Nondestructive assessment of corrosion of reinforcing bars through surface concrete cracks

Abstract

Degradation of reinforced concrete (RC) structures is a serious safety problem affecting all industrialized countries, and economical aspect of this problem cannot be neglected. One of the main reasons for the degradation of RC is the corrosion of steel reinforcing bars as a result of concrete cover cracking and bar cross section reduction. As a consequence, the structural capacity of reinforced concrete elements decreases progressively as degradation develops. The use of nondestructive testing (NDT) and/or analytical formulation can represent high-quality and rapid methods to evaluate the corrosion penetration of bars, and provide a useful parameter to design a retrofit. This paper presents an additional tool that can be used to evaluate and assess the vulnerability of existing structures in terms of determination of bar cross section lost. This can be accomplished by calculating reinforcing bar cross section loss due to corrosion by measuring external crack widths of the concrete cover by using simple charts and formulas. Predictions were obtained by using two analytical models, developed by the authors. Their predictions have been satisfactorily compared to both the literature and novel experimental results, and compared to previous empirical models available in scientific literature. The experimental results were obtained by corroding real scale concrete specimens reinforced by using smooth and ribbed bars (according to old and modern building codes) using 3.5%wt sodium chloride solution and an imposed current.