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Giao Vu, Jithender J. Timothy, Tagir Iskhakov, Günther Meschke

• Concrete is a quasi-brittle material with a heterogeneous morphology across multiple scales, which also influences the evolution of damage in case of loading. Damage in concrete structures is initiated by growth of diffuse microcracks that is followed by damage localization eventually leading to structural failure. Thus, diffuse microcracking processes can be considered as failure precursors. Identification and characterization of these precursors can be applied in conjunction with structural health monitoring based on diffuse ultrasonic waves to develop early warning systems against catastrophic failure of concrete structures. To this end, a multiscale model for a simulation-based description of diffuse damage in concrete is proposed. At the scale of the cement paste, microcrack growth is modeled by a combination of continuum micromechanics and linear elastic fracture mechanics [1]. The micromechanics model is incorporated into a reduced-order Lippmann-Schwinger based meso-model for concrete [2], [3]. The mesoscale model is generated using Random Sequential Adsorption of realistic aggregates based on concave slicing of randomly cut polyhedrons. The influence of the microcrack morphology at the microscale on the diffuse microcracking and overall concrete stiffness degradation is presented.