on direct tensile strength measuring of anisotropic rocks

The tensile strength of the anisotropic rock-like material specimens is meastred directly in the laboratory using a new device converting the compressive loading to that of the tensile before the rock breakage. the specially prepared concrete slabs of dimensions 19 cm * 15 cm * 15 cm with a central hole of 7.5 cm in diameter are tested experimentaly. the specimens are located in the compressive-to-tensile load converting device, and tested under a compressive loading rate of 0.02 mpa/s by the universal testing machine. the cubic slab samples are made in three different configurations to have the directions of 0°, 45°, and -45° with respect to the applied loading direction. in order to compare the direct tensile strength of the concrete samples with that of the indirect measuring tests, some brazilian tests are also carried out on the concrete disc specimens prepared in the laboratory. by comparing the direct and indirect testing results of the concrete tensile strength, it can be concluded that the direct tensile strength values are somewhat lower than those of the indirect ones. the tensile strength values for the three different configurations of the concrete specimens are nearly the same.