Enhancing microstructural properties and chloride resistance of seawater-mixed steel fiber-reinforced mortars through glass powder modification

Abstract This study investigates how glass powder modification enhances steel fiber-reinforced mortar (SFRM) performance in marine environments, with focus on microstructural properties and chloride resistance. We developed a customized image segmentation technique that combines K-means clustering with concentric strip analysis to characterize the fiber–matrix interface. Results showed that replacing 25% of cement with glass powder reduced the interfacial transition zone thickness from 45 to 35 μm and decreased surface porosity from 95 to 85% after 28-d curing. The pozzolanic reactions generated additional C–S–H phases and modified phase assemblages, enhancing chloride resistance and increasing interfacial microhardness by 183.3 MPa. During wet–dry testing, glass powder-modified specimens showed 15–25% lower chloride concentrations and delayed corrosion initiation by 3–6 cycles in seawater-mixed specimens. This work provides both a testing methodology for fiber–matrix interface analysis and practical guidelines for improving SFRM durability in marine construction through waste glass utilization.