Study of the Residual Bond Strength between Corroded Steel Bars and Concrete—A Comparison with the Recommendations of Fib Model Code 2010

Konstantinos Koulouris,Charis Apostolopoulos

doi:10.3390/met11050757

Abstract

As is well known, corrosion of steel reinforcement deteriorates the steel–concrete interface and causes concrete cracking, degrading significantly the bond strength. Several experimental studies have investigated the magnitude of residual bond strength due to corrosion, which affects either the function of corrosion-damaged steel bars or the surface crack width in concrete. As a result, linear and exponential correlation relationships have been proposed in order to predict the bond loss due to corrosion. Based on the results of an ongoing experimental campaign on the degradation of bond strength of RC specimens, combined with comparable outcomes from existing literature, this manuscript summarizes a database, comparing with the recommendations of Model Code 2010, to analyze and interpret the corrosion effect on the bond loss and highlights some points that need improvement in the current regulations. As indicated, the density of transverse reinforcement (stirrups spacing) has intense impact on the resulting bond loss due to corrosion. Hence, in order to quantify this aspect, the present manuscript introduces a discretization of confinement levels of RC elements, depending on the stirrups spacing. Based on this, regression analyses of data were conducted to extract fitting curves of bond loss, taking into account the amount of transverse reinforcement and predictive zones of residual bond strength in relationship to either corrosion penetration or surface crack width. Furthermore, the outcomes demonstrate that the corrosion penetration depth is an appropriate assessment tool to correlate the residual bond strength with the corrosion level, whereas the surface crack width on concrete is not yet an effective index, since there is a plethora of factors affecting the crack width. Due to this, more research is needed to improve the current level of knowledge on the surface crack width and link it with the corrosion damage of the steel bar and the residual bond strength due to corrosion.

Highlights

Reinforced concrete (RC) is the most widely used construction material of existing building stock, providing high bearing capacity and ductility, compared to its low production costs
In order to compare the collected database with the recommendations of Model Code 2010 [37], bond loss values are presented in Figure 7, as a function of Metals 2021, 11, x FOR PEER REVIEWcorrosion penetration
The collected values of percentage mass loss of steel bars were expressed in terms of corrosion penetration, using Equation (5) [25]: After the completion of the experimental values of corrosion level, average crack width of surface terms of percentage mass loss of the reinforcing concrete cracking and normalized bond strength were extracted

Summary

Introduction

Reinforced concrete (RC) is the most widely used construction material of existing building stock, providing high bearing capacity and ductility, compared to its low production costs. The durability of RC structures is adversely affected by the corrosion of steel reinforcement, since it degrades the mechanical performance of both the steel bars and concrete and, mainly, the bond mechanism between them, which plays a key role in ensuring their proper interaction. A report conducted by the National Association of Corrosion Engineers (NACE) [2] indicates that the cost of corrosion is estimated globally to be USD 2.5 trillion, or approximately. 3.4 percent of the global gross domestic product (GDP). [2] indicates that the cost of corrosion is estimated globally to be USD 2.5 trillion proximately 3.4 percent of the global gross domestic product (GDP).

Methods

Results

Conclusion