Model for cover cracking due to rebar corrosion in RC structures

Assessment of structural behavior of corrosion affected structures is an important issue; which would help in making certain decisions pertaining to the inspection, repair, strengthening, replacement and demolition of such structures. Depending on the level of oxidation of metallic iron, corrosion products may have much greater volume than the original iron which gets consumed by the process of corrosion. This volume expansion is mainly responsible for the through thickness cracking of the cover concrete; which would indicate the loss of service life for the corrosion affected structures. The paper presents an analytical model to predict the time required for cover cracking and the weight loss of reinforcing bars in corrosion affected reinforced concrete structures. The proposed model also incorporates the modeling aspects of the residual strength of cracked concrete and the stiffness contribution from the combination of reinforcement and expansive corrosion products. An attempt has also been made to arrive at reasonable estimates of the various parameters in the model related to the composition and properties of expansive corrosion products based on the available published experimental data. It has been found that the model is quite capable of providing the estimates of predicted time to cover cracking and weight loss of reinforcing bars that are in reasonably good agreement with the experimentally observed values as well as the analytical predictions of other researchers. It has also been found that both predicted time to cover cracking and weight loss of reinforcing bars are significantly influenced by tensile strength of cover concrete, annual mean corrosion rate and modulus of elasticity of reinforcement plus corrosion products combined.