Determination of residual fracture parameters of post-fire normal strength concrete Up to 600 °C using an energy approach

According to the double-G fracture model (G means energy release rate), the residual fracture behavior of post-fire normal strength concrete is described. The initial fracture energy release rate and the unstable fracture energy release rate are termed to distinguish the different crack propagation stages. The difference between the two energy release rates, named as the cohesive energy release rate, is to be induced by taking into account the aggregate bridging interlock. In total ten temperatures and fifty specimens are considered. The double-G fracture parameters are then experimentally determined. Based on the assumed relationship among the three energy release rates, the calculated unstable fracture energy release rate is obtained. Finally the feasibility of the double-G fracture model is verified.