Detecting and Evaluating Fatigue Damage Mechanisms in Concrete with Embedded Aggregate Sensors

Fatigue damage is a critical factor for the long-term service performance degradation of concrete structures. Nevertheless, the mesoscopic fatigue process is still debatable due to material heterogeneity and the complex internal damage progression. To further investigate the internal damage mechanism of concrete under fatigue loading, this study quantitatively monitors the dynamic internal strain evolution of concrete prismatic specimens during uniaxial compression high-cycle fatigue by designing and embedding aggregate sensors (EAS). The results indicated that EAS may effectively reflect concrete cracking, and the approach can properly capture the internal strain field redistribution features of concrete. Significant internal strain localization was observed during fatigue damage. The turning points in strain evolution, which correlate with the stages of stable propagation and microcrack initiation, were identified. Furthermore, the evolution of internal strain effectively characterized the alteration of stress transfer routes induced by crack propagation. Based on failure modes and mechanical analysis, the synergistic driving mechanism of fatigue damage involving crack growth, interfacial friction and stress field evolution was investigated. The difference in concrete damage under fatigue and monotonic loading due to changing mesoscopic crack propagation was defined, establishing a mechanical foundation for exploring concrete fatigue damage processes. The EAS monitoring method used in this study not only gives a viable approach for the fatigue damage analysis of concrete structures, but it also offers a new viewpoint and data support for comprehending the mesoscopic fatigue mechanism of concrete.