Multi-scale characterization of the 3D printed concrete strength considering the full grade pore structure

The macro-mechanical characteristics of 3D printed concrete (3DPC) are impacted by the porous interfaces from both filaments and interlayers. Under the consideration of a full pore size characterization, the variations on pore size-volume are investigated in the spatial distribution of the micro-, meso-, and macro-scales. The introduced pores affect the distribution density and geometric characteristics of hydrated pores. An active regulation of introduced and hydrated pores after hardening is achieved by microbial healing method, which affects the spatial distribution of the gel pores, capillaries and printed voids. The results indicate that the anisotropic compressive strength of concrete is correlated with distribution and number of pores in a size range between 20 nm and 3mm. A pore-strength model for 3DPC is developed and analyzed based on Powers theory, to simulate the effects of spatial distribution in stacked interfaces. In addition, the 3DPC constitutive stress-strain relationship with three mixing ratios considering the pore shapes and spatial distributions are established and evaluated.