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

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.

Bond Behavior of Reinforced Concrete Considering Freeze–Thaw Cycles and Corrosion of Stirrups

“…Furthermore, the reduction of the stirrup spacing can increase the bond strength and ultimate slip [15]. This is mainly due to the fact that when the stirrup spacing is small, the densification of the stirrups inhibits the cracking of the concrete and the reduction of the bond strength between the reinforcement and the concrete [31].…”

Modelling Strategies for the Numerical Simulation of the Behaviour of Corroded RC Columns under Cyclic Loads

“…Several experimental studies and analytical formulations are available in the literature for the evaluation of the bond between concrete and corroded bars [4,[37][38][39]. In this paper, the law proposed by [40], based on regression analyses of experimental data is adopted for the bond degradation as a function of the corrosion penetration. The model accounts for the amount of transverse reinforcement and predicts the residual bond strength, in relationship to either corrosion penetration or surface crack width.…”

Corrosion Effects on Durability of RC Structures

“…Five research papers have been published in Special Issue of Metals titled Corrosion Effects on the Durability of RC Structures. The collected articles deal with several aspects of the corrosion phenomenon in reinforced concrete, including the copper corrosion behavior in simulated concrete-pore solutions [1], the influence of microstructure on the corrosion resistance of steel bars and their fatigue behavior [2], the degradation of bond mechanism between steel and concrete [3,4], and the flexural capacity of corroded Prestressed Reinforced Concrete (PRC) beams [5].…”

“…The experimental outcomes indicate that the densification of stirrups limits concrete-cracking development through confinement, leading to higher bond strength values and delaying the degradation of bond loss as corrosion damage increases [3]. Given that the recommendations of Model Code 2010 refer to the presence or absence of stirrups (links) as an on-off criterion, the abovementioned experimental data were compared with the Model Code recommendations, combined with other available data from the literature [4]. A discretization of confinement levels is proposed, according to experimental data, to represent different cases of stirrups density often occurring in real RC elements, and predictive zones of residual bond strength in relation to either corrosion penetration or surface crack width were extracted.…”