Expansion of the rust volume produced from corrosion creates the radial pressure pressing the cylindrical wall around reinforcing bars. To simulate this radial pressure from the expanding rust, a new experiment method is introduced. By this method, the mechanical device has to be embedded in each specimen during casting concrete. This device transfers the applied force and the displacement from vertical axis to the pressure and the displacement in radial direction. Therefore, the radial pressure and the displacement pressing the cylindrical wall around the reinforcing bars can be determined from the applied force and the displacement in the vertical direction. Two mortar specimens with different covering thickness, 50 and 90mm, were tested in order to examine the behaviors of the crack in the thinnest cover direction. The experimental results from this new experiment method are shown and compared with the calculated results of elastic, elastic-partially cracked, and fully plastic theory. In comparison, the experimental results of radial pressure were found to be higher than the elastic and the elastic-partially cracked but lower than the plastic theory. Furthermore, it was found that both normalized forms of the ultimate radial pressure and the ultimate radial displacement have linear relationships with non-dimensional cover thickness.

This study was conducted to propose a simulation model for corrosion cracking of cover concrete in reinforced concrete structures located on land and subjected to airborne chloride. Chloride penetration has been known to have great influences on the design corroded mass due to the fact that it changes the corrosion initiating time and corrosion rate. Accordingly, a chloride penetration model was proposed for reinforced concrete structures located on land. This model was verified with the drawn core of concrete specimens taken from structures that were free from the rain washout effect. In this study, the corrosion rate of reinforcing steel was also proposed by considering the change in degree of saturation in concrete due to environmental conditions. With the changes in the degree of saturation, the effective corrosion rate is changed according to three controlling factors: the conductivity of the concrete, the chloride concentration and the supply flux of oxygen. Therefore, the design corroded mass is the integration of the effective corrosion rate from the corrosion initiating time to the design time. Moreover, a numerical formula for limit corroded mass, which causes cracks in cover concrete, was developed and proposed. The accuracy of the formula was approximately 25% as compared to the experimental results of previous studies. Thus, the cracking time is the time when the design corroded mass is greater than the limit corroded mass. Additionally, the simulations at the time of cracking in cover concrete were compared with three actual reinforced concrete bridges subjected to airborne chloride.