FRACTURE PROCESS ZONE IN CEMENTITIOUS MATERIALS

The current work is directed to the measurement and prediction of the fracture process zone (FPZ) with the compliance method. The method is renovated with a multi-cutting technique. A new compliance curve C(p) is established while FPZ in a damaged specimen is removed stepwise by saw-cutting. The length of FPZ can be well determined from C(p) in comparison with the compliance calibration curve. Results of two different mortars evidence that the multi-cutting method is applicable to cementitious materials. A general theory is presented in conjunction with the multi-cutting experiment. The bridging stress transferred within FPZ is evaluated from C(p) by the theory. It is proven with a numerical simulation that the strain-softening relation derived from C(p) predicts well the global load and displacement relationship. The extension of FPZ at various stages of fracture can also be predicted with the theory if parameters of the strain-softening are available. Both experimental and analytical results affirm the intrinsic connection among FPZ, fracture toughness and fracture energy.