Investigate mechanisms of different printing parameters on the mechanical anisotropy of 3D concrete printing elements by using computed tomography scan and computational fluid dynamics methods

3D concrete printing (3DCP) elements show significant mechanical anisotropy. Printing parameters can affect the mechanical anisotropy of 3DCP elements. However, most studies have focused on the effects of printing parameters on the interlayer bond strength at a macroscale level. The mechanisms of printing parameters on the mechanical anisotropy of 3DCP elements remain unclear. To fill research gaps, computed tomography (CT) scans, computational fluid dynamics (CFD) numerical simulations, and uniaxial compression tests (UCTs) were conducted with the printing parameters of the expansion state of the nozzle flow channel, overflow ratio, stand-off distance, and flow rate involved. The results of CT scans, CFD simulations, and UCTs revealed the mechanism that the printing parameters affect porosity distribution and pore anisotropy by influencing the normalized local pressure at interlayer and fluid velocity gradients, respectively, which further results in the modification of the mechanical anisotropy of 3DCP elements.