Transition from energy dissipation to crack openings during continuum–discontinuum fracture of concrete

Fracture in quasi-brittle materials like concrete is mainly governed by two processes: energy dissipation and discontinuous displacement fields or discrete cracks. In this study we discuss the simultaneous development of both types of fracture. Energy dissipation and crack openings are analyzed during the fracture development by acoustic emission and digital image correlation (DIC) respectively. DIC results are processed using nonlinear damage modelling and lattice element modelling to reveal the microcracking zone. It is observed that overall failure mechanism is governed by three processes (1) high energy dissipation phase during which energy release rate increases (2) continuum–discontinuum transitional phase where energy dissipation rate attains its maximum value, and (3) discontinuum phase where energy dissipation rate drops and crack openings start increasing.