Specimen size and shape effect on the compressive strength of concrete

Abstract

The results of the investigation of the specimen size and shape effect on concrete strength indicators are presented in this paper. Research on the strength of concrete specimens in the form of cubes (150x150x150 mm) and cylinders of different diameters (50 mm, 100 mm and 150 mm) and heights (100 mm, 200 mm and 300 mm), under compression are carried out on Matest testing machine with Servo-Plus Evolution servo-drive control unit. Three specimens of each type are tested. Control specimens are made according to such ratios of materials that concrete corresponds to the strength class C16/20. All specimens are visually inspected for the presence of any defects, such as large pores, chips, or shrinkage cracks. After that, the actual measurements of all specimens are carried out. They showed minimal deviations from the planned size, which is considered acceptable. In order to check the reliability of the results, after the research of each type of specimen, calculations are carried out to determine the actual strength and the concrete grade. The actual dimensions of the faces and the results of the certain batch research are taken. The data obtained from the concrete specimens research on the test press are analyzed. Due to the formulas and data obtained after the investigation, the actual strength class of concrete for all specimens is determined. According to the results of the research, fracture graphs of all types of control specimens are constructed. The results show that the laboratory measurements are consistent with the literature results, namely that the compressive strength decreases with the specimen size increase. In the case of the smallest, non-standardized specimens (cylinders with 100 mm height and 50 mm diameter), the deviation of compressive strength tests is higher compared to other specimens. The graph is presented for visualizing the specimen type and size effect on concrete strength.