Compressive failure and size effect in plain concrete cylindrical specimens

Size effect under tensile loading for heterogeneous granular materials is well known and widely studied in the scientific literature. On the contrary, very few experiments have been performed in compression, which, especially for concrete, is more important considering its structural applications and the fact that the compressive failure, in absence of an effective confinement, represents a significant brittle failure mode. In this paper the results of an experimental investigation on cylindrical (column-like) specimens of plain (un-reinforced) concrete under uniaxial compressive loading with a large size range of 1:8 are presented. The diameter of the tested specimens ranges from 100 mm to 800 mm whereas their height from 200 mm to 3200 mm with three different slenderness ratios of 8, 16, and 32. It has been observed that for all slenderness ratios the nominal strength exhibits a strong size effect. Finally, the results are compared with some size effect laws and other experimental data. Based on theoretical consideration the most appropriate size effect law for concrete under compression is also suggested.