A new way to analyse the size effect in quasi-brittle materials by scaling the heterogeneity size

Abstract

Size effect has been a major problem in the design of quasi-brittle materials like concrete. The existing approaches consider the determination of size independent properties mainly by testing geometrically similar specimens. These specimens vary in size from small to large. Often it is difficult to perform testing on these specimens because of their size. Moreover, these approaches do not consider the role of microstructure or the heterogeneity size, which is the source of size effect. In this paper, a new size effect model is presented, which takes into account the heterogeneity size (aggregate size for concrete). Several series of tests are performed on concrete where an original approach to investigate size effect is applied by scaling the heterogeneity size instead of scaling the specimen size. The proposed size effect model makes it possible to determine the size independent fracture properties. The role of the ratio of the structural size to the heterogeneity size is clearly established in the size effect approach. The size effect curve and the fracture parameters obtained by using new size effect model perfectly match with those of Bažant’s size effect; however, the former is much easier to perform experimentally or numerically.