Experimental characterization and constitutive modelling of the anisotropic dynamic compressive behavior of 3D printed engineered cementitious composites

Engineered cementitious composites (ECC) offer a potential solution to the weak tensile strength and cracking issues of 3D printed concrete (3DPC), while their great performance under dynamic loading helps to broaden the application scope of 3D printing technology. This study systematically investigates the relationship between the dynamic compressive properties and the anisotropic behavior of 3DP-ECC under various strain rates through ultrasonic pulse velocity, quasi-static and dynamic compression, as well as novel sieving tests. The results indicate that the dynamic compressive behavior of 3DP-ECC shows a pronounced strain rate dependency especially in the Z-direction, while the mechanical anisotropy coefficient of the 3DP specimens decreased by 14.2% as the strain rate rose from 60 s⁻¹ to 120 s⁻¹. In what follows, the fractal theory is applied to characterize the internal damage of 3DP-ECC in different orientations, indicating that the dynamic compressive strength and dissipation energy exhibit a linear relationship with the fractal dimension. Based on the modified viscoelastic theory and spatial transformation tensor method, the anisotropic damage dynamic compression constitutive model is developed to predict the stress-strain behavior of 3DP-ECC at different strain rates. The exploration of dynamic compression behavior and anisotropic constitutive relationships of 3DP-ECC provides a basis for further integrated practical applications under extreme strain rate conditions.