Effect of Aggregate and Specimen Size on Fracture Properties of Dam Concrete

Abstract
Fracture properties of concrete used in dams are obtained from laboratory experiments of large wedge‐splitting specimens with heights of 31 cm (12 in.), 91 cm (36 in.), and 152 cm (60 in.). Various concrete mixes of 19 mm (0.75 in.), 38 mm (1.5 in.) and 76 mm (3.0 in.) maximum size aggregate were investigated. The fracture toughness, Kic, and specific fracture energy, GF, are found to be aggregate and specimen‐size independent, only if certain minimum specimen dimensions are exceeded. However, they appear to be dependent on the aggregate shape and type. For the two types of aggregates used in this experimental program, more energy was required to fracture the subangular aggregates than to debohd the rounded ones. Finally, a set of laboratory specimens were used to evaluate the fracture properties of cold joints between lifts found in concrete dams. The fracture properties for cold‐joint wedge‐splitting specimens exhibited larger scatter in test results, and were lower than for specimens without cold‐joints.

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