Reevaluating the Significance of Concrete Cover Depth in Mitigating Carbonation-Induced Corrosion Damage

Abstract

The current European durability design codes primarily aim to prevent reinforce- ment corrosion induced by carbonation by focusing on inhibiting carbonation of the con- crete cover. This approach underpins current codes with exposure classes, assessing con- crete performance primarily based on carbonation resistance. Establishing limit states with practical relevance, such as concrete cracking, is essential to optimize material resource utilization. However, reliable models for predicting cover cracking time are currently lacking. Moisture conditions at the reinforcement depth are crucial in controlling corrosion rates. Because of that, another vital indicator for preventing structural damage from carbonation-induced corrosion is the concrete cover's ability to re- strict moisture ingress through the carbonated microstructure to the rebar depth. The current stringent durability design approach for carbonation may impose excessive and potentially ineffective requirements, particularly on modern cementitious binders with low clinker content, aimed at reducing carbon emissions. The current approach could therefore signif- icantly impact the overall global warming contribution of concrete, given that reinforced concretes structures subjected to carbonation-induced damage account for a substantial 60- 70% share. Maintaining the highly conservative limit state prevents widespread application of modern binder types and limits the construction sector's contribution to the UN Sustain- ability Development Goals. In the meantime, i.e., until such time when more rational design approaches are developed, verified and implemented, immediate benefits can be gained by implementing simple design strategies, such as thoroughly evaluating the chosen exposure class for various structural elements during the design phase to minimize environmental impact. This paper addresses this thematic by critically examining existing durability de- sign rules and proposing revisions to support sustainable solutions for the construction of reinforced co