Asymptotic analysis of boundary-effect on strength of concrete

A new size effect model is presented, which deals with the specimen boundary influence on the strength of concrete measured from the maximum load tests. The new boundary effect model shows that the size independent tensile strength and fracture toughness (and then the specific fracture energy) of concrete-like quasi-brittle composites can be conveniently determined from the simple maximum load tests. The common size effect observed using geometrically similar specimens is only a special case of the specimen boundary effect on fracture properties of concrete. The difference and similarity between the current boundary effect model and the common size effect models are discussed and illustrated with concrete results measured from four different sets of geometrically similar specimens. It is shown that the asymptotic analysis of the large plate with a small edge crack, for which the front specimen boundary rather than the specimen size needs to be considered, provides the solution to all the quasi- brittle fracture transition curves, or the size effect.