Effective crack model for the determination of fracture toughness ( [formula omitted]) of concrete

Abstract

A method is described for determining the fracture toughness of plain concrete from three-point bend specimens which accounts for the pre-peak crack growth that occurs upon loading. The fracture toughness so determined is shown not to depend on the size and geometry of the test specimen but on the mix variables only. The regression equations presented for determining the effective notch depth should be very accurate because they are based on an analysis of not only the authors' test data but that of several researchers around the world. They are shown not to depend on the size and geometry of test specimens. In fact, although these expressions were developed using three-point bend data, it is shown that they may be applicable to CT, CLWL, and four-point bend specimens. It is also shown that the predictions of the effective crack model are in good agreement with two non-linear models namely, the two parameter model and the size effect law.