Effect of hybrid fiber reinforcement on corrosion-induced damage of reinforced concrete

Abstract

The corrosion of steel reinforcing bars in concrete structures is a primary durability concern in aging infrastructure. Cracks caused by the internal growth of corrosion products increase the permeability of the matrix and degrade the designed capacity of structural elements. In this longterm study, two types of hybrid fiber-reinforced concrete (HyFRC) – a baseline HyFRC and a selfconsolidating HyFRC (SC-HyFRC) – are investigated for serviceability enhancement under a twostage corrosion model (time to corrosion initiation and damage during corrosion propagation). HyFRC, which contains a synergistic blend of microfibers and macrofibers, utilizes a multi-scale approach towards crack control and is extended to durability-related applications. Reinforced HyFRC and reinforced concrete beams were exposed to chloride penetration and monitored for corrosion activity for up to two years. Because concrete structures are subjected to various crack-inducing loads while in service, beam specimens in this study were placed under a cyclic, flexural preloading protocol prior to induced corrosion to account for such service conditions. The time to corrosion initiation was found to increase with reduced maximum flexural crack widths and suppression of surface splitting cracks during preloading, both of which were improved by HyFRC compared to concrete. Crack resistance provided by hybrid fiber reinforcement was evident during the corrosion propagation stage, as additional surface cracking was not detected with reinforced HyFRC and residual flexural testing revealed no significant degradation in flexural performance. In contrast, damage to reinforced concrete beams resulted in nearly complete loss of rebar-matrix bond due to extensive splitting crack formation and widening. The results suggest hybrid fiber reinforcement was effective in resisting tensile stresses from mechanical loading and from the internal growth of corrosion products, ultimately limiting the damage to reinforcing steel and maintaining the service capacity of beam elements.