Investigation of chloride ion diffusion mechanism and durability analysis of offshore concrete structures under fatigue loading

This study examines the diffusion behavior of chloride ions in damaged concrete under fatigue loading, focusing on the influence of fatigue cycles and stress levels on chloride ion diffusion. Cyclic loading and NaCl solution immersion tests were performed at various stress levels to measure chloride ion concentrations at different depths within the damaged concrete. Based on experimental data, a two-dimensional chloride ion diffusion model was developed and validated using numerical simulations to evaluate the influence of crack width and depth on the diffusion coefficient. The results indicate that fatigue-induced cracks significantly enhance chloride ion penetration, with the diffusion coefficient increasing by up to 2.45 times under high stress levels (f/f_u = 0.6). CT scans showed that wider and deeper cracks facilitated chloride ion transport by expanding the crack-affected zone and transitioning the diffusion mechanism from one-dimensional to two-dimensional transport. The validated two-dimensional diffusion model offers potential for accurately predicting chloride ion ingress in offshore concrete structures. These findings contribute to improving the durability assessment and maintenance strategies for marine infrastructure.