Enhancing Corrosion Resistance of Reinforced Concrete Using Ternary SCM Blends: Mechanical Performance, Durability Evaluation, and Microstructural Insights for Marine Infrastructure

Corrosion of steel reinforcement is one of the most critical durability challenges affecting reinforced concrete (RC) structures, especially in marine and chloride-rich environments. This study investigates the mechanical properties and corrosion resistance of RC incorporating supplementary cementitious materials (SCMs), including fly ash, silica fume, and ground granulated blast-furnace slag (GGBFS), used individually and in ternary combinations. Four concrete mixes—control (CM), fly ash (FA), silica fume (SF), and ternary SCM blend (TSCM)—were designed and evaluated. Mechanical properties were assessed through compressive, split tensile, and flexural strength tests, while durability performance was examined using porosity, water absorption, carbonation depth, half-cell potential, linear polarization resistance, and accelerated corrosion testing under 3.5% NaCl exposure. Microstructural characterization using SEM, EDS, and XRD provided insights into hydration products and pore refinement. Results showed that SCM incorporation significantly enhanced concrete performance. The TSCM mix exhibited the highest improvements, with a 15% increase in compressive strength and up to 35% reduction in water absorption compared to the control mix. Corrosion resistance improved substantially, as indicated by more than a 160% increase in time to first crack and a 75% reduction in corrosion rate. Microstructural analysis confirmed the formation of dense C–S–H/C–A–S–H phases and reduced calcium hydroxide content, resulting in lower chloride penetration and enhanced material integrity. Overall, the study demonstrates that ternary SCM blends provide superior mechanical and durability performance, making them highly suitable for RC structures exposed to aggressive marine environments. The findings contribute to the development of durable, sustainable, and long-lasting concrete systems for future infrastructure applications.