Concrete cover cracking and service life prediction of reinforced concrete structures in corrosive environments

Crack initiation of concrete cover due to corrosion defines the end of functional service life where repair or replacement is required for corroded reinforced concrete (RC) structures. This study provides a comprehensive and critical analysis for the analytical and numerical models of corrosion-induced cover crack initiation for both uniform and non-uniform corrosion. Parametric studies are conducted to investigate the effects of different factors on crack initiation time and crack propagation patterns using a thermal analogy approach defined in three dimensional nonlinear finite element (FE) models. The results show that the type of corrosion products, thickness of interfacial transition zone and rate of corrosion are the parameters that affect crack initiation time the most significantly. The developed FE models are able to study crack initiation and propagation for both uniform and non-uniform corrosion and quantify the extent of concrete damage due to cracks. The FE results show that crack patterns under uniform and non-uniform corrosion differ. Under uniform corrosion, the major crack occurs vertically in the cover. But under non-uniform corrosion, major cracks form diagonally at the location of the pit in the cover. The vertical crack appears later and then becomes the third major crack. The results also show that non-uniform corrosion causes high concentrated pressure at the pits which would lead to earlier cover cracking. It is shown that assuming uniform corrosion may result in non-conservative service life estimation. The efficiency and applicability of the existing empirical models have been analyzed using the outcomes from the finite element models. Recommendations on how to select proper models to estimate crack initiation time have been provided. The outcome of the research provides a reliable approach to predict corrosion-induced cover crack initiation and propagation for RC structures.