Softening of concrete must be considered as the stage where the material breaks down catastro- phically. For plain concrete and cement it can be shown that a macroscopic crack develops, most generally in asymmetric mode. This is caused by the…
Softening of concrete must be considered as the stage where the material breaks down catastro- phically. For plain concrete and cement it can be shown that a macroscopic crack develops, most generally in asymmetric mode. This is caused by the heterogeneous material structure of said materials. The macrocrack growth is affected by boundary conditions and specimen/structure size. The phenomena can be realistically described by means of a bridged crack model based on LEFM principles. Both for tension and compression the observed crack sequence from micro-cracking in the pre-peak regime to localized crack growth in the post-peak regime can be shown, with the exception that the macrocrack growth is in mode II in compression rather than in mode I. In both cases boundary effects are important and cannot be neglected. The paper shows that the unrestricted use of softening curves as material property is not allowed; rather every structure will have its own specific softening curve.