Comparative Analysis of Corrosion-Resistant Reinforcements in Concrete Structures

Thesis Abstract

This study addresses the progressive degradation of reinforced concrete structures caused by corrosion under aggressive environmental conditions, evaluating the performance of corrosion-resistant reinforcements as a sustainable mitigation strategy. The aim is to compare the long-term durability, service life, and life-cycle costs of alternative reinforcement materials—fibrereinforced stainless steel (Ferritic-Austenitic stainless bars), epoxy-coated steel, galvanized steel, and fiber-reinforced polymer (FRP) bars—relative to conventional steel reinforcements in varying exposure zones. The objectives are (1) to quantify corrosion initiation and propagation rates under chloride-rich and carbonation-dominated environments; (2) to assess mechanical performance degradation, including yield strength, ultimate tensile strength, and flexural capacity, over accelerated and natural exposure periods; (3) to evaluate durability indices and service-life predictions using mechanistic models, and (4) to conduct a comparative life-cycle cost assessment incorporating material, maintenance, and retrofit expenses. The methodology adopts a mixed-methods approach under a pragmatic research design. The population comprises reinforced concrete specimens and full-scale beams fabricated with four corrosion-resistant reinforcements and conventional steel, totaling 240 laboratory specimens and 24 full-scale beams, exposed to controlled laboratory simulations and outdoor exposure for up to 36 months. Data collection employs electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), corrosion potential measurements, scanning electron microscopy (SEM) for microstructural analysis, mechanical testing (maturity-corrected compressive strength, split-tension, and flexural tests), and nondestructive evaluation via ground-penetrating radar (GPR). Complementary data include field-case histories from 12 structures across coastal and industrial regions where corrosion-resistant reinforcements were implemented, yielding 54 relevant performance indicators. Validity and reliability are ensured through standardized test protocols (ASTM and ISO), calibration of instruments, and inter-laboratory cross-validation for a subset of samples. Data analysis integrates both quantitative and qualitative strands (i) regression analysis and analysis of variance (ANOVA) to compare corrosion rates, residual strengths, and deflections across reinforcement types; (ii) survival analysis to estimate service life under different exposure scenarios; (iii) life-cycle cost analysis (LCCA) incorporating net present value (NPV) and sensitivity analyses on material costs and retrofit intervals; (iv) Bayesian updating to refine deterioration models as data accrue; and (v) thematic analysis of field-case narratives to contextualize performance with construction practices and environmental variables. Theoretical framing draws on corrosion science theory, the reliability-based design philosophy, and the theory of total cost of ownership, with explicit reference to the Chloride-Induced Corrosion Model and the Elastic-Plastic Fracture Mechanics approach for structural assessment. Expected findings indicate that corrosion-resistant reinforcements exhibit significantly lower corrosion rates in chloride environments (p < 0.01) and superior residual mechanical properties after 36 months of exposure, with FRP bars showing the highest corrosion resistance but lower stiffness compared to steel composites. Epoxy-coated and galvanized steels are anticipated to offer moderate improvements with cost trade-offs. The study is expected to reveal that life-cycle costs favor corrosion-resistant reinforcements in high-corrosion zones when retrofit and maintenance costs are considered, despite higher initial material prices. The contribution to knowledge includes (i) a comprehensive, experimentally validated comparative performance framework for corrosion-resistant reinforcements in concrete, (ii) robust deterioration models suitable for reliability-based design and service-life prediction, and (iii) actionable guidelines for selection criteria, retrofit planning, and maintenance strategies tailored to exposure conditions. The main conclusion anticipates that for coastal and industrial climates with high chloride exposure, corrosion-resistant reinforcements yield superior long-term durability and lower life-cycle costs, particularly FRP and Ferritic-Austenitic stainless configurations, underpinned by validated models and field data. Recommendations include developing region-specific design guidelines that integrate durability indices with probabilistic service-life predictions, standardizing inspection intervals using nondestructive techniques, and pursuing further research on long-term behavior under dynamic loading and fire exposure, as well as exploring hybrid reinforcement systems to optimize performance and cost.