (3DCP) units were usually considered correlated to interlayers. While recent studies proposed that the anisotropy might be caused by pores, the link between pore properties and mechanical performances remains at a qualitative level. In this paper, Computed Tomography (CT) scans and mechanical tests were first conducted to determine the pore properties and the mechanical performances of 3DCP units. Afterward, MATLAB codes were adopted to convert CT scan images into finite element (FE) models containing pores and solid elements of concrete, and an inverse method was applied to obtain the constitutive model of concrete. Finally, CT-scan-based simulation was carried out, and the corresponding results were compared to experimental results to determine the quantitative link between the pore properties and the mechanical performances of 3DCP units. CT scan results showed that pores can be represented by a biconvex-lens shape without the obvious orientation along the printing direction, which differs from the observation in previous studies. Compared to the mechanical test results, CT-scan-based simulation results showed good agreement with a maximum error of 5.9 %, which revealed its feasibility for evaluating the 3DCP unit mechanical performances. Because the model only contains a sole variable - pores, the consistency between simulation results and test results proves the quantitative link between the pore properties and the mechanical performances of 3DCP units.