Fracture energy estimation in mortar: a dual-method approach integrating three-point bending experiments and numerical simulation

Understanding the fracture energy of building materials is important for predicting long-term performance and safety of civil structures. As a key component of masonry, mortar is exposed to diverse environmental and loading conditions that can lead to crack nucleation and propagation. Accurate estimation of its fracture energy enhances construction practices and optimises maintenance strategies. While currents methods to measure fracture energy are well established, challenges remain in standardising techniques and addressing variability in specimen sizes and materials heterogeneity. Here, we evaluate the fracture energy of mortar using both a novel numerical simulation approach and three-point bending tests (3-PBTs) using semicircular notched specimens. The simulation calculates the energy dissipated along the crack path by experimentally calibrating the relative crack mouth opening compliance (λCMOD) with respect to the elastic compliance (λ0, CMOD). The size effect law is applied to provide deeper insights across different scales. The results indicate that fracture energy increases with CMOD consistently across both methods, validating the proposed numerical approach. This research underscores the importance of estimating fracture energy during cracks initiation and propagation under bending loads, demonstrating consistency with established nonlinear fracture mechanics frameworks for quasi-brittle materials, and suggests further investigation into specimen size effects by using larger specimens.