Bilinear tension softening diagrams of concrete mixes corresponding to their size-independent specific fracture energy

•A procedure for constructing bilinear tension softening diagrams of concrete mixes.•The tension softening diagram corresponds to the size-independent fracture energy of the mix.•Inverse identification based on hinge model. The study of the fracture behaviour of concrete structures using the fictitious crack model requires two fracture properties of the concrete mix, namely, the size-independent specific fracture energy GF, and the corresponding tension softening relation σ(w) between the residual stress carrying capacity σ and the crack opening w in the fracture process zone ahead of a real crack. In this paper, bi-linear tension softening diagrams of three different concrete mixes, ranging in compressive strength from 57 to 122MPa whose size-independent specific fracture energy has been previously determined, have been constructed in an inverse manner based on the concept of a non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams.