The presence of the interfacial transition zone (ITZ) between aggregates and the mortar matrix in concrete has been studied extensively. A numerical and experimental study involving concrete specimens with multi-inclusions was conducted, and the ITZ was modeled as a cutoff bar in the finite element analysis, representing the shear and tensile behavior. The mortar specimens were sized 100 mm by 100 mm, with a thickness of 50 mm, and the inclusions were cylindrical aggregates with a diameter of 20.85 mm. The specimen was loaded in uniaxial compression. Two inclusion axes configurations were considered: parallel and perpendicular to the line of loading. The finite element analysis was performed assuming a 2D behavior. Further, the aspect of the distance between inclusions was studied. It was shown that, in general, the perpendicular arrangement resulted in a significantly higher compression strength when compared to the parallel formation. For both the parallel and perpendicular configuration, the relationship between the increase in the axis distance and the compression strength followed a quadratic path. First an increase in strength was observed, followed by a reduction, as the axis distance evolved. Additionally, it was shown that the ITZ area in tension initiated the failure of all specimens.
