Effect of coarse aggregate volume fraction on mode II fracture toughness of concrete

Abstract

Mesostructure, cement, and interfacial transition zone (ITZ) play a vital role in the fracture process of concrete. This paper focuses on the effect of coarse aggregate volume fraction on the mode II fracture behaviors of concrete by the laboratory experiments. The tests of sixty concrete specimens were performed under different volume fractions of coarse aggregate of 19%, 25%, 31%, 37%, 43%, and 50%. The mode II fracture toughness and energy release rate were determined by the compression on half part of the non-notched specimens. The experimental results show that the mode II fracture toughness KIIC and the critical energy release rate GIIC increase with increasing the volume fraction of coarse aggregate from 19% to 37%, and then both decrease with increasing the volume fraction of coarse aggregate from 37% to 50%. The technique of digital image correlation (DIC) was also used to track the fracture evolution during the tests and it was found that the shape of fracture process zone (FPZ) of concrete with mode II fracture is a curved band around the potential shear ligament.