Large-scale testing on specific fracture energy determination of dam concrete

The specific fracture energy of dam concrete is a basic material characteristic needed for the prediction of concrete dam behavior. Data on fracture properties of dam concrete are quite limited to date. A series of tests was carried out based on the size effect due to a number of geometrically similar notched specimens of various sizes. Experimental tests include three-point bending tests. The specimens were of square cross section with a span to depth ratio of 2/5. Three different specimens with depth of 200, 400 and 800 mm were considered for the purpose of testing. Concrete mixtures are provided from the Caroon 3 dam project site using river gravel or commonly crushed stones from quarries. To compare the fracture properties of dam concrete with normal concrete five types of concrete mixes of 65, 50, 40, 30 and 20 mm maximum aggregate size were considered. For all mixes, value of relative notch depth of 0.2 is used. Experimental results show that aggregate size has an important effect on specific fracture energy values of dam concrete. According to specific fracture energy definition based on size effect, the specific fracture energy of concrete mixes of 65, 50, 40, 30 and 20 mm M.S.A. are 178, 129, 88, 79 and 72 N/m, respectively. This indicates that the high specific fracture energy of dam concrete is the result of the nature, size and properties of its aggregate. The difference between specific fracture energy of normal and dam concrete should be noticed in nonlinear analysis of concrete dams.