Non-destructive testing for quality and performance assessment of 3D-printed concrete elements

The industrial deployment of extrusion-based 3D Concrete Printing (3DCP) requires Quality and Performance Assurance (QPA) protocols that are both reliable and field-applicable. This thesis evaluates whether standard non-destructive testing (NDT) tools (Ultrasonic Pulse Velocity (UPV, timeof- flight metrics) and a Schmidt rebound hammer (RH)) can support QA/QC decisions for 3D-printed cementitious elements within Techint Engineering and Construction (TEPAM centre, Buenos Aires). A traceable experimental workflow was implemented to link full-scale printed walls to standardized cored cylindrical specimens, enabling one-to-one pairing between NDT indicators and destructive test outcomes. The campaign investigated two printing configurations of the layer height and nozzle bead width (30x80 and 40x50 mm), three coring orientations (XC/YC/ZC) and three extraction levels along wall height (BOT/MID/TOP), at curing ages of 14 and 28 days. Destructive testing included compressive strength and splitting tensile strength; a subset of specimens was tested at Universidad de Buenos Aires (UBA) to obtain static Young’s modulus and benchmark the applicability of code-based stiffness estimates. Results show that mechanical anisotropy is the most stable signature of the dataset, whereas wallheight gradients are not robust or systematically monotonic. A configuration-specific, interfacecontrolled failure mechanism was documented for the 30×80 family: aligned voids along inter-bead planes promoted preferential separation and increased strength dispersion. UPV velocities clustered within a narrow high-velocity band while compressive strength remained widely scattered; no stable monotonic fc-V relationship emerged, and Vmin did not provide systematic improvement. Moreover, conventional code-based E-fc relationships were found to overestimate the measured static modulus at early age. Rebound results acquired on specimen end faces (RN5) exhibited weak or subgroup-dependent trends and were therefore interpreted as an auxiliary indicator under the geometric and surfacecondition constraints of specimen-scale testing. A transparent subgroup-based correlation workflow (28-day dataset) compared UPV-only, RH-only and SonReb-type models fitted in log-space and evaluated through RMSE in MPa. The combined SonReb approach did not provide a consistent and generalisable RMSE reduction versus UPV-only across configuration–orientation subgroups, indicating limited incremental value of RN under the present setup. Overall, standard time-of-flight UPV is best framed as a uniformity and measurement-stability gate (including repeatability/COV-based flags) rather than a standalone strength predictor for 3DPC. A future roadmap is proposed toward wall-scale, standard-compliant RH/UPV campaigns, ultrasonic imaging/tomography for defect mapping, interface-representative mechanical testing (four-point bending), and vibration qualification to assess transport-induced damage.