Chloride concentration distributions in fatigue damaged RC beams revealed by energy-dispersive X-ray spectroscopy

In this laboratory study, the chloride concentrations at the steel-concrete interfaces of fatigue damaged RC beams were investigated by energy-dispersive X-ray spectroscopy. The beam specimens were subjected to fatigue loadings followed by 3.5 wt% NaCl solution wet-dry cycles. For the two bars in one beam, the fatigue-fractured steel exhibited severe corrosion (30%–40% corrosion area) and high chloride concentrations (0.5 wt%–0.9 wt%) in the pure flexural segment. When the load level (ratio of maximum fatigue load to ultimate static strength) reached 0.45 or after 1.2 million cycles of fatigue loading, the fatigue damage affected the chloride concentrations of compressive concrete. The increase of load level from 0.4 to 0.45 caused at least 30% increase in the chloride concentrations of tensile concrete and 6.24 times decrease in the residual fatigue life, but the initial fatigue loading cycles barely affected either of them. Results of the chloride concentrations were consistent with those of the residual fatigue life test.