Abstract:
Additive manufacturing reshapes concrete construction, yet routine strength verification of
printed elements still depends on destructive core sampling. This study evaluates whether
standard 70 mm cubes—corrected by a single factor—can provide an equally reliable
measure of in situ compressive strength. Five Portland-cement mixes, with and without
ash-slag techno-mineral filler, were extruded into wall blocks on a laboratory 3D printer. For
each mix, the compressive strengths of the cubes and ∅ 28 mm drilled cores were measured
at 7, 14 and 28 days. The core strengths were consistently lower than the cube strengths,
but their ratios remained remarkably stable: the transition coefficient clustered between
0.82 and 0.85 (mean 0.83). Ordinary least-squares regression of the pooled data produced
the linear relation Rˆ
core [MPa] = 0.97 Rˆ
cube − 4.9, limiting the prediction error to less than
2 MPa (under 3% across the 40–300 MPa range) and outperforming more complex machinelearning models. Mixtures containing up to 30% ash-slag filler maintained structural-grade
strength while reducing clinker demand, underscoring their sustainability potential. The
results deliver a simple, evidence-based protocol for non-destructive strength assessment
of 3D-printed concrete and provide quantitative groundwork for future standardisation of
quality-control practices in additive construction.
