The Theory of Critical Distances to assess the effect of cracks/manufacturing defects on the static strength of 3D-printed concrete

•Strength of 3D-printed concrete containing cracks/defects is investigated experimentally.•3D-printed concrete is modelled as a linear-elastic, homogenous, and isotropic material.•Critical distance methods are used to assess static strength of 3D-printed concrete.•The proposed assessment methods can be used in conjunction with commercial FE codes. The present paper deals with the use of the Theory of Critical Distances to model the detrimental effect of cracks and manufacturing defects in 3D-printed concrete subjected to static loading. The robustness of the proposed approach was assessed against a number of experimental results that were generated by testing, under three-point bending, 3D-printed rectangular section specimens weakened by saw-cut crack-like sharp notches, surface roughness (due to the extrusion filaments) and manufacturing defects. The sound agreement between experiments and predictive model allowed us to demonstrate that the Theory of Critical Distances is not only a reliable design approach, but also a powerful tool suitable for guiding and informing effectively the additive manufacturing process.