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Concrete produced by 3D printing has been widely studied, however, most studies focus on the static properties of 3D printed materials, but few on dynamic properties. In this study, the dynamic properties of 3D printed cement mortar were evaluated from the dynamic compressive strength, energy dissipation density, failure modes, fragment distribution, and fractal dimension. In the strain rate range of 70 s−1-140 s−1, the anisotropy of dynamic compressive strength diminishes with increasing strain rate, but remains more significant than the anisotropy of static compressive strength. Acoustic indices were used to evaluate the anisotropy of the dynamic compressive strength of 3D printed cement mortar, revealing an exponential relationship between ultrasonic pulse velocity (UPV) and dynamic compressive strength. The energy dissipation density under the same strain rate varies in three key printing directions. Finally, the number of main cracks is different in three printing directions in the failure process under the same strain rate, which leads to different degrees of damage, and thus different fragment distributions and fractal dimensions therein. [ABSTRACT FROM AUTHOR]

Comparing with the traditional construction process, 3D printing technology used in construction offers many advantages due to the elimination of formwork. Currently, 3D printing technology used in the construction field is widely studied, however, limited studies are available on the dynamic properties of 3D printed materials. In this study, the effects of sand to binder ratios and printing directions on the fractal characteristics, dynamic compressive strength, and energy dissipation density of 3D printed cement mortar (3DPCM) are explored. The experiment results indicate that the printing direction has a more significant influence on the fractal dimension compared with the sand to binder ratio (S/B). The increasing S/B first causes an increase and then results in a decline in the dynamic compressive strength and energy dissipation of different printing directions. The anisotropic coefficient of 3DPCM first is decreased by 20.67%, then is increased by 10.56% as the S/B increases from 0.8 to 1.4, showing that the anisotropy is first mitigated, then increased. For the same case of S/B, the dynamic compressive strength and energy dissipation are strongly dependent on the printing direction, which are the largest printing in the Y-direction and the smallest printing in the X-direction. Moreover, the fractal dimension has certain relationships with the dynamic compressive strength and energy dissipation density. When the fractal dimension changes from 2.0 to 2.4, it shows a quadratic relationship with the dynamic compressive strength and a logarithmic relationship with the energy dissipation density in different printing directions. Finally, the printing mortar with an S/B = 1.1 is proved to have the best dynamic properties, and is selected for the 3D printing of the designed field barrack model. [ABSTRACT FROM AUTHOR]