Correlation between Cohesive Crack-Tip Local Fracture Energy and Peak Load in Mortar Beams

Abstract

Mortar, as concrete-like coarse-structured materials, has a fracture process zone ahead of crack tip after the crack initiation. The maximum fracture load must be related to the cohesive crack-tip local fracture energy due to the relatively limited crack growth in the critical state. The intention of this paper is to correlate the local fracture energy with the maximum loads in mortar specimens. An analytical approach is proposed on the correlation between the two parameters. Then a fracture test has been performed on three-point-bending notched mortar beams with a wide range of notch depths. Upon comparison of the predicted and experimentally measured peak loads, it is found that the crack-tip local fracture energy indeed varies with notch depth and beam height. Thus, the trilinear model for the local fracture energy distribution is confirmed in mortar specimens, indicating both the front and back free boundary effects. Based on the trilinear model, the size-independent fracture energy can be obtained if the notch depth and the ligament length are long enough. The proposed approach is analytical and convenient without the load-displacement curves in tests.