Correlation between characteristics of fracture process zone and tension-softening properties of concrete

The microcracking properties of concrete are studied by means of the three-dimensional acoustic emission technique in order to discusse the phases of the fracture process zone of concrete. It is revealed that the length of the fracture process zone ahead of the notch tip: seems to be independent of the maximum aggregate size but the width is obviously influenced by this factor. The tension-softening properties are analysed as an inverse problem. Among the four parametes defining a bilinear tension-softening diagram, the critical crack width is most influenced by the heterogeneity. The numerical results are correlated with the phases of the fracture process zone. The size dependence of the fracture energy of concrete is also discussed on the basis of the characteristics of the fracture process zone and an empirical formula is proposed to describe the size dependence.