Corrosion Behavior of Corrosion-Resistant Steel Reinforcements in High and Ultra-High Performance Concrete in Chloride Attack Environments
Corrosion of reinforcing steel is one of the most important concerns for reinforced concrete (RC) structures. The use of corrosion-resistant steel reinforcements and advanced concrete is one potential solution. This dissertation presents the research findings of the corrosion behavior of corrosion-resistant steel reinforcements (epoxy coated, high chromium steel, and stainless steel reinforcement) in high performance concrete (HPC) and ultra-high performance concrete (UHPC) in chloride attack environments. Additionally, this dissertation presents service life prediction and life cycle cost analysis of RC structures made with different types of concrete and reinforcements.
Firstly, an experimental program was conducted to investigate the corrosion performance of the corrosion-resistant reinforcements in both conventional and advanced concrete. The corrosion potential, corrosion rate, and reinforcement mass loss of column specimens were monitored regularly over 24 months in an accelerated aging environment, and the degradation of the axial-load-carrying-capacity of the columns over time was also obtained and discussed. Findings indicate that corrosion-resistant reinforcements exhibit significantly improved corrosion performance. Additionally, HPC and UHPC provide robust protection to the embedded reinforcements, showing lower corrosion rates than that in conventional concrete. Significantly, UHPC showed supreme durability performance: no corrosion was detected for all types of reinforcements in UHPC specimens.
Secondly, an analytical model was developed to predict the axial load – axial shortening relationship of the corroded circular RC columns. The analytical model considered the influence of reinforcement corrosion on the reduced engineering properties of reinforcement, the weakening of the confinement effect on core concrete, and the deterioration of cover concrete. The analytical model showed reasonably accurate predictions when the analytical modeling results were compared with the experimental data in this study.
Furthermore, a service life prediction model for RC structures in chloride attack environments was synthesized, improved, and extended to the advanced materials. The chloride diffusion model and the corrosion rate model were verified with the experimental data from the independent literature and this study. In addition, the service life of RC structures made with different types of concrete and reinforcements in different environments were predicted and compared.
Lastly, the life cycle cost analysis of an RC bridge column for 100 years of service life in different environments was conducted. The RC column was designed using different types of concrete and reinforcements to meet the same design requirements. The initial material cost, repair cost, and life cycle cost of the RC columns were evaluated and compared.