Effect of corrosion products on bond strength and flexural behaviour of reinforced concrete slabs

Abstract

New performance-based design codes are currently being developed, where the design life of reinforced concrete structures will be estimated by taking into account not only the time to initiation of reinforcement corrosion, but also the time it would take for the extent of corrosion to reach a level where the structure is no longer fit for purpose. It is therefore important to establish what level of corrosion, if any, can be permitted before the structural behaviour of the reinforced concrete member is affected. In this paper the effect of corrosion products on the bond strength and flexural behaviour of reinforced concrete slabs was investigated. Pull-out tests confirmed that low levels of corrosion (less than 2% loss in steel cross-sectional area) can result in improved bond between the reinforcing bars and the concrete. At higher corrosion levels the empirical bond decay functions proposed by various researchers accurately predict the bond strength. The flexural behaviour of the slabs is affected by the reduced bond between the steel and the concrete, and this manifests during the load tests in a reduction in the number of cracks but an increase in crack width, with increased corrosion levels. At high corrosion levels (more than 8% loss in steel cross-sectional area) the flexural behaviour of the slabs is affected to such an extent that brittle failure occurs.