NDT Techniques for Evaluating Mechanical Properties in Green and Fiber-Reinforced 3D Printable Mixes (2025-08)¶

Non-Destructive Testing (NDT) techniques play a vital role in assessing the structural integrity and durability of 3D-printed concrete, allowing damage-free evaluation and ensuring compliance with industry standards. The inherent porosity in 3D-printed concrete, resulting from its layer-by-layer deposition, presents challenges to long-term performance. This research examines the combined effects of ground granulated blast furnace slag, Alccofine 1203, and polypropylene fibres in reducing porosity and improving structural properties. The mercury intrusion porosimetry test indicates a 19.07% reduction in porosity for the fibre-reinforced printed elements, while their internal structure is 28.75% more tortuous than that of unreinforced printed elements. NDT methods, including ultrasonic pulse velocity, rebound hammer, and water absorption tests, along with destructive rapid chloride penetration tests, offer both qualitative and quantitative insights into the performance of the printed elements. Experimental results show that the M8 mix exhibited a reduction in charge passed compared to the M4 mix by 5.29% in the X direction, 4.67% in the Y direction, and 2.41% in the Z direction, indicating improved chloride ion resistance across all orientations. UPV results closely match compressive strength trends, with R² values of 0.96 (without fibre) and 0.98 (with fibre). Mix M8 (G20A8F0.2) exhibited superior mechanical and durability performance.