Effect of chloride-induced corrosion on bond performance of various steel fibers in cracked SFRC

This study investigates the chloride-induced corrosion behavior of various steel fibers and associated effects on their interfacial bond performance in cracked steel fiber reinforced concrete (SFRC). Three types of deformed fibers, including hooked-end (H), crimped (C), and milled-cut (M) fibers, were embedded in high strength matrix and then exposed to wet-dry cycles of chlorides under cracking conditions. The scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) technique were employed to gain insights into the surface morphologies and corrosion products at the micro-scale. The bond behaviors of corroded fibers were further evaluated through pull-out tests, where the influences of fiber type, corrosion duration, crack width, and embedded length were discussed. Three distinct corrosion morphologies were identified on the surfaces of three types of fibers owing to the difference in corrosion products. After 40 days of corrosion, the average bond strength of H fibers increased by 37.9% because of dense and rough rust layer, while those of C and M fibers deteriorated by 30.5% and 18.8% due to surficial groove loss and loose rust layer. The average bond strength of H, C, and M fibers improved by 12.4%, 11.7%, and 58.0% as the crack width increased from 0.1 to 0.3 mm, whereas significant reductions in pull-out energy and equivalent bond strength were obtained once the crack width exceeded 0.2 mm owing to fiber fracture. The corrosion-induced bond deterioration of M fibers became less severe as the embedded length increased up to 12 mm and remained unaffected thereafter.