Unravelling the interplay between steel rebar corrosion rate and corrosion-induced cracking of reinforced concrete

TL;DR

This paper investigates the relationship between steel rebar corrosion rates and cracking in reinforced concrete, proposing a new model that aligns accelerated testing results with natural corrosion conditions to improve durability assessments.

Contribution

It introduces a corrosion-induced cracking model accounting for rust composition variability, validated against experimental data, and provides a correction factor for accelerated test extrapolation.

Findings

Model accurately predicts corrosion cracking under natural conditions.

Good agreement between simulation results and experimental data.

Proposes a crack width correction factor for accelerated testing.

Abstract

Accelerated impressed current testing is the most common experimental method for assessing the susceptibility to corrosion-induced cracking, the most prominent challenge to the durability of reinforced concrete structures. Although it is well known that accelerated impressed current tests lead to slower propagation of cracks (with respect to corrosion penetration) than in natural conditions, which results in overestimations of the delamination/spalling time, the origins of this phenomenon have puzzled researchers for more than a quarter of a century. In view of recent experimental findings, it is postulated that the phenomenon can be attributed to the variability of rust composition and density, specifically to the variable ratio of the mass fractions of iron oxide and iron hydroxide-oxide, which is affected by the magnitude of the applied corrosion current density. Based on this hypothesis, a corrosion-induced cracking model for virtual impressed-current testing is presented. The simulation results obtained with the proposed model are validated against experimental data, showing good agreement. Importantly, the model can predict corrosion-induced cracking under natural conditions and thus allows for the calculation of a newly proposed crack width slope correction factor, which extrapolates the surface crack width measured during accelerated impressed current tests to corrosion in natural conditions.