Abstract
Although corrosion of reinforcement is a well-known issue for the construction industry, there are still open questions about some fundamentals of corrosion in reinforced concrete. These points include, among others, which are the most sensitive locations of the steel/concrete interface for pitting corrosion to initiate and to propagate. In this study, X-ray computed tomography (CT-scan) is used to characterize eight 20-years-old reinforced concrete cores naturally deteriorated due to chloride-induced corrosion. The volume loss due to corrosion of the reinforcement was quantified through image analysis of CT-scans. The volume loss of the steel was found to be higher for steel rebars embedded in Portland cement specimens rather than in blended cement specimens. Furthermore, CT-scans revealed that the deepest and most frequent corrosion pits, as well as the consequent highest volume loss of steel, were present at the portion of the reinforcement closer to the outdoor environment and in proximity to air voids at the steel/concrete interface. As a consequence, the highest decrease of structural performance of the rebars would be likely localized at those locations. Therefore, the presence of interfacial air voids should be considered as relevant factor when assessing the risk of corrosion of reinforced concrete structures.
Highlights
Chloride-induced corrosion of steel reinforcement is a common cause of deterioration for reinforced concrete structures [1]
The highest average volume loss for blended cement specimens was measured for V/A-1
Cracks probably allowed for more aggressive ingress of electrolyte and harmful agents, resulting in higher average volume loss than rebars embedded in blended cement-based concrete and especially than V/A-2, which was cast with identical cement type (i.e. CEM V/A) but lost 3% of steel volume because it was less cracked than V/A-2
Summary
Chloride-induced corrosion of steel reinforcement is a common cause of deterioration for reinforced concrete structures [1]. The tolerable chloride content for corrosion initiation is influenced by characteristics of the steel/concrete interface and of the concrete environment, such as by macro-pores, interfacial air voids and cracks [3,4]. Some studies reported that defects at the steel/concrete interface (SCI) are required for initiation of corrosion of the reinforcement [5,6,7,8]. Many studies have been conducted on the influence of interfacial defects for chloride-induced corrosion [4,5,6,7,8,9,10,11,12], on-going investigations and discussions on the topic highlights the importance to clarify if, and how, interfacial voids may affect initiation and propagation of corrosion of steel in concrete
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