Fatigue damage prediction of concrete using acoustic emission approach with account of concrete heterogeneity

Concrete, a ubiquitous construction material for structures like bridges, roads, and marine installations, is prone to fatigue damage caused by factors such as traffic loads, wind, and wave forces. Despite its wide usage, the intricate process of concrete fatigue failure remains relatively unexplored. Heterogeneity, a common attribute of materials, significantly influences how concrete behaves when subjected to fractures. This study aimed to address this knowledge gap by investigating how con- crete’s heterogeneity, particularly in terms of varying aggregate sizes, impacts its susceptibility to fatigue-induced fractures. The research employed beam specimens subjected to central loading under controlled loads. To continuously monitor the loading process, the study employed acoustic emission (AE) monitoring, a technique that captures acoustic events. The insights gleaned from the inves- tigation revealed noteworthy aspects of concrete behavior. The initial stiffness of concrete beams was found to be higher when larger aggregate sizes were incorporated. However, as the number of fatigue cycles increased, these beams experienced a gradual decline in stiffness. Notably, the rate of stiffness degradation escalated with higher cycle counts, and a pronounced drop in stiffness was observed right before beam failure, indicating a pivotal phase in concrete’s fatigue life. The AE technique emerged as a valuable tool for analyzing fatigue-induced damage in concrete. By monitor- ing AE events continuously, the study unveiled three distinct fatigue damage zones: crack initiation, gradual crack progression, and eventual beam failure. AE parameters effectively showcased the in- fluence of concrete heterogeneity, as represented by varying aggregate sizes, on its fatigue response. Notably, the AE event analysis consistently demonstrated a recognizable pattern of concrete failure under fatigue loading, affirming the reliability of the AE technique in tracing the fracture process. In summary, this research contributes insights into the intricate fatigue behavior of concrete, partic- ularly regarding how material heterogeneity, notably aggregate size variations, shapes this behavior. The findings underscore the significance of AE monitoring for comprehending fatigue and fracture characteristics, emphasizing the pivotal role of aggregate size in shaping these attributes. By enhanc- ing our understanding of concrete performance, this study aids in designing more durable and robust structures.