Effect of Reinforcement Corrosion on the Bond Strength of RC Members

Abstract

Corrosion of reinforcing steel is the most detrimental effect endangering the structural performance. Present investigation has been taken up to study the detrimental effect of corrosion on bond behaviour. Anchorage bond strength and Flexural bond strength characteristics are studied in this research. Two types of cements namely Ordinary Portland Cement (OPC) and Portland Pozzolona Cement (PPC) have been used. Bond strength study has been carried out for controlled beam specimen and for specimens subjected to different levels of corrosion. Loss in mass of reinforcement bar has been taken as the basis to fix corrosion levels. Accelerated corrosion technique has been adopted to control corrosion rate by regulating current over predetermined durations. For the study of anchorage bond strength, cylindrical specimens have been adopted. Concrete grade of M20 and Fe-415 grade of 16mm diameter bar have been used. From the study it has been observed that for corrosion levels upto 2.5%, bond strength is unaffected. But for corrosion levels beyond 2.5%, there is considerable decrease in bond strength. For understanding the performance of flexural bond strength, National Bureau of Standard (NBS) beams have been investigated. Concrete grade M30 and steel Fe-415 have been used. From the experimental investigation it has been observed that load carrying capacity drops by about 1.6%, for every percentage increase in corrosion level. Bond strength degradation of 2.6% at slip initiation and 2.1% at end of slip have been observed for every percentage increase in corrosion level for OPC concrete beam specimens. For PPC concrete, bond strength degradation of 2% at slip initiation and 2.1% at end of slip have been observed. In numerical study, finite element method was used. ANSYS commercial software is used for the study. From the numerical modelling it has been observed that load carrying capacity drops by about 1.8%, for every percentage increase in corrosionlevel. The bond strength degradation values are 3% and 2.4% at initiation of slip and end of slip respectively per percentage increase in corrosion level. Lastly, an attempt has been made to apply the proposed prediction equations to estimate corrosion in real life structures.