Size effect and fracture energy studies using compact compression specimens

Abstract

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 crosssectional area (length = depth) and constant thickness (100 ram) were used in the experimental work; the length/depth dimensions of the test specimens were 100, 150, 200, 300, and 400 ram, 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 ram. 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. RI~SU MI~

Usage of compact compression specimens to determine non‐linear fracture parameters of concrete

“…The test presented in type I was commonly used to evaluate the fracture properties based on LEFM whereas type II was utilized to evaluate the fracture energy of concrete with medium and high strength values. 18 In previous studies on CCS, the values of K I were only determined because CCS was only used for LEFM-based analyses of concrete. It is also well-known that at least two fracture parameters that were determined experimentally are necessary to achieve modelling of a concrete structure by adopting principles of fracture mechanics.…”

“…compression specimens (CCS) were utilized in the determination of fracture parameters, which covered fracture toughness or critical strain energy release rate or fracture energy in cementitious material according to the fracture mechanics of Hookean materials. [12][13][14][15][16][17][18] As mentioned above, the proper simulation of a concrete structure, as well as the fracture toughness parameter, requires at least one more parameter in length dimension.…”

“…Additionally, the FEM was also employed in the derivations of stress intensity factor in specimens with notches that were under wedge loads. To investigate the coherence of fracture behaviour of CCS with the model that was created by utilizing the concrete fracture models above, 11 series of experimental studies on CCS [12][13][14][15][16][17][18] were simulated. Additionally, two prediction formulae based on previous test data were proposed to estimate unstable fracture toughness and initiation fracture toughness of concrete.…”

Double cantilever indirect tension testing for fracture of quasibrittle materials

“…Furthermore, the size effect curve yields information on the brittleness of the specimens but the work of fracture method does not. In the case of concretes, the size effect method was applied successfully to the failure of concrete structures failing in tension, in diagonal shear, in torsion [27,28], in pull-out of reinforcing bars [29], in bond splice [30], in compression [31,32,33,34], in bending [35,36,37] as well as by Arcan tests [38].…”

Size Effect in Compression of High Strength Fibre Reinforced Concrete Cylinders Subjected to Concentric and Eccentric Loads

“…For this reason the description of the behavior of concrete is incorrect in terms of plasticity, and thus a size effect is observed. Recent developments in fracture mechanics have shown that the size effects which are observed in the failure of concrete structures are due to the concrete rather than the steel; this is true not only when the concrete fails in tension, (diagonal shear, bar pull-out, torsion, etc), but also when the concrete fails in compression, except when there are confining pressures that greatly exceed the uniaxial compression strength [2][3][4] . Recent studies [5][6][7] have shown that by adding sufficient quantities of randomly distributed short fibers of appropriate geometries to the matricesit is possible to improve the behavior of plain concrete and conventionally reinforced concrete in terms of both ductility and residual strength, especially in the case of high strength concrete.…”