Evaluation of residual flexural behavior of corroded fiber-reinforced super workable concrete beams

This study investigates the effect of macro synthetic fiber (MSF) volume and crack widths on corrosion of the reinforcing bars and residual flexural behavior of fiber-reinforced super-workable concrete (FR-SWC) beams exposed to accelerated corrosion. FR-SWC beams prepared with 0, 0.33%, and 0.66% MSF were pre-cracked at 0.2-, 0.4-, and 0.75-mm widths before corrosion testing. The controlled crack width was initiated in one set of beams that were then unloaded. The crack width was maintained for another set of beams during corrosion testing by inserting a shim. Test results showed that the use of 0.33% and 0.66% MSF reduced crack development and crack propagation, delayed corrosion initiation time, and significantly increased the residual flexural strength of beams subjected to accelerated corrosion. The beams reinforced with 0.66% MSF enhanced residual ultimate load, residual yield load, and residual flexural toughness by 10%-45%, 38%-113%, and 42%-150% compared to the corresponding non-fibrous beams. The improved flexural performance of beams made with MSF after accelerated corrosion can be attributed to the ability of MSF to reduce crack width due to corrosion damage. Crack width lower than 0.2 mm showed no significant effect on the residual flexural behavior of beams after corrosion testing. However, the pre-crack width over 0.2 mm showed a significant influence on the crack initiation and residual flexural behavior after accelerating corrosion. The pre-cracked beams with a 0.75 mm crack width retained the ultimate load of 65%-76%, yield load of 47%-80%, and toughness of 38%-83%, respectively, compared to their corresponding uncracked beams subjecting to accelerated corrosion. The un-shimmed beams allowed partial closure of cracks due to the presence of MSF after initial loading and increased the residual ultimate load, yield load, and flexural toughness by 7%-45%, 27%-82%, and 3%-56%, respectively, compared to their corresponding shimmed beams. A correlation between the residual flexural behavior and the rate of cross-sectional area loss of reinforcing bars due to corrosion was developed. Further-more, a mechanism was proposed to explain the effect of MSF in improving the residual flexural performance in the cracked FR-SWC beams.