"There are considerable experimental difficulties in determining the true tensile strength of concrete. Indirect tension tests, minor misalignments, and stress concentrations in the gripping devices are apt to mar the results. For many years, tension strength has been measured in terms of the modulus of rupture for the computed flexural tensile stress at which a test beams of plain concrete fractures. Because this nominal stress is computed on the assumption that concrete is an elastic material, and because this bending stress is localized at the outermost surface, it is apt to be larger than the strength of concrete in uniform axial tension. It is thus a measure of but not identical with the real axial tension strength."