Experimental Study on Mechanical Properties of 3D-Printed Specimens of Iron Oxide, Quartz, and Bedded Composites Under Uniaxial Compression and Indirect Tensile Strength

The heterogeneity of natural rocks produces increased variations in the results of geomechanical and metallurgical tests making the repeatability of experimental work questionable. Fabricated test specimens have, therefore, become more attractive for fundamental studies. In this study, quasi-identical 3D-printed (3DP) specimens with 10 and 16 mm diameters were fabricated and tested to study material strength and understand the breakage characteristics at a scale more suitable for comminution. Cylinder specimens composed of quartz (named Si) and iron oxide (named Fe), with sorted grains of ∼100–150 μm in the form of homogeneous specimens (3DP-Si and 3DP-Fe) and heterogeneous specimens (bedded) (3DP-SiFeSi, 3DP-SiFe, and 3DP-FeSiFe) were tested. This article presents the results for experimental Unconfined Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The elastic property was obtained from the UCS tests, while tensile strength was obtained from BTS tests. The strength of 3DP specimens of similar diameter decreases following the types: 3DP-Si (most competent), 3DP-Si-Fe, 3DP-SiFeSi, 3DP-FeSiFe, and 3DP-Fe (less competent). The results show that heterogeneous 3DP specimens were influenced by bedding angle, thickness, and mineral group composition. It also seems that the sequence of mineral composition and the number of beds play a role, rather than the overall grain percentage area for each cylinder, in influencing the strength and variability of fragments. Finally, the brittleness indices for 3DP specimens were calculated as a function of UCS and BTS.