SIMULATION FOR CORROSION CRACKING OF COVER CONCRETE IN REINFORCED CONCRETE STRUCTURES

摘要

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.