COMBINED CHLORIDE PENETRATION AND CARBONATION: EVALUATION OF ELEMENT DISTRIBUTION AND THEIR MODEL

Combined chloride penetration and carbonation in concrete is a very common and severe situation. One of the main critical processes is believed to be that the carbonation process releases bound chlorides, which increases the risk for reinforcement corrosion. A novel method to measure quantitatively both chloride and carbon in cement hydrates has been developed based on EPMA. The results from these measurements are used to develop a new strategy for modeling chloride binding which accounts also for CO₃² present in pore solution. The binding of chlorides are, further, assumed to be assigned to different cement hydrates with its own characteristics in terms of binding capacity and non-linear features. The approach is tested using a multi-species diffusion model developed recently. The results from the measurements and the calculation states that the almost always occurring ‘peak’ behavior of the chloride profile at outer most part of concrete cover is due to carbonation releasing some of the bound chlorides from the chloride bearing cement hydrates.

• INTRODUCTION

• THE PROCESS OF CHLORIDE BINDING AND CARBONATION

• MEASUREMENTS ON COMBINED CARBONATION AND CHLORIDE ACTION

• EXPERIMENTAL RESULTS

• A MODEL FOR COMBINED CARBONATION AND CHLORIDE ACTION

• CONCLUSIONS

• REFERENCES