Size effect and fracture energy studies using compact compression specimens

The size effect has been investigated and fracture energy, G(F), determined for a range of different strength concretes. The test specimen geometry used in the study was a compact compression prism. Five sizes of geometrically similar specimens with increasing square cross-sectional area (length = depth) and constant thickness (100 mm) were used in the experimental work; the length/depth dimensions of the test specimens were 100, 150, 200, 300, and 400 mm, giving an overall size range ratio of 1:4. The grades of concrete used in this study were C50, C70, C80 and C90, and the maximum coarse aggregate (crushed limestone) size was 10 mm. A strong size effect was observed in the results and it is concluded that the test geometry is good for size effect studies in concrete. Furthermore, it was observed that with increasing strength the size effect becomes more pronounced as the brittleness is increased.