A comparison of precursor and failure mechanism of rubber and ordinary mortar with compound fissures

Rubber mortar is widely used due to its excellent crack resistance and thermal insulation properties. However, its failure precursors, especially crack tip strain localization, crack initiation and propagation process were scarcely investigated. This study employed uniaxial compressive test (UCT) and Particle Flow Code (PFC 2D ) simulation to compare strain localization and crack behavior in ordinary and rubber mortar considering the interaction of compound fissures. Results indicate that prefabricated cracks significantly reduced the more strength of ordinary mortar(42%) than rubber mortar(24%). Subsequently, the stress-strain curve of rubber mortar exhibited significant fluctuations, which revealed considerable energy dissipation(50.0 J.m -2 ) of interface frictional and enhanced deformation resistance post-failure. Furthermore, strain localization based on Gini coefficient(from 0.038 to 0.084) and von Mises strain(from 0.07 to 0.16) was modified with rubber and fissure distribution. The initial cracking stress of ordinary mortar was relatively high and quickly formed. These findings, from a mesoscale perspective, demonstrated the superior crack resistance of rubber mortar. Additionally, fracture morphology and microstructures were examined using Scanning Electron Microscopy (SEM) and PFC 2D simulations. the SEM tests revealed a high roughness coefficient on fracture surfaces and small pores of rubber mortar with cross fissures, while PFC 2D simulations unveiled a high stress intensity coefficient around large pores in ordinary mortar. These conclusions can serve as valuable references for concrete design and construction. • Strain localization was characterized with Gini coefficient and Von Mises strain; • (2)Crack morphology and failure mechanism were analyzed according to SEM and DIC images; • (3)The precursors of mortar were found from shear-tensile to ductile failures with the addition of rubber.