STUDY ON LOCAL FRACTURE ENERGY DISTRIBUTION IN MORTAR SPECIMENS

Size effect on fracture energy of cementitious materials can be explained reasonably in virtue of the local fracture energy distribution along the ligament of specimen. The correlation between the peak load and the local fracture energy at the crack tip region is established analytically for three-point-bending notched beams of mortar. Then tests are carried out for beams with different depths and different notch-to-depth ratios. Upon the comparison between the analytically predicted peak loads and the experimentally measured loads, the values of local fracture energy at different crack tip regions are determined, and then the local fracture energy distribution along the ligament of the specimen can be obtained. Results show that the local fracture energy distribution of mortar is affected by the front and back free boundary effects and the fictitious boundary effect at the notch tip, which is very similar with the phenomenon observed in concrete. A Tri-linear model of the local fracture energy distribution is yielded with almost constant values far away from the back free boundary and the fictious boundary, but decreased values towards the referred two boundaries. Therefore, it can be concluded that the tri-linear model is suitable not only for concrete, but also for mortar and other cementitious materials.