Abstract: Based on the theory of elasticity and Bazant’s physical model， the loop stress in concrete cover was modified correspondingly by introducing the concept of tensile damage， and models of critical corrosionexpansion stress and reinforcement corrosion rate were built at the moment when the concrete cover began to crack. By considering the filling effect of corrosion products in clearance between reinforcement and concrete and in the cracks， focus was given on the influences of the reinforcement diameter， concrete cover thickness and corrosionexpansion coefficient on the critical corrosion rates under 3 different loop stress conditions. These 3 conditions are proposed as perfect elasticity， Bazant model and tensile damage hoop stress， respectively. The results show that the critical corrosion rate decreases with the increase of the bar diameter， and increases with the increase of concrete cover thickness and corrosionexpansion coefficient. The critical corrosion rate in perfect elasticity is higher than that in Bazant model and in tensile damage. Finally， by comparing with Morinaga’s models， the models introduced in this paper are proved to be reasonable.

Key words: cover cracking, corrosion rate, corrosionexpansion coefficient, ideal plasticity, tensile damage