Uncertain Factors Relating to the Prediction of Corrosion-induced Cracking of Concrete Cover

Rebar corrosion is a main cause affecting the durability and safety of reinforced concrete structures. Many mathematical models (empirical and analytical models) have been proposed to predict the corrosion-induced cracking of concrete cover over the recent decades. These models have differences in many aspects, such as constitutive laws for cracked concrete. However, each of them claimed that it could well agree with the test data. This may be due to the fact that a small amount of test data were used to verify their models. Besides, there are many uncertain factors such as the rust volumetric expansion factor and elastic modulus relating to these predictive models, which seriously weaken their effectiveness and accuracy. Thus, in this paper, the predictive performances of various mathematical models are tested by collecting an amount of test data. After that, the uncertain factors are summarized, and the reasons are analyzed though reviewing relevant knowledge in various literature. It is found that different performances are obtained for different mathematical models and test data. These uncertain factors involve many fields, such as electro-chemical factors (corrosion current density, corrosion current efficiency, corrosion rate, loading effect of corrosion current), rust properties (rust volumetric expansion factor, rust elastic modulus), long-term behavior of concrete (creep coefficient), rust penetration into concrete (amount of rust penetrated into concrete pores and cracks) and corrosion morphology. These uncertain factors are raised due to either the limit of experimental techniques, the discrepancy of parameter values, time-dependent properties, or the lack of detailed environmental information. In addition, other factors are too complex to be delicately taken into account, which have to be ignored in the predictive models. Through parameter analysis, it is found that these factors have large effects on cracking time of concrete cover. Prospective modifications of these factors are suggested, and more detailed and systematic tests should be carried out by using novel and sophisticated apparatuses in future.