INFLUENCE OF AGGREGATE SIZE ON FRACTURE PROCESS ZONE OF CONCRETE DETECTED WITH 3-DIMENSIONAL ACOUSTIC-EMISSION TECHNIQUE

Three dimensional acoustic emission technique is applied to observe the phase of the fracture process zone of concrete which is created ahead of the crack tip and significantly influences the tension softening behaviour of concrete. The results show that the fracture process zone is already created at the peak load and then the active AE event zone moves towards the bottom of the specimen. It is also revealed that the fracture process zone may expand as the crack grows and the expanding rate of the process zone is influenced by the aggregate size.