Size effect on specific fracture energy of concrete

Abstract

Size effect on the specific fracture energy G F of concrete can be adequately modelled by an uneven fracture energy distribution along the crack path induced by the specimen boundary influence. The boundary influence on G F can be neglected only if a specimen is very large so that the boundary region is a very small portion of the total fracture area. The underlying principle on the specimen boundary induced size effect provides a simple and logical explanation for the commonly observed size effect on G F. The boundary effect model recently proposed by the authors is used in this paper to quantitatively evaluate the specimen boundary influence so that the size-independent fracture energy is derived, which otherwise can only be measured with very large concrete specimens. New experimental results from a very different material system, polymer, are analysed together with concrete results by the simple boundary effect model.