Fatigue, a process of gradual material deterioration under cyclic loading, poses a significant challenge in the design and safety of structures, particularly in the context of (quasi-)brittle materials. While various methods have been employed to analyze fatigue-induced failure, the phase-field approach stands out due to its ability to capture the complete fracture process from crack initiation to fatigue damage accumulation and final failure. Incorporating the micromechanics concepts provides insights into the underlying physical causes of fatigue phenomena. The micromechanics-based models [1] consider damaged materials as heterogeneous media composed of solid matrix weakened by isotropically distributed microcracks. They create a link between dissipation mechanisms like plasticity and damage at the macro level to the frictional sliding and opening of microcracks at the microscale. Therefore, this study focuses on the extension of the micromechanics-based phase-field model [2] to fatigue failure in (quasi-)brittle materials like concrete and mortar. To improve the model’s robustness and incorporate fatigue-related behaviors, plasticity evolution equations have been modified. The modification aims to enhance the algorithm’s stability for loading-unloading in the tensile regime, as discussed by Ulloa et al. [2]. Additionally, the fatigue degradation function [3] is integrated into the framework to account for the effects of cyclic loading on material deterioration. To validate the proposed methodology, a series of benchmark tests are simulated. The results demonstrate the model’s ability to accurately predict crack initiation, propagation patterns, and material response under varying cyclic loading conditions. REFERENCES [1] M. Sarem, N.E. Deresse, J. Ulloa, E. Verstrynge, and S. Fran¸cois, Micromechanics-based variational phase-field modeling of Brazilian splitting tests. Engineering Fracture Mechanics, 290:109472, 2023. [2] J. Ulloa, J. Wambacq, R. Alessi, E. Samaniego, G. Degrande, and S. Fran¸cois, A micromechanics-based variational phase-field model for fracture in geomaterials with brittle-tensile and compressive-ductile behavior, Journal of the Mechanics and Physics of Solids, 159:104684, 2022. [3] P. Carrara, M. Ambati, R. Alessi, and L. De Lorenzis, A framework to model the fatigue behavior of brittle materials based on a variational phase-field approach. Computer Methods in Applied Mechanics and Engineering, 361:112731, 2020.