Size effect: Influence of proximity of fracture process zone to specimen boundary

Size effect on strength of cementitious materials was studied successfully many years ago by a crack-bridging model through detailing the influence of the resistance R-curve behaviour on quasi-brittle fracture. The condition that specimens of different sizes have to be geometrically similar, commonly assumed for size effect study, was proven unnecessary. The present study emphasizing the interaction between the fracture process zone and structure boundary agrees with the crack-bridging analysis, and further points out that physical size itself is not the key mechanism for the apparent size effect.