Using SCB specimens to quantify nonlinear fracture characteristics in concrete and rock materials

Abstract

The normalized stress intensity factors for semi-circular bending (SCB) specimens have only been derived up to now. Therefore, experimental investigations on SCB specimens have been limited in terms of concrete fracture. In this study, the important linear elastic fracture mechanics formulas for SCB specimens are initially derived using the finite element method to evaluate the stable and unstable crack growth states of cracked quasi-brittle structures. Cement-based SCB specimens and beams are produced in two sets (concrete and mortar) and subjected to bending tests. The test results of the aforesaid specimens are compared according to three popular fracture approaches in concrete fracture: the two-parameter model, the size effect model, and the double-K model. It is concluded that there is a strong correlation between the fracture toughness of beams and SCB specimens for each set. Based on this agreement, three series of SCB rock experiments in the literature are subsequently examined using the aforesaid concrete fracture models. The results of this investigation illustrate that nonlinear fracture characteristics of rock and concrete materials can easily be estimated by employing single-sized SCB specimens.