Experimental study on bending fatigue properties of microcapsule self-healing cementitious composites

The service life of concrete structures is significantly reduced under cyclic loading; however, the mechanical properties under the combined effects of cyclic loading and microcapsules containing healing agents remain unclear. This study investigates the influence of microcapsules on the fatigue behavior of cement mortar, encompassing fatigue life, cyclic crack mouth opening displacement (CMOD), dynamic stiffness, maximum crack mouth opening displacement, and fatigue damage. A static three-point bending test was conducted to determine the static peak load. The three-point bending fatigue test was then performed at stress levels of 0.7, 0.8, and 0.9, relative to the static peak load. The Weibull probability distribution and Who<spacing diaeresis>ler fatigue equation were deployed to scrutinize fatigue failure, establishing the relationship between stress level, fatigue life, and fatigue failure probability. The microstructure of the fracture surface was examined through scanning electron microscopy (SEM). The results indicate that compared to cement mortar without microcapsules, specimens containing 6 % microcapsules demonstrate an average fatigue life enhancement of 1.4 times at a stress level of 0.8, and 1656 times at a stress level of 0.9. The incorporation of microcapsules hinders the unstable propagation of cracks, slows down the decline in stiffness, and enhances the maximum deformation of cement mortar during the fatigue damage process. On a microscopic scale, the presence of microcapsules leads to an increase in the number of pores; conversely, the ruptured microcapsules exhibit an inhibitory effect on microcracks.